THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
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Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]
Edition: Model Aviation - 2006/09
Page Numbers: 27,28,29,30,31,32,34,36,37,38,40,41
THE PROTOTYPE Consolidated B-24 Liberator first flew December
29, 1939, and was the most-produced American four-engine bomber of
World War II. The B-24D served in all theaters of the war and is best
remembered for its part in the raid on Ploesti Rumania oil refineries in
August 1943. However, it was used in many roles including fuel tanker,
antisubmarine, transport, naval patrol, and photo reconnaissance.
Currently there are only two B-24s flying and a small number in
museums in the US and in England. The B-24D was painted in many
different schemes ranging from olive drab and gray to the wildly
painted formation form-up aircraft, which gives modelers many
choices. I chose to model the D version since its nose has clean lines
that were cluttered up in later models by a gun turret and other
modifications.
My late flying buddy and Model Aviation Hall of Fame member
Owen Kampen flew the B-24D in training and said it was nice to fly in
contrast to the later models that were heavier and a handful to fly in
formation.
Being a devotee of small engines, this model was designed around
O.S. .10 FP power plants. Despite the B-24’s 82.5-inch wingspan, it is
not overly large.
CONSTRUCTION
Fuselage: Because of the need to fit some wing ribs later, it is best to
start construction with the fuselage. Cut the fuselage sides from 3/32 x 4
x 48 balsa and glue on the 1/32 plywood doublers that go from former 1
to the rear of former 8. Glue the 1/4 basswood wing saddle to the
plywood doubler.
Do not cut the fuselage sides to match the wing saddle at this
time, but draw a pencil line of the #3 wing rib centerline on the
outside of the fuselage sides. The wing hatch break line is at
formers 5 and 8 and involves extra formers that go down
only as far as the centerline of the wing ribs.
BY FRANK BAKER
September 2006 27
Glue 1/32 plywood to the rear of F5 and the front of F5A as well as
to the front of F8 and the back of F8A before you cut the formers. Be
sure to draw horizontal and vertical reference lines on both sides of all
formers.
The four 3/16 square stringers are used to hold the fuselage formers
together while the fuselage sides are glued to the formers. Add the 3/32
balsa sheet from F12 to F13 that supports the elevator.
Fabricate the nose-wheel steering mechanism from .032-inch
brass sheet, 5/32-inch-diameter brass tubing, and 1/8-inch music
wire. Bolt the mechanism to F3A and check to make sure it has a
good range of motion, and then glue F3A to F3 and glue in the 1/8
From this angle the very high-aspect-ratio wing is evident. The B-
24 was the most-produced American bomber of World War II.
Designed around the popular O.S. .10 engine, this is
a Liberator that won’t bomb a modeler’s budget
09sig1.QXD 7/25/06 1:02 PM Page 2728 MODEL AVIATION
Painted-on window and blister detailing makes building and finishing this model much
easier!
The four O.S. .10 FP engines fit snugly into their respective cowls, and the mufflers are
nestled neatly against the bottom of the nacelles.
Ominous-looking, isn’t it? Even though the B-24 is a large aircraft, the frontal area is
minimal. This is a great first multiengine subject to model.
balsa support plates.
Make the battery box from 1/8 sheet and
glue it in place. Use 1/4 plywood to make the
servo rails and install them to fit the servos
you will be using.
I used nylon tubing with a braided cable
inside to activate the rudders, elevators, and
nose wheel. Run lengths of nylon tubing
through the two sets of holes in the formers
from the servo compartment to approximately
2 inches to the rear of former 12. You could
also use pushrods, but you will need to plan
how you will install the pushrods.
Install the nylon antenna tube and use
silicone seal to hold it in place. Set the
fuselage aside at this point.
Empennage: Construct the stabilizer per the
plans and sheet the top of it with 1/32 balsa.
The elevators are made from soft 3/8 balsa and
joined with a CL-type elevator horn. Use a
long drill point or some other tool to make 1/8-
inch holes in all the stabilizer ribs at the
centerline of the ribs at the distance shown on
the plans.
Type: RC Sport Scale
Wingspan: 82.5 inches
Power: Four O.S. 10
FP engines
Flying weight:
6 pounds
Construction: Balsa
and plywood
Covering/finish:
Silkspan, silk,
modeling dope
09sig1.QXD 7/25/06 1:03 PM Page 28September 2006 29
This bomber looks extremely realistic in flight. It will turn heads at any field!
The finished framework shows the author’s clean workmanship. You can see the throttle-control pushrod routing and the radial
engine mount.
The aileron pushrod is shown. Notice the balsa plate in the one
wing bay where the pushrod is anchored.
The engine nacelles are built up and then planked with balsa. It’s a
light and easy structure to build.
The stabilizer is a built-up unit. This saves weight and adds
rigidity. It’s a builder’s project for sure!
The four wing-attachment tabs have been pop-riveted to the
outboard sides of the R-3 ribs.
09sig1.QXD 7/25/06 1:08 PM Page 2930 MODEL AVIATION
See page 191 for Full-Size Plans listing
09sig1.QXD 7/25/06 1:09 PM Page 30For straight runs of nylon tubing, I prefer
to use Du-Bro nylon antenna tubing that
comes straight rather than in coils. Put the two
sections of tubing in place and use silicone
sealer to hold them. Slip the braided cable that
is the length shown on the plans inside the
tubes and center it.
Install a small Z link of 1/16-inch-diameter
music wire in the rear arm of the nylon
bellcrank and a Z link with a 2-inch or longer
leg into the cross arm. Mount the nylon
bellcrank on a plate of 1/16 plywood cut to fit
between the two center ribs and slip it in
place, with the horn facing the bottom of the
stabilizer.
Put the bellcrank in the neutral position as
shown on the plans. Wrap the small Z link
and the cable with fine copper wire, and
solder them together.
Make the two rudder assemblies from 3/16
balsa and install the hinges. Glue the 1/32
plywood rudder-horn supports to both sides of
the rudders.
Make the rudder horns from .032 x 1/4-
inch brass strips by making a 90° twist, and
drill the rear 5/64-inch-diameter holes and the
front 1/16-inch-diameter hole. Use 2-56 bolts
to attach the horns to the inside of each
rudder. Use an X-Acto knife to hollow out the
rear spar and end rib of the stabilizer to allow
for inward movement of the rudder horn.
Install a small, L-shaped, 1/16-inchdiameter-
music-wire link into the rudder
horns. Drill a 3/16-inch-diameter hole in the
vertical fins as shown on the plans. Push
the vertical fin onto the peg and pin the
assembly to the stabilizer. Note that the
rudders tilt back slightly.
Check the rudders for roughly 3/4 inch
right and left motion. If necessary, remove
them and hollow out the stabilizer until they
move properly. Put the nylon bellcrank and
the rudders in their neutral positions.
Wrap the rudder L links and the cable
together with fine copper wire and solder
them. Use the bellcrank to move the rudders
and position the 1/16 plywood plate to get the
least friction, and then glue the plate in place
and solder the bellcrank nut to its bolt.
Make the rudder-horn covers from 3/32
balsa and pin in place. Check the rudder throw
again. When the range is proper, glue on the
covers and remove the rudder assemblies.
Install the nylon hinges in the elevators
and stabilizers, and glue them in place. The
1/32 sheeting will be glued to the bottom of the
stabilizer.
You will have to cut a hole in the bottom
sheeting to clear the bellcrank bolt and make a
slot for the rudder pushrod. Glue on the balsa
that fills the area between the two elevators.
Slip the rudder horns on the L links and solder
a small glob on the end of the L. Glue the
vertical fins to the stabilizer.
Cut two lengths of braided cable that will
reach from the elevator hinge line to the
middle of the servo rails. Use a short length of
3/32-inch-diameter brass tubing as a joiner, and
solder one cable to the rudder bellcrank Z
link. Solder a Z link to the second length of
cable and insert the Z link in the elevator arm.
Completing the Fuselage: Slip the rudder
and elevator cables inside their respective
tubes and pin the empennage in place. From
the servo compartment end, use the cables to
move the rudders and elevators to see if you
get the full range of motion.
You can slide the nylon tubes a bit if
necessary to get clearance. When things are
proper, use some clear silicone sealer to hold
the nylon tubes to the formers. Remove the
empennage and set it aside.
Slip a length of nylon tubing through
formers 4, 5, and 6. Solder a 1/16-inchdiameter-
music-wire Z link to a length of
cable, insert it into the steering arm of the
nose wheel, and feed the cable through the
nylon tube. Mount the rudder servo and add a
threaded connector and quick link at the servo
end of the cable.
Hook up your radio and use the transmitter
to run the nose wheel right and left. Make
sure it is properly coordinated with the rudder
movement.
Put a few small spacers of 1/64 plywood
between F5 and F5A, but do not glue them.
Place two or three very small spots of glue
between the outer edges of F5 and F5A to
hold them together. Do the same for F8 and
F8A, but do not use spacers.
Install the 1/8 square spruce stringers on
the top and bottom of the fuselage. I would
precut the three top stringers at the slit
between F5 and F5A and between F8A and
F8. The top and bottom of the fuselage will be
sheeted with 1/16 balsa, using a 4 x 48-inch
sheet for each quarter of the fuselage.
For the sheeting select medium A-grain
balsa that bends well across the narrow
dimension of the sheet. Making trial piecesfrom thin poster board will facilitate the
correct cutting of the balsa sheets.
Once a balsa sheet fits, it can be glued in
place using aliphatic resin glue. Be sure to
mark the wing-hatch separation lines on the
top sheeting so you can find the slit later on.
Once all the sheeting is in place, roughly
carve the nose and tail blocks to shape and
glue them in place. Now you can carve and
sand the nose and tail blocks to their final
shape. Drill a 5/8-inch-diameter hole in the
nose block for containing the lead nose
weight (if needed).
Cut a block for the cockpit area and fit
it between F3 and F4. Rough-cut it to
shape, hollow it to roughly 1/4 inch
thickness, and glue it in place.
To free the wing hatch, use an X-Acto
knife with a new blade. Slip it between the
plywood faces of F5 and F5A, and work it
around from one side to the other. Do the
same thing at the interface of F8A and F8.
Use a razor saw to cut along the pencil line of
the wing-rib centerline on the side of the
fuselage. You should be able to lift the wing
hatch out of the fuselage.
The fuselage construction may seem light
to some builders, but it is extremely rugged
once completed.
Wing: Take the wing-rib drawings to your
local copy shop and make two copies of the
ribs. Cut them approximately 1/8-inch
oversize from the paper, lightly spray contaccement to the back of the paper, and stick
the ribs to the balsa sheet. Note that rib 3 is
made from 1/8 birch plywood. Do not use
light plywood (poplar) for this rib.
Drill the 1/8-inch-diameter holes in ribs
1-9 for the motor-control tubing and ribs 1-
13 for the aileron control tubing. Once the
ribs are cut and drilled, remove the paper.
Save a rib 3 template for later use.
With a fine-point felt-tip pen, draw the
centerlines on both sides of all the ribs.
Draw vertical lines on ribs 12-16 at the front
of the rear wing spar and at the back of the
aileron LE.
Cut the four wing spars—roughly 1/2
inch longer than shown on the plans—from
1/8 x 1/4 spruce or basswood. The wings will
be built upside down, so pin the top spar for
the right wing to the plans.
Slip all the ribs (top down) except rib 3
onto the spar. Starting from the root rib,
glue the rib to the spar with slow-drying
glue.
On lengths of scrap balsa mark the
height of the rib centerline at the back edge
of the spar. Check the front and rear ends of
the rib-centerline marks to see that they are
the same height.
Put chunks of scrap balsa under the front
and rear parts of the rib to help hold the
rib’s position, and then pin the rib in place.
Repeat this process for each rib from the
root to tip rib. As you add each rib, sight the
front and rear centerline marks to see that
they form a straight line and that all the
centerlines are parallel.
Install the 3/8 x 1-inch LE. You may
want to slightly taper the LE before gluing it
in place. Glue on a 41-inch length of 1/16 x
11/2 balsa sheet to the rear of all the ribs
except 17 and use a square to make sure that
this sheet ends at the wing TE per the plans.
From rib 10 to 17 glue 1/16-inch verticalgrain
balsa shear webs between each pair of
ribs. Make sure the upper edge of the web is
flush with the lower edge of the wing-spar
slot.
Glue the bottom 1/8 x 1/4 spruce spar to
the ribs and the webs. Glue the LE 3/32 balsa
sheet that goes from the root rib to rib 11.
When the glue is dry, remove the wing
panel from the building board and use a
razor saw to cut ribs 12-16, first at the rear
of the aileron LE and then at the front edge
of the rear wing spar. Cut a 3/16-inch square
slot in rib 11 to accommodate the rear wing
spar stub.
Cut a 16-inch length of 3/8 x 3/4 balsa for
the aileron LE, and taper the thickness from
3/8 inch at the root to 3/16 inch at the tip. Pin
1/16 balsa spacers between this piece and the
3/16 x 3/4 rear wing spar.
Trim the 1/16 bottom TE to accommodate
the aileron LE. Glue the spar assembly to
both parts of the ribs, making sure that the
rear wing spar is centered and that the
centerlines of all the ribs form a straight
line. The rear spar should protrude
approximately 3/32 inch above and below the
ribs.
Glue the 1/16 x 1/4 balsa capstrips on ribs
12-17. Install the bottom 1/16 sheet that goesfrom 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.from 1 inch outside of rib 10 to 3/32 inch
inboard of rib 9. Draw a line on the front of
the wing’s LE that corresponds to the
centerlines marked on the ribs, and then use a
small plane to rough-shape the LE. Set the
right wing aside and build the left panel in the
same sequence.
When both wing panels are constructed,
make the dihedral brace from 1/16 plywood.
Find a hacksaw blade that will make a 1/16-
inch-wide cut, and make a vertical slot in ribs
1-10 that is flush with the back of the upper
and lower wing spars. The dihedral brace
should slip into the slot.
Slip both wing panels onto the dihedral
brace and check to make sure the top and
bottom edges of the dihedral brace are flush
with the tops of the spars. Also make sure the
number-1 ribs of the two panels fit together
properly.
When everything fits, glue the dihedral
brace into the two panels using slow-drying
glue. Be sure the rear sections of the ribs are
flush with the tops of the spars. Use an
incidence meter to make sure the wing is
straight, with no washout or washin. Stand off
and eyeball it to see that it is correct.
When the glue is dry, install all the 1/16
balsa sheeting on the bottom of the wing that
goes from 3/4 inch outboard of the left rib 6 to
outboard of rib 6 on the right wing. Glue the
capstrips on the bottoms of ribs 7 and 8.
Between F5 and F8 trim the fuselage sides
down to the wing saddle.
Set the fuselage on the workbench. Use
The KADET LT-40 is used by flying
instructors because it is known as "the
easiest to fly" trainer throughout the
world. Like all SIG KADETS, the LT-40
behaves perfectly in flight, with true
"hands off" stability on all axes.
Because the LT-40 is bigger than the
average .40 size trainer, it has a much
lighter wing loading, which lets it fly
slower! Slower speed gives the student
pilot more time to think and react
to what the model is doing, thus
making it easier to learn to fly R/C. A
true "Clark-Y" airfoil for better
penetration in the wind and a better
roll rate. This is one trainer that can
take you beyond learning just straight
and level flight!
Hand-crafted balsa and plywood
construction then meticulously
covered with SIG AeroKote® film. This
beautiful airplane takes no shortcuts in
quality of materials or workmanship.
This is an ARF You Can Be Proud Of!
SIG Manufacturing Company, Inc.
P. O. Box 520 • Montezuma, Iowa
www.sigmfg.com • 641-623-5154
Kadett LT--40 ARF:: Bestt Fllyiing Traiiner
Suggested Engine:
Aviastar AV-46
Order No. AVI46
Order No. SIGRC67ARF - Kadet LT-40 ARF - $131.99
Order No. SIGRC67 - Kadet LT-40 Kit - $91.99
* at Participating Dealers
SPECIFICATIONS:
Wingspan: 70 inches
Engine Required: .40-.46 2-stroke
.40-.54 4-stroke
Radio Required: 4 Channel, 4 servos
heavy objects to hold it with the fuselage sides
vertical to the workbench and the top of the
fuselage at 0˚.
Place the wing in the saddle and make sure
the wing is perpendicular to the centerline of
the fuselage, the wingtips are the same
distance from the surface of the workbench,
and the wing is at 2˚ incidence. It may take
carving and sanding the wing saddle, F6, and
F7 to accomplish a proper fit and positioning
of the wing, but it is critical.
Once everything is aligned properly, use a
soft pencil to mark where the outside of the
fuselage meets the wing. Draw the line on
both wing panels from LE to TE.
Make the four wing-attachment tabs from
.050-inch aluminum or .032-inch brass, and
pop-rivet them to the outboard sides of rib 3.
Measure where the tabs should go through the
bottom wing sheeting, and cut narrow 3/4-
inch-long slits at the pencil lines that were
previously drawn on the sheeting. Slip the
number-3 plywood ribs in position with the
tabs through the slits.
The metal tabs should fit snugly against
both sides of the fuselage. Modify the slits
until this is achieved, and then glue the two
ribs in place.
Glue the four 1/16 plywood plates inside
the bottom wing sheeting and up against the
outboard sides of the tabs. Use a pencil to
mark the holes of the metal tabs on the
fuselage sides and drill 5/64-inch-diameter
holes in the basswood wing saddle. Mount 2-
56 blind nuts on the inside of the saddle. You
use 2-56 x 1/2-inch socket-head bolts to hold
the wing onto the fuselage.
Nacelles and Throttle Controls: Cut the four
N4 firewalls from 3/16 birch plywood, and drill
the holes for the Dave Brown Products 15/19
engine mounts. Install the 4-40 blind nuts at
the back of the firewall. I use the 15/19
instead of the 09/10 mounts because they
allow you to move the engine a bit farther
forward from the firewall.
Drill the holes for the throttle control. Do
not drill the three 1/8-inch holes for the fueltank
pipes until the tanks have been
fabricated. Drill the holes for the 2-56 cowl
bolts, and install the blind nuts at the back of
the firewall.
Feed a 2-56 bolt through a piece of 1/16
plywood and bolt it to the lower hole. Use a
grinding wheel to cut the bolt off flush with
the back of the blind nut. Make eight of these
bolts and save them.
Coat the fronts of the firewalls with
thinned epoxy to fuel-proof them. Install the
engine mounts with 4-40 bolts and make sure
they pull the blind nuts into the plywood. Use
a grinding wheel to cut off the 4-40 bolts flush
with the backs of the blind nuts.
Build the four fuel tanks from K&S #254
tin sheet. Cut the four long strips and eight
side caps per the plans. Note that the fuel line
and vents go through holes drilled in the top
of the tank. Bend the four long tin strips per
the plans, and solder the tab that bends over
the top of the rear end of the tank.Use automotive 1/8-inch-outside-diameter
soft-copper tubing to make one set of vents
and a fuel line. Slip them through the holes in
the top of a tank and spot-solder them in
place. Slide the copper tubes through the
holes in a firewall. You may have to use a
small round file to slightly enlarge the holes,
but do not make them oversize.
Once the tubes have slid through the
firewall, make sure the tank is horizontal and
parallel to the centerline of the nacelle. Take
note of any changes in the bends of the tubes
and any changes in length that you feel are
necessary. Make three more sets of fuel lines
and vents. Final-solder all the copper tubing
into the tanks.
Custom-fit the sides of the tanks to each
individual tank. When the tanks are all
soldered, pressure-test them under water and
check for leaks.
Install all four tanks in the firewalls, and
use epoxy around the copper tubes at the front
and rear of the firewall. Put some glue
between the firewalls and the fronts of the
tanks.
Mark the centerline of each nacelle on the
LE and draw a line to the bottom TE that
slants 11/2˚ toward the root rib. Draw two
lines parallel to this line to locate the nacelle
supports. Cut the eight nacelle supports from
3/32 balsa and draw a centerline on each.
Set the wing at 2˚ incidence and then fit
the engine-nacelle supports so that their
centerlines are at 0˚. Stand the wing on its TE
and support it so that the main wing spars areparallel to the workbench.
Glue on the nacelle supports at their
respective 11/2˚ out-thrust lines. Notice that
forward of the LE the inside supports for
each nacelle are slightly longer than the
outside supports.
When the glue is dry, place an incidence
meter across the fronts of the supports and
check for 3˚ out-thrust. This measurement is
critical; the 3˚ is the secret to good engineout
behavior. Install former N5 in each
nacelle.
Block up the wing on the workbench with
the 2˚ incidence established and the wingtips
the same distance from the bench top. Use an
incidence meter to make sure the front edge
of each nacelle support is perpendicular to
the workbench; i.e., the engines are at 0˚.
Epoxy the firewall assemblies to the
nacelle supports and check again to ensure
that everything is aligned properly before the
glue sets. When viewed from the front, the
firewall’s horizontal centerline is parallel to
the ground—not to the wing dihedral.
Mount all four O.S. .10 FP engines on
their mounts. Cut the four 1/16 plywood
bellcrank mounting plates that fit between
ribs 5 and 6 and between ribs 9 and 10.
Mount a 90˚ nylon bellcrank on each plate,
and fit the assemblies in the wing; do not
glue them. Note that all pairs of bellcranks
point toward their respective wingtips.
Make the 3/32 plywood engine-control
servo-mounting plate. Install two 1/16-inch
threaded ball links on the servo wheel and
mount the servo on the plate. Cut out the
section of rib 1 as shown on the plans, and
glue in the mounting plate. Make sure the ball
joints line up with their respective rib holes.
Use your radio to put the servo in neutral, and
make sure the two ball links form a vertical
line.
Install the four lengths of nylon antenna
tubing in the wing-rib holes. Solder the brass
couplers that come with the ball links to one
end of each of the two lengths of cable that go
from the servo to the outer nacelles. Install the
nylon ball connectors on the couplers, feed the
cable through the nylon tubes, and attach the
nylon connectors to the servo ball links.
Use the radio to move the servo to its
limits of rotation and make sure the nylon
tubes near the servo do not interfere. Insert
lengths of nylon tubing from the bellcranks
through N2 and the firewall.
Make eight short Z links from 1/16-inchdiameter
music wire. Solder four of them to
lengths of cables that will be the throttle
controls. Insert the Z link into the bellcrank
arm and run the cable through the nylon tube
to the engine.
With the bellcrank held in the neutral
position shown on the plans and the throttle
arm in midrange, cut the cable to the
approximate length. Cut roughly 3/16 inch off
the hollow and threaded ends of a brass
coupler, and put on a nylon quick link. Install
the quick link on the throttle arm and the
cable.
Move the bellcrank back and forth to makesure the nylon tube does not restrict the
motion, and trim the tube as necessary. Cut
the cable to its final length and solder the
coupler to it. Things will go a bit easier if you
do one engine and then the remaining three.
Insert the remaining Z links in the rearfacing
arms of the bellcranks with the bottom
part of the Z link pointing toward the
wingtips. With everything in the neutral
position, bind the Z links to the cable with
fine copper wire. Shine a flashlight into the
throttle body to make sure the high and low
positions are the same for all four engines.
You may need to slide the Z links a bit to
align the bellcranks to the position shown on
the plans before soldering them to the cable.
Use the radio to run the throttles to their fully
open and closed positions, making sure the
nylon tubes do not interfere and that the angle
of the bellcrank mounting plates does not
cause friction.
It may be necessary to allow the ends of
the nylon tubes closest to the bellcranks to
move a bit in the adjacent wing ribs. The
same is true of the ends near the aileron servo.
When everything is moving properly, glue
the four mounting plates in position and use
silicone sealer to hold the nylon tubes in
place. The throttles should be set like those in
a sport airplane. Low throttle with high trim
should give low idle. Pulling the trim to full
low should kill the engine.
Ailerons: Cut the bottom 1/16-inch TE along
the slant line at rib 11 and inboard of rib 17.
Pull the aileron free from the rear wing spar.
Install the 3/8-inch hinge blocks. Mark the
positions of the hinges on the LE of the
aileron and the rear wing spar, and drill holes
for the 2-inch Robart hinge points. Use scraps
of 1/16 to make the aileron ribs that fit between
the existing ribs.
Add 1/8-inch ribs at the root and outer ends
of the aileron. Use 1/16 sheet to completely
cover the top and bottom of the aileron. Put
3/32 balsa on the outboard rear side of rib 11
and taper it to match the angle of the bottom
sheeting. Sand the aileron LE to its final
shape.
Make 3/16-inch square holes in the aileron
LE far enough back to place the hinge pin
where shown on the plans. Glue the hinge
points into the aileron. Cut a small square of
1/16 plywood and mount a small control horn
on it. At the location shown on the plans, cut
out enough of the aileron LE and a rib to fit
the plate flush with the bottom of the aileron,
and glue it in place.
To temporarily attach the ailerons to the
wings, push the front parts of the hinge points
into the rear spar blocks, leaving a 1/16-inch
space between the wing and the ailerons. Pin
the ailerons in the neutral position.
Make the aileron-servo mounting plate
from 3/32 plywood, and attach the aileron
servo to it. Cut out rib 1 per the plans and fit
the servo assembly between the left and right
number-2 ribs.
Slip Hobby Lobby nylon tubing (item
805) through the holes in the ribs from the left
wing to the right wing. The nylon tubing
should end approximately 1 inch from each
aileron horn. Cut a 1/8 x 3/8-inch slot in the 1/16
sheet that fits between the bottom capstrips of
ribs 14 and 15. Slip the sheet over the nylon
tubing and glue it in place.
At the center of the wing make sure the
tubing is level between the number-2 ribs.
Adjust the rib holes until the tubing is level,
and then cut out the center-section of the
nylon tubing per the plans.
Cut approximately 3/16 inch from the
hollow and threaded ends of a brass coupler,
and solder it to one end of the flex cable.
Attach a nylon quick link to the coupler.
Insert the braided cable in the nylon tubing
from the left to the right aileron horn, and clip
the quick link on the left aileron horn. You
may have to trim the nylon tubing so that the
aileron has full downward throw. Put the
ailerons back in neutral.
At the right aileron horn, cut off the cable
to fit a threaded coupler and a quick link, and
then clip it on the right aileron horn. Insert the
cable and solder the right coupler to the cable.
Make a small Z link from 1/16-inch-diameter
music wire and insert it in the upper arm of
the aileron servo. Wrap the link and cable
with fine copper wire, and solder them
together.
Use silicone sealer to glue the nylon
tubing to the inside of the 1/16-inch plates
between ribs 14 and 15. Remove the pins
holding the ailerons; they should remain at
neutral. Use your radio to cycle the aileron
servo. There should be 1/2 inch up and down
throw measured at the root end of the aileron.
When the engine and aileron controls
function properly, the remaining 3/32 and 1/16
sheet can be glued onto the top of the wing.
The remaining capstrips and the wingtip
blocks can be installed after cutting off the
wing spars outboard of rib 17. Install the balsa
aileron gap strips.Completing the Nacelles: The two outer
nacelles will be finished first. Glue formers
N7 and N8 in place. Pay attention to the slant
of the formers, which should match that of the
bottom of the wing.
Cut the side and bottom stringers from 1/4
balsa sheet and glue them in place. Use scrap
1/8 balsa to make stringers that fit between F8
and F7 that are halfway between the bottom
and side 1/4-inch stringers.
Sheet the nacelle with 3/32 balsa. I use thin
poster board to get a rough idea of how to fit
the sheeting to the nacelle. Fit poster board
from the middle of the top stringer to the
middle of one of the side stringers. Do the
same to the other side. When the poster board
fits reasonably well, use it as a pattern to cut
the 3/32 sheet.
Wet the sheet with hot water to which
ammonia has been added, and then fit both
balsa pieces to the top of the nacelle. Taper
the bottom sides of the rear parts of both
pieces so that they smoothly fit the curvature
of the top of the wing.
When both pieces fit properly, glue them
in place. When the glue has dried, trim the
sheets along the centerline of the side
stringers. Repeat this process for the two
bottom pieces, gluing on one side at a time.
The two inner nacelles are built in the
same fashion, but they also contain the
landing-gear assemblies.
Bend the main landing gear from 5/32-inchdiameter
music wire. Trace N6 onto the
various thicknesses of plywood as called outon the plans, and cut them approximately 1/8
inch oversize. Cut the slot in the 1/8 and 1/32
plywood pieces, and make sure the landinggear
strut fits in the slots, the axles point
toward the fuselage, and the slant of the
former matches that of the bottom of the
appropriate wing panel.
With the landing-gear struts inserted in the
slots, epoxy the two inner pieces and the two
outer 3/32 plywood pieces together and clamp
them until the glue sets. Trace N6 onto the
laminated plywood and cut it to shape.
Block up the wing upside down on the
workbench with a negative 2˚ incidence and
both wingtips touching the workbench. Place
the gear assembly on the bottom of the wing
and make sure the landing-gear leg is
perpendicular to the workbench, the axle is
parallel to the workbench, and the axle is
parallel to the line of the main wing spar.
Trim the plywood until it fits snugly
against the bottom sheeting. When the
assembly can be aligned properly, epoxy it in
place and check its position once more before
the glue sets.
Cut and install the 1/4-inch stringers and
former N7. Note that the side stringers
terminate against the bottom of the wing, and
the bottom stringer butts up to both sides of
N6. Cut some scrap 1/8 balsa to add the
stringers between N6 and N7.
Use the procedures described previously to
sheet the nacelles. Remove a half ellipse from
the sheeting at the half-round muffler cutout
on the firewall. Glue a piece of 1/32 plywoodbent into the cutout, and epoxy it in place.
Trim any excess above the balsa sheeting.
When the muffler is mounted, there should
be approximately 1/16 inch clearance
between the plywood and the muffler.
Cowls: Since the B-24’s cowls have
straight lines, they can be constructed from
wood. Cut cowl formers N1, 2, 3, and 3A
per the plans, and use a pencil to mark the
horizontal and vertical centerlines.
Make the four 1/32 plywood cowl strips.
Glue N2 to the back of N1 and make sure
there is at least 1/32 inch difference between
the outer edge of N2 and the outer edge of
N1. N2 is the smaller of the two formers.
Glue N3 to the front of the 1/16 plywood
N3A and drill the 5/64-inch-diameter holes
in N3A. Place a piece of kitchen plastic
film on the front of the firewall and bolt
formers N3-3A to the firewall with the
short 2-56 socket-head bolts.
Wrap the 1/32 plywood strip around
formers N2 and N3 with the overlap on the
right-hand side, even with the centerline of
the engine mounts, and check the fit.
Repeat this process using slow-drying glue,
using masking tape to hold the plywood
tight to the formers and the overlap
together.
Sight the cowl from the front and make
sure its centerline is vertical to the ground
and that the cowl is not twisted. To remove
the cowl when the glue is dry, access the 2-
56 bolts through the top or bottom of the
oil-cooler slots in N1. Make the remaining
three cowls in the same manner.
Mount the O.S. .10 FP engines on the
mounts, and locate the cutouts for the
cylinder head, muffler, and needle valve.
Notice that there is a strip of cowl between
the cylinder head and the muffler. Cut the
cylinder hole straight back to N3. Also drill
two small holes so that a screwdriver can
be used to attach the mufflers to the
engines after the cowls have been installed.
Cut and sand N1 to the shape the plans
show. The inner sections of the oil-cooler
slots are weak and should be coated with
cyanoacrylate glue, which will stiffen them
considerably. You will need to remove
some of the inside of N1 so that the throttle
arms have full motion.Finishing the Fuselage: Mount the wing on
the fuselage and attach it with the four
wing-tab sheet-metal screws. Block up the
fuselage and wing so that the top of the
fuselage is at 0˚ and the two wingtips are
the same distance from the workbench. Slip
the elevator and rudder cables into their
respective nylon tubes, and place the tail
assembly on the top of the two fuselage
sides.
Use an incidence meter to set the
stabilizer at 0˚. Determine how much of the
fuselage sides should be removed so that the
top of the stabilizer at the hinge line is flush
with the top of the fuselage. After the
stabilizer fits, ensure that it is perpendicular
to the fuselage centerline.
Sight from the front of the fuselage to
make sure the tips of the stabilizer are the
same distance above the wing. If they are
not, trim the fuselage sides slightly to fit,
but do not overtrim. You may want to glue
some 1/4 balsa inside the fuselage sides to
provide better support for the tail assembly.
Cut the rear turret fairing from 1/2 balsa
and fit it to the balsa that fits between the
two elevators and up against the rear turret.
Cut the fuselage to the front of the stabilizer
fairing from 1/4 balsa and trim it to fit, and
then install the fairings.
The last bit of construction is to fit the
hatch to the wing. Lay the number-3 rib
template on the rib centerline that was
drawn on the section of fuselage that was
removed along with the hatch.
Cut the sheeting at the top contour of the
rib approximately 1/8 inch closer to the
centerline. Slide the hatch down between
formers 5 and 8. The top of the hatch should
protrude above the top line of the fuselage.
Use a soft pencil to trace the contour of
the top of the wing on both sides of the
hatch. Carefully trim in stages up to this line
until the hatch fits the wing and is flush
with the top of the fuselage. When this is
achieved, glue the hatch to the wing and the
construction is finished.
Covering and Finishing: Being of the old
school, I like to use tissue, silk, and aircraft
dope to finish models. I put medium-weight
silkspan tissue on the fuselage and
empennage. I used silk on the wings.However, Mylar film can be nice to use since
the appropriate colors are readily available.
I doped the cowls inside and out. I sprayed
the upper surfaces with olive drab and the
bottoms with gray. I used an early-war
version of the US insignia, which was blue
circles with white stars cut from trim film.
I created the window frames for the nose,
cockpit, and rear turret by laying down 1/16-
and 3/32-inch tape and then spraying the
exposed areas with dark-gray dope. When the
tape is removed, the window frames are the
correct colors.
I carved forms for the astrodome and top
turret from basswood and mounted them on a
dowel in a baseplate. I heated .020-inch
acetate sheet to 250˚ in the kitchen oven and
pulled it down over the forms. This is even
easier if you have a vacuum box. I did not
bother to mount guns in the turrets since they
are the first things to get broken off.
Flying: Balance the assembled model with
radio, servos, and batteries installed, and
check to see if it balances at the point shown
on the plans. If it does not, put a mixture of
epoxy and lead shot in the vertical 5/8-inchdiameter,
2-inch-deep hole in the nose block.
Add enough lead in the hole to achieve the
CG shown on the plans. Then plug the hole
and paint the plug gray.
Since the fuel-tank vents are inaccessible,
put lengths of silicone fuel line on them that
reach approximately 1/2 inch beyond the front
of the cowl. They can be tucked back into the
cowl for flight. Be sure to flex both ailerons
up 1/8 inch as measured at the aileron root rib.
Each time I fly the B-24 I am asked how I
get all those engines started. My technique is
to start each engine, run it for roughly 30
seconds, and then shut it down. Then, starting
from the left engine, each engine will fire up
with a single flip of the propeller.
I have learned that the B-24 performs best
with Master Airscrew 8 x 4 propellers. The
model steers nicely on the ground, takes off
extremely quickly, and should be climbed at a
shallow angle. Once in the air, it flies rapidly,
has a level stance, and looks realistic.
Because of the short coupling, it is
important to coordinate rudder and ailerons
when making turns. To land, set up a wide
rectangular pattern, and on the base leg
throttle back enough to set up a moderate rate
of descent.
After passing over the edge of the flying
field on final, pull the power back to idle and
let the model glide in. Just before touchdown,
give a bit of up-elevator to flare and land on
the main wheels.
Because of the short nacelles, the fuel
tanks are rather small. Time them on a ground
run and then try to land well before the fuel
runs out.
If an engine quits in the air, the B-24 will
keep flying—a benefit of the 3˚ engine outthrust.
However, it behooves you to land as
soon as is practical. MA
Frank B. Baker
[email protected]