Lancair IV-P - 2009/09

THE LANCAIR SERIES of full-scale kit-built aircraft is
known for its fluid lines and outstanding performance. The
evolution of the four-place design to accept a 750-horsepower
turboprop engine expanded the performance envelope to an
amazing 370 mph cruise speed on 33 gallons of fuel per hour.
The narrow nose, elegant fuselage lines, and efficient
wing made it possible to design a unique-looking, semiscale,
electric-powered model that promised excellent
performance. Although the IV-P’s shapely fuselage lends
itself to fiberglass or foam construction, for a true scale look
we endeavored to build the model exclusively from arboreal
supplies, using traditional construction methods.
CONSTRUCTION
Trace, cut, and shape the wing ribs and fuselage bulkheads
from laminated balsa sheet. Using thin CA and a glass surface,
glue two sheets of 1/16 balsa, with the grain 90° to each other, to
create stock for the bulkheads.
As the plans indicate, there are plywood laminations on the nose ring
(1/64 inch), lower bulkheads #4 and #6 that face the wing, and center wing
LE (1/32 inch), and thumb-sized patches over the aft center portion of the
wing joint, to provide the structure with strength and durability.
Fuselage: The lower fuselage is built
upside-down over the plans, with the motor
mount submerged slightly into the building
board. Briefly soak the longerons in warm
water, to loosen them up to follow the plans
contour. Carefully pin the longerons to the
board over the plans.
Use a scrap 1/8 balsa stick to act as a
dummy tail post during fuselage
construction, but do not glue it in place. The
vertical stabilizer will eventually slide into
this gap.
Once dry, glue the bulkheads squarely
against the longerons, followed by the wing
crutch and lower longerons. The lower
longerons bend aggressively toward the
motor mount and must be preformed wet,
allowed to dry in place, and then glued. Use
epoxy for the motor mount and aliphatic
glue for the rest of the bulkheads.
Nose-side perimeters of bulkheads #2
and #3 and aft-facing perimeter #6 have thin
strips of soft 1/8 square balsa glued to them,
to provide increased adhesion area for balsa
planking.
Cover the upward-facing surface of the
battery floor with hook-and-loop fastener,
and glue it in place with epoxy. Once dry,
remove the lower fuselage from the board
and glue the upper bulkheads and dorsal
longeron in place.
The fuselage framework is spindly at this
point, so be careful as you use a long
sanding bar to gently bevel the bulkheads
and longerons to the fuselage’s curves,
leaving smooth, radiused surfaces to which
the planking will adhere.
Planking a fuselage takes time and effort,
but the end product is a work of art. Wear
gloves or barrier cream; you’ll get CA on
your skin during this process.
Employ a balsa stripper shimmed to
provide an approximate 60° angle on the
edge. Cut several dozen 7/16-inch-wide strips
from 1/16 balsa sheet.
Using thin CA and working from tail to
nose, glue the first strip midway over the
fuselage longeron. Carefully align the second
strip tightly and close to the first strip,
working slowly from tail to nose, stretching it
ever so slightly, placing it firmly against the
bulkheads. Apply microdrops of thin CA
every 1/2 inch or so, to glue the strips to each
other and to the bulkheads.
Apply two strips on the starboard side
and two strips on the port side, to prevent
warping the framework. Use the CA
sparingly, and occasionally go back from the
inside of the fuselage to glue loose planking,
and double-glue all strips to the bulkheads.
Continual strips can run on the sides from
the tail to the motor mount, using the watersoak/
prefitting trick to help shape the pieces
where necessary.
The planking strips will eventually be
unable to make the sharp, twisting bend
toward the motor mount. This is expected,
and the remaining open areas will be
planked on the top of the nose from
bulkhead #3 to the motor mount, and
eventually from the bottom of the nose from
bulkhead #4 to the motor mount. This
requires custom fitting, patience, a sanding
block, and trial and error, but it is highly
rewarding.
Plank the top of the nose starting at the
center and working out to the sides,
eventually custom-fitting strips to fill the
gaps. Wait to plank the lower nose and
lower aft fuselage until after you have
mounted the wing.
Five continual strips can be planked
down the center of the upper fuselage
between bulkhead #8 and bulkhead #3, but
eventually the compound curves become too
severe. The upper empennage is planked
with individually fitted pieces, and the
windshield edges are formed from triangleshaped
balsa-sheet inserts.
When you have completed the planking,
gently sand the high spots with 400-grit
paper to yield a smooth finish. Fill large
gaps with scrap balsa strips using sandable
aliphatic glue, and remedy imperfect
contours and small gaps with lightweight
spackling compound and more sanding. You
don’t want to sand too much, because the
sheeting is already relatively thin.
Size and shape the 1/32 plywood doublers
for the rudder and elevator to the servos you
intend to use, glue them onto the aft fuselage
as shown, and use a rotary tool to remove
the balsa sheet from the center of the cutout.
Make sure that the cutouts and servo screws
do not cut into the fuselage longerons.
I used Ernst pushrod exits as cooling
intakes on the lower nose and made an
appropriately sized cooling-air exit hole in
the ventral aft fuselage.
Mount the motor, propeller, and spinner
into the fuselage, and use 1/4 balsa sheet
with a 1/64-inch plywood lamination to
make an oversize nose ring. With the
plywood facing the spinner, sand the nose
ring to smoothly fair the fuselage to the
spinner. Cut a gap in the lower nose ring to
allow access to the propeller-adapter
setscrew.
Employ a light-plywood spacer to
position the aft wing mount, as plans show,
and bolt the mount to bulkhead #6, making
sure it is 1/8-1/4 inch below fuselage skin
level, to allow the wing TE to be flush with
the lower aft fuselage skins. Use scrap 1/32
plywood sheet on the aft side of bulkhead
#6 to form a strong base for the mount nuts
and washers.
Wing: The wing construction is
straightforward, using the dihedral gauge to
cant the top of each #1 rib out by 3°, giving
6° of final dihedral. The ribs must sit
squarely over the lower spar and the ventral
skegs must sit hard against the board, to
give the wing ribs proper angle and
washout. You will trim off the skegs before
you apply the lower sheeting.
Use diagonal braces to strengthen the
butt-joint corners where the LE and TE
meet ribs #1 and ribs #8. Add the small
balsa doublers to reinforce the hinge areas.
Minimally and gently smooth the ribs with
a sanding bar, and sheet the wing with 1/32
balsa. Add the wingtips made from soft
balsa blocks.
The aileron rods are fitted into grooves
cut into the unfinished wing’s TE, and then
the TE is fitted and glued in place. Position
the aileron servo off center, to preserve the
center ribs’ strength, and set it high on scrap
balsa/plywood pedestals to prevent the
servo screws from penetrating the wing spar
or the servo base from sticking through the
bottom of the wing. Attach the ailerons with
Robart 1/2A pin hinges, and seal the gap on
the top surface with strips of covering.
Sand the wing and ailerons gently and
minimally (remember that the wing skins
are thin), to obtain a smooth contour. Epoxy
the wing halves together using the main
spars as a guide for alignment. I used 1.5-
inch-long, 0.25-inch-wide strips of 1/32
plywood to laminate the upper and lower
spar joints.
Adhere the plywood doublers on the aft
wing joint, sand the centerline face of the
LE square, and epoxy the fuselage-wide 1/32
plywood sheet to the LE. Glue triangular
hard-balsa shims behind the LE plywood
facing, to add some structure to receive the
wing-mounting dowels.
Carefully sand the fuselage sides over
the wing crutch, to achieve a wing contour
with minimal gap between the top wing
surface and the fuselage side at the wing
crutch. Align the wing centerline joint with
the centers of the lower fuselage longerons.
Using the wing-mount hole as a guide,
mark, with a pencil lead, the wing-bolt
position from inside the fuselage. Drill the
appropriate hole through the wing, and bolt
the wing into the fuselage. Shim or grind
the mount as required to ensure that the
wing sits on the mounting bracket and is not
crushing the fuselage sides or wing surface.
Double-check the LE centerline with the
fuselage longeron and make sure that the
wing sits symmetrically in the saddle by
comparing it to a dummy horizontal
stabilizer that is temporarily glued across
the stern longerons.
Once you are satisfied with the
alignment, use an extra-long 1/8-inchdiameter
drill bit to bore the first hole
squarely through bulkhead #4 and into the
wing. Put a temporary dowel through hole
#1 to hold the wing in place, double-check
alignment, and drill hole #2.
Remove the wing and glue 1/8-inchdiameter
hardwood dowels into the holes.
Toughen the peg holes in bulkhead #4 with
thin CA, and then ream them clean.
Now you can plank the lower nose
fuselage and sheet the lower empennage
with cross-grain balsa. Build up the lower
wing fairing under the fuselage using a few
1/4-inch-wide by 1/16-inch-thick balsa strips
glued to the lower wing surface.
Sand these pieces flat before gluing a
cross-grain balsa filler on top of that.
Smoothly fair and/or fill the underside of
the wing into the lower fuselage.
Final Assembly: Cut the tail feathers from
1/8 balsa sheet using a 1/8-inch-square by 3-
inch-long hardwood stick or piano-wire
joiner to connect the elevator halves. I used
Granite State gapless iron-on hinge for the
elevator and rudder, with handmade 1/16
plywood horns epoxied into the moving
surfaces. The lower vertical stabilizer’s LE
slides into the groove in the aft end of the
fuselage.
The choice of power system and
batteries will dictate where you will mount
the batteries. There is plenty of room inside
the fuselage to mount the electrical
components, including elevator and rudder
servos, if desired.
For the prototype, the relatively heavy
cobalt motor, propeller, and spinner
mounted so far in front of the CG that it
necessitated placing the servos in the far
end of the tail, to avoid dreaded ballast.
Covering: We covered the prototype in
white and red MonoKote. The windows
were painted on with gray acrylic paint
outlined in black. Painting mistakes are
easy to remedy with a wipe of denatured
alcohol.
The turbine exhaust shrouds are handcarved
scrap balsa that was painted and
glued onto the fuselage with canopy glue.
Although the IV-P is a civil aircraft, the red
tail honors the Tuskegee Airmen.
Flying: With the CG and control throws set
per plans, with one click of up-elevator the
Lancair can be hand launched with a
moderate overhead throw at the horizon. It
powers out of the launch well and is
responsive in all axes.
The wing provides excellent inverted
and outside performance. The prototype
demonstrated a nice rate of speed, but a
modern brushless power system would
turn this airplane into a long-duration
screamer.
The propjet should be flown at a
shallow angle into a landing. You should
wait to attempt full-stall landings and lowlevel
aerobatics until you are accustomed
to the model’s performance envelope, wing
loading, and stall speed.
Even though the IV-P takes builder’s
skill and more time than some other
projects, the payoffs are an expansion of
your skill set and a sleek, distinctive, highperformance
airplane that is probably rare
to see at your airfield.
Gus Morfis
[email protected]
Tom Fey
[email protected]
MA Flies the Propjet: We were thrilled to
accept the Lancair project from Gus and
Tom. During the discussion, the need for
in-flight photos came up; the solution
offered was to ship the prototype to AMA
Headquarters. We accepted, of course.
We flew the model exactly as
described in the preceding and found the
performance reports to be spot on. We had
a blast flying the model with the brushedmotor
system and NiMH batteries. Call us
spoiled, but we couldn’t help but have
total confidence that a modern brushless
system and Li-Poly batteries would pump
this propjet even better into the sleek
speedster that its full-scale heritage
boasted.
Looking at what we had on hand, a sixpole,
2600 Kv inrunner helicopter motor
was exchanged for the Cobalt 400; it was
practically the same weight and size. The
ESC was exchanged for a brushless type
that included auto-detect programming
with Li-Poly cutoff protocols. We kept the
same 7 x 4 Master Airscrew propeller and
Du-Bro spinner.
The well-thought-out prototype flew
with the batteries right over the CG;
therefore, choosing the appropriate Li-Poly
was simply a matter of accommodating the
expected motor demand.
We settled on a 7.4-volt power source,
which tested on the bench to handle roughly
a 16-amp load. On hand was a 2400 mAh
10C Li-Poly battery that weighed roughly
half of the old 8.4-volt NiMH pack. We
dropped close to 2 ounces overall and
gained 50-65 watts of power. With smiles
all around, it was time to fly again.
The Lancair could be launched with
either an overhand or underhand toss. A
headwind actually helps a lot.
The extra power and lighter weight did
wonders for the friendly model. Pylon turns
were comfortable, as were any powerhungry
maneuver from level flight.
Shedding the bit of weight permitted a
landing that simulated a flop into the grass
rather than a skid.
Our final thoughts were that the Lancair
would suit any builder, no matter what power
choice was available; later changes are a
matter of plug-n-play. If a smooth runway is
at hand for you, the IV-P could be modified
for fixed (removable) landing gear. MA
Michael Ramsey
[email protected]
Sources:
Ernst Manufacturing
(503) 668-5597
www.ernstmfg.com
Robart
(630) 584-7616
www.robart.com
Master Airscrew/Windsor Propeller
(916) 631-8385
www.masterairscrew.com
Du-Bro
(800) 848-9411
www.dubro.com

THE LANCAIR SERIES of full-scale kit-built aircraft is
known for its fluid lines and outstanding performance. The
evolution of the four-place design to accept a 750-horsepower
turboprop engine expanded the performance envelope to an
amazing 370 mph cruise speed on 33 gallons of fuel per hour.
The narrow nose, elegant fuselage lines, and efficient
wing made it possible to design a unique-looking, semiscale,
electric-powered model that promised excellent
performance. Although the IV-P’s shapely fuselage lends
itself to fiberglass or foam construction, for a true scale look
we endeavored to build the model exclusively from arboreal
supplies, using traditional construction methods.
CONSTRUCTION
Trace, cut, and shape the wing ribs and fuselage bulkheads
from laminated balsa sheet. Using thin CA and a glass surface,
glue two sheets of 1/16 balsa, with the grain 90° to each other, to
create stock for the bulkheads.
As the plans indicate, there are plywood laminations on the nose ring
(1/64 inch), lower bulkheads #4 and #6 that face the wing, and center wing
LE (1/32 inch), and thumb-sized patches over the aft center portion of the
wing joint, to provide the structure with strength and durability.
Fuselage: The lower fuselage is built
upside-down over the plans, with the motor
mount submerged slightly into the building
board. Briefly soak the longerons in warm
water, to loosen them up to follow the plans
contour. Carefully pin the longerons to the
board over the plans.
Use a scrap 1/8 balsa stick to act as a
dummy tail post during fuselage
construction, but do not glue it in place. The
vertical stabilizer will eventually slide into
this gap.
Once dry, glue the bulkheads squarely
against the longerons, followed by the wing
crutch and lower longerons. The lower
longerons bend aggressively toward the
motor mount and must be preformed wet,
allowed to dry in place, and then glued. Use
epoxy for the motor mount and aliphatic
glue for the rest of the bulkheads.
Nose-side perimeters of bulkheads #2
and #3 and aft-facing perimeter #6 have thin
strips of soft 1/8 square balsa glued to them,
to provide increased adhesion area for balsa
planking.
Cover the upward-facing surface of the
battery floor with hook-and-loop fastener,
and glue it in place with epoxy. Once dry,
remove the lower fuselage from the board
and glue the upper bulkheads and dorsal
longeron in place.
The fuselage framework is spindly at this
point, so be careful as you use a long
sanding bar to gently bevel the bulkheads
and longerons to the fuselage’s curves,
leaving smooth, radiused surfaces to which
the planking will adhere.
Planking a fuselage takes time and effort,
but the end product is a work of art. Wear
gloves or barrier cream; you’ll get CA on
your skin during this process.
Employ a balsa stripper shimmed to
provide an approximate 60° angle on the
edge. Cut several dozen 7/16-inch-wide strips
from 1/16 balsa sheet.
Using thin CA and working from tail to
nose, glue the first strip midway over the
fuselage longeron. Carefully align the second
strip tightly and close to the first strip,
working slowly from tail to nose, stretching it
ever so slightly, placing it firmly against the
bulkheads. Apply microdrops of thin CA
every 1/2 inch or so, to glue the strips to each
other and to the bulkheads.
Apply two strips on the starboard side
and two strips on the port side, to prevent
warping the framework. Use the CA
sparingly, and occasionally go back from the
inside of the fuselage to glue loose planking,
and double-glue all strips to the bulkheads.
Continual strips can run on the sides from
the tail to the motor mount, using the watersoak/
prefitting trick to help shape the pieces
where necessary.
The planking strips will eventually be
unable to make the sharp, twisting bend
toward the motor mount. This is expected,
and the remaining open areas will be
planked on the top of the nose from
bulkhead #3 to the motor mount, and
eventually from the bottom of the nose from
bulkhead #4 to the motor mount. This
requires custom fitting, patience, a sanding
block, and trial and error, but it is highly
rewarding.
Plank the top of the nose starting at the
center and working out to the sides,
eventually custom-fitting strips to fill the
gaps. Wait to plank the lower nose and
lower aft fuselage until after you have
mounted the wing.
Five continual strips can be planked
down the center of the upper fuselage
between bulkhead #8 and bulkhead #3, but
eventually the compound curves become too
severe. The upper empennage is planked
with individually fitted pieces, and the
windshield edges are formed from triangleshaped
balsa-sheet inserts.
When you have completed the planking,
gently sand the high spots with 400-grit
paper to yield a smooth finish. Fill large
gaps with scrap balsa strips using sandable
aliphatic glue, and remedy imperfect
contours and small gaps with lightweight
spackling compound and more sanding. You
don’t want to sand too much, because the
sheeting is already relatively thin.
Size and shape the 1/32 plywood doublers
for the rudder and elevator to the servos you
intend to use, glue them onto the aft fuselage
as shown, and use a rotary tool to remove
the balsa sheet from the center of the cutout.
Make sure that the cutouts and servo screws
do not cut into the fuselage longerons.
I used Ernst pushrod exits as cooling
intakes on the lower nose and made an
appropriately sized cooling-air exit hole in
the ventral aft fuselage.
Mount the motor, propeller, and spinner
into the fuselage, and use 1/4 balsa sheet
with a 1/64-inch plywood lamination to
make an oversize nose ring. With the
plywood facing the spinner, sand the nose
ring to smoothly fair the fuselage to the
spinner. Cut a gap in the lower nose ring to
allow access to the propeller-adapter
setscrew.
Employ a light-plywood spacer to
position the aft wing mount, as plans show,
and bolt the mount to bulkhead #6, making
sure it is 1/8-1/4 inch below fuselage skin
level, to allow the wing TE to be flush with
the lower aft fuselage skins. Use scrap 1/32
plywood sheet on the aft side of bulkhead
#6 to form a strong base for the mount nuts
and washers.
Wing: The wing construction is
straightforward, using the dihedral gauge to
cant the top of each #1 rib out by 3°, giving
6° of final dihedral. The ribs must sit
squarely over the lower spar and the ventral
skegs must sit hard against the board, to
give the wing ribs proper angle and
washout. You will trim off the skegs before
you apply the lower sheeting.
Use diagonal braces to strengthen the
butt-joint corners where the LE and TE
meet ribs #1 and ribs #8. Add the small
balsa doublers to reinforce the hinge areas.
Minimally and gently smooth the ribs with
a sanding bar, and sheet the wing with 1/32
balsa. Add the wingtips made from soft
balsa blocks.
The aileron rods are fitted into grooves
cut into the unfinished wing’s TE, and then
the TE is fitted and glued in place. Position
the aileron servo off center, to preserve the
center ribs’ strength, and set it high on scrap
balsa/plywood pedestals to prevent the
servo screws from penetrating the wing spar
or the servo base from sticking through the
bottom of the wing. Attach the ailerons with
Robart 1/2A pin hinges, and seal the gap on
the top surface with strips of covering.
Sand the wing and ailerons gently and
minimally (remember that the wing skins
are thin), to obtain a smooth contour. Epoxy
the wing halves together using the main
spars as a guide for alignment. I used 1.5-
inch-long, 0.25-inch-wide strips of 1/32
plywood to laminate the upper and lower
spar joints.
Adhere the plywood doublers on the aft
wing joint, sand the centerline face of the
LE square, and epoxy the fuselage-wide 1/32
plywood sheet to the LE. Glue triangular
hard-balsa shims behind the LE plywood
facing, to add some structure to receive the
wing-mounting dowels.
Carefully sand the fuselage sides over
the wing crutch, to achieve a wing contour
with minimal gap between the top wing
surface and the fuselage side at the wing
crutch. Align the wing centerline joint with
the centers of the lower fuselage longerons.
Using the wing-mount hole as a guide,
mark, with a pencil lead, the wing-bolt
position from inside the fuselage. Drill the
appropriate hole through the wing, and bolt
the wing into the fuselage. Shim or grind
the mount as required to ensure that the
wing sits on the mounting bracket and is not
crushing the fuselage sides or wing surface.
Double-check the LE centerline with the
fuselage longeron and make sure that the
wing sits symmetrically in the saddle by
comparing it to a dummy horizontal
stabilizer that is temporarily glued across
the stern longerons.
Once you are satisfied with the
alignment, use an extra-long 1/8-inchdiameter
drill bit to bore the first hole
squarely through bulkhead #4 and into the
wing. Put a temporary dowel through hole
#1 to hold the wing in place, double-check
alignment, and drill hole #2.
Remove the wing and glue 1/8-inchdiameter
hardwood dowels into the holes.
Toughen the peg holes in bulkhead #4 with
thin CA, and then ream them clean.
Now you can plank the lower nose
fuselage and sheet the lower empennage
with cross-grain balsa. Build up the lower
wing fairing under the fuselage using a few
1/4-inch-wide by 1/16-inch-thick balsa strips
glued to the lower wing surface.
Sand these pieces flat before gluing a
cross-grain balsa filler on top of that.
Smoothly fair and/or fill the underside of
the wing into the lower fuselage.
Final Assembly: Cut the tail feathers from
1/8 balsa sheet using a 1/8-inch-square by 3-
inch-long hardwood stick or piano-wire
joiner to connect the elevator halves. I used
Granite State gapless iron-on hinge for the
elevator and rudder, with handmade 1/16
plywood horns epoxied into the moving
surfaces. The lower vertical stabilizer’s LE
slides into the groove in the aft end of the
fuselage.
The choice of power system and
batteries will dictate where you will mount
the batteries. There is plenty of room inside
the fuselage to mount the electrical
components, including elevator and rudder
servos, if desired.
For the prototype, the relatively heavy
cobalt motor, propeller, and spinner
mounted so far in front of the CG that it
necessitated placing the servos in the far
end of the tail, to avoid dreaded ballast.
Covering: We covered the prototype in
white and red MonoKote. The windows
were painted on with gray acrylic paint
outlined in black. Painting mistakes are
easy to remedy with a wipe of denatured
alcohol.
The turbine exhaust shrouds are handcarved
scrap balsa that was painted and
glued onto the fuselage with canopy glue.
Although the IV-P is a civil aircraft, the red
tail honors the Tuskegee Airmen.
Flying: With the CG and control throws set
per plans, with one click of up-elevator the
Lancair can be hand launched with a
moderate overhead throw at the horizon. It
powers out of the launch well and is
responsive in all axes.
The wing provides excellent inverted
and outside performance. The prototype
demonstrated a nice rate of speed, but a
modern brushless power system would
turn this airplane into a long-duration
screamer.
The propjet should be flown at a
shallow angle into a landing. You should
wait to attempt full-stall landings and lowlevel
aerobatics until you are accustomed
to the model’s performance envelope, wing
loading, and stall speed.
Even though the IV-P takes builder’s
skill and more time than some other
projects, the payoffs are an expansion of
your skill set and a sleek, distinctive, highperformance
airplane that is probably rare
to see at your airfield.
Gus Morfis
[email protected]
Tom Fey
[email protected]
MA Flies the Propjet: We were thrilled to
accept the Lancair project from Gus and
Tom. During the discussion, the need for
in-flight photos came up; the solution
offered was to ship the prototype to AMA
Headquarters. We accepted, of course.
We flew the model exactly as
described in the preceding and found the
performance reports to be spot on. We had
a blast flying the model with the brushedmotor
system and NiMH batteries. Call us
spoiled, but we couldn’t help but have
total confidence that a modern brushless
system and Li-Poly batteries would pump
this propjet even better into the sleek
speedster that its full-scale heritage
boasted.
Looking at what we had on hand, a sixpole,
2600 Kv inrunner helicopter motor
was exchanged for the Cobalt 400; it was
practically the same weight and size. The
ESC was exchanged for a brushless type
that included auto-detect programming
with Li-Poly cutoff protocols. We kept the
same 7 x 4 Master Airscrew propeller and
Du-Bro spinner.
The well-thought-out prototype flew
with the batteries right over the CG;
therefore, choosing the appropriate Li-Poly
was simply a matter of accommodating the
expected motor demand.
We settled on a 7.4-volt power source,
which tested on the bench to handle roughly
a 16-amp load. On hand was a 2400 mAh
10C Li-Poly battery that weighed roughly
half of the old 8.4-volt NiMH pack. We
dropped close to 2 ounces overall and
gained 50-65 watts of power. With smiles
all around, it was time to fly again.
The Lancair could be launched with
either an overhand or underhand toss. A
headwind actually helps a lot.
The extra power and lighter weight did
wonders for the friendly model. Pylon turns
were comfortable, as were any powerhungry
maneuver from level flight.
Shedding the bit of weight permitted a
landing that simulated a flop into the grass
rather than a skid.
Our final thoughts were that the Lancair
would suit any builder, no matter what power
choice was available; later changes are a
matter of plug-n-play. If a smooth runway is
at hand for you, the IV-P could be modified
for fixed (removable) landing gear. MA
Michael Ramsey
[email protected]
Sources:
Ernst Manufacturing
(503) 668-5597
www.ernstmfg.com
Robart
(630) 584-7616
www.robart.com
Master Airscrew/Windsor Propeller
(916) 631-8385
www.masterairscrew.com
Du-Bro
(800) 848-9411
www.dubro.com

THE LANCAIR SERIES of full-scale kit-built aircraft is
known for its fluid lines and outstanding performance. The
evolution of the four-place design to accept a 750-horsepower
turboprop engine expanded the performance envelope to an
amazing 370 mph cruise speed on 33 gallons of fuel per hour.
The narrow nose, elegant fuselage lines, and efficient
wing made it possible to design a unique-looking, semiscale,
electric-powered model that promised excellent
performance. Although the IV-P’s shapely fuselage lends
itself to fiberglass or foam construction, for a true scale look
we endeavored to build the model exclusively from arboreal
supplies, using traditional construction methods.
CONSTRUCTION
Trace, cut, and shape the wing ribs and fuselage bulkheads
from laminated balsa sheet. Using thin CA and a glass surface,
glue two sheets of 1/16 balsa, with the grain 90° to each other, to
create stock for the bulkheads.
As the plans indicate, there are plywood laminations on the nose ring
(1/64 inch), lower bulkheads #4 and #6 that face the wing, and center wing
LE (1/32 inch), and thumb-sized patches over the aft center portion of the
wing joint, to provide the structure with strength and durability.
Fuselage: The lower fuselage is built
upside-down over the plans, with the motor
mount submerged slightly into the building
board. Briefly soak the longerons in warm
water, to loosen them up to follow the plans
contour. Carefully pin the longerons to the
board over the plans.
Use a scrap 1/8 balsa stick to act as a
dummy tail post during fuselage
construction, but do not glue it in place. The
vertical stabilizer will eventually slide into
this gap.
Once dry, glue the bulkheads squarely
against the longerons, followed by the wing
crutch and lower longerons. The lower
longerons bend aggressively toward the
motor mount and must be preformed wet,
allowed to dry in place, and then glued. Use
epoxy for the motor mount and aliphatic
glue for the rest of the bulkheads.
Nose-side perimeters of bulkheads #2
and #3 and aft-facing perimeter #6 have thin
strips of soft 1/8 square balsa glued to them,
to provide increased adhesion area for balsa
planking.
Cover the upward-facing surface of the
battery floor with hook-and-loop fastener,
and glue it in place with epoxy. Once dry,
remove the lower fuselage from the board
and glue the upper bulkheads and dorsal
longeron in place.
The fuselage framework is spindly at this
point, so be careful as you use a long
sanding bar to gently bevel the bulkheads
and longerons to the fuselage’s curves,
leaving smooth, radiused surfaces to which
the planking will adhere.
Planking a fuselage takes time and effort,
but the end product is a work of art. Wear
gloves or barrier cream; you’ll get CA on
your skin during this process.
Employ a balsa stripper shimmed to
provide an approximate 60° angle on the
edge. Cut several dozen 7/16-inch-wide strips
from 1/16 balsa sheet.
Using thin CA and working from tail to
nose, glue the first strip midway over the
fuselage longeron. Carefully align the second
strip tightly and close to the first strip,
working slowly from tail to nose, stretching it
ever so slightly, placing it firmly against the
bulkheads. Apply microdrops of thin CA
every 1/2 inch or so, to glue the strips to each
other and to the bulkheads.
Apply two strips on the starboard side
and two strips on the port side, to prevent
warping the framework. Use the CA
sparingly, and occasionally go back from the
inside of the fuselage to glue loose planking,
and double-glue all strips to the bulkheads.
Continual strips can run on the sides from
the tail to the motor mount, using the watersoak/
prefitting trick to help shape the pieces
where necessary.
The planking strips will eventually be
unable to make the sharp, twisting bend
toward the motor mount. This is expected,
and the remaining open areas will be
planked on the top of the nose from
bulkhead #3 to the motor mount, and
eventually from the bottom of the nose from
bulkhead #4 to the motor mount. This
requires custom fitting, patience, a sanding
block, and trial and error, but it is highly
rewarding.
Plank the top of the nose starting at the
center and working out to the sides,
eventually custom-fitting strips to fill the
gaps. Wait to plank the lower nose and
lower aft fuselage until after you have
mounted the wing.
Five continual strips can be planked
down the center of the upper fuselage
between bulkhead #8 and bulkhead #3, but
eventually the compound curves become too
severe. The upper empennage is planked
with individually fitted pieces, and the
windshield edges are formed from triangleshaped
balsa-sheet inserts.
When you have completed the planking,
gently sand the high spots with 400-grit
paper to yield a smooth finish. Fill large
gaps with scrap balsa strips using sandable
aliphatic glue, and remedy imperfect
contours and small gaps with lightweight
spackling compound and more sanding. You
don’t want to sand too much, because the
sheeting is already relatively thin.
Size and shape the 1/32 plywood doublers
for the rudder and elevator to the servos you
intend to use, glue them onto the aft fuselage
as shown, and use a rotary tool to remove
the balsa sheet from the center of the cutout.
Make sure that the cutouts and servo screws
do not cut into the fuselage longerons.
I used Ernst pushrod exits as cooling
intakes on the lower nose and made an
appropriately sized cooling-air exit hole in
the ventral aft fuselage.
Mount the motor, propeller, and spinner
into the fuselage, and use 1/4 balsa sheet
with a 1/64-inch plywood lamination to
make an oversize nose ring. With the
plywood facing the spinner, sand the nose
ring to smoothly fair the fuselage to the
spinner. Cut a gap in the lower nose ring to
allow access to the propeller-adapter
setscrew.
Employ a light-plywood spacer to
position the aft wing mount, as plans show,
and bolt the mount to bulkhead #6, making
sure it is 1/8-1/4 inch below fuselage skin
level, to allow the wing TE to be flush with
the lower aft fuselage skins. Use scrap 1/32
plywood sheet on the aft side of bulkhead
#6 to form a strong base for the mount nuts
and washers.
Wing: The wing construction is
straightforward, using the dihedral gauge to
cant the top of each #1 rib out by 3°, giving
6° of final dihedral. The ribs must sit
squarely over the lower spar and the ventral
skegs must sit hard against the board, to
give the wing ribs proper angle and
washout. You will trim off the skegs before
you apply the lower sheeting.
Use diagonal braces to strengthen the
butt-joint corners where the LE and TE
meet ribs #1 and ribs #8. Add the small
balsa doublers to reinforce the hinge areas.
Minimally and gently smooth the ribs with
a sanding bar, and sheet the wing with 1/32
balsa. Add the wingtips made from soft
balsa blocks.
The aileron rods are fitted into grooves
cut into the unfinished wing’s TE, and then
the TE is fitted and glued in place. Position
the aileron servo off center, to preserve the
center ribs’ strength, and set it high on scrap
balsa/plywood pedestals to prevent the
servo screws from penetrating the wing spar
or the servo base from sticking through the
bottom of the wing. Attach the ailerons with
Robart 1/2A pin hinges, and seal the gap on
the top surface with strips of covering.
Sand the wing and ailerons gently and
minimally (remember that the wing skins
are thin), to obtain a smooth contour. Epoxy
the wing halves together using the main
spars as a guide for alignment. I used 1.5-
inch-long, 0.25-inch-wide strips of 1/32
plywood to laminate the upper and lower
spar joints.
Adhere the plywood doublers on the aft
wing joint, sand the centerline face of the
LE square, and epoxy the fuselage-wide 1/32
plywood sheet to the LE. Glue triangular
hard-balsa shims behind the LE plywood
facing, to add some structure to receive the
wing-mounting dowels.
Carefully sand the fuselage sides over
the wing crutch, to achieve a wing contour
with minimal gap between the top wing
surface and the fuselage side at the wing
crutch. Align the wing centerline joint with
the centers of the lower fuselage longerons.
Using the wing-mount hole as a guide,
mark, with a pencil lead, the wing-bolt
position from inside the fuselage. Drill the
appropriate hole through the wing, and bolt
the wing into the fuselage. Shim or grind
the mount as required to ensure that the
wing sits on the mounting bracket and is not
crushing the fuselage sides or wing surface.
Double-check the LE centerline with the
fuselage longeron and make sure that the
wing sits symmetrically in the saddle by
comparing it to a dummy horizontal
stabilizer that is temporarily glued across
the stern longerons.
Once you are satisfied with the
alignment, use an extra-long 1/8-inchdiameter
drill bit to bore the first hole
squarely through bulkhead #4 and into the
wing. Put a temporary dowel through hole
#1 to hold the wing in place, double-check
alignment, and drill hole #2.
Remove the wing and glue 1/8-inchdiameter
hardwood dowels into the holes.
Toughen the peg holes in bulkhead #4 with
thin CA, and then ream them clean.
Now you can plank the lower nose
fuselage and sheet the lower empennage
with cross-grain balsa. Build up the lower
wing fairing under the fuselage using a few
1/4-inch-wide by 1/16-inch-thick balsa strips
glued to the lower wing surface.
Sand these pieces flat before gluing a
cross-grain balsa filler on top of that.
Smoothly fair and/or fill the underside of
the wing into the lower fuselage.
Final Assembly: Cut the tail feathers from
1/8 balsa sheet using a 1/8-inch-square by 3-
inch-long hardwood stick or piano-wire
joiner to connect the elevator halves. I used
Granite State gapless iron-on hinge for the
elevator and rudder, with handmade 1/16
plywood horns epoxied into the moving
surfaces. The lower vertical stabilizer’s LE
slides into the groove in the aft end of the
fuselage.
The choice of power system and
batteries will dictate where you will mount
the batteries. There is plenty of room inside
the fuselage to mount the electrical
components, including elevator and rudder
servos, if desired.
For the prototype, the relatively heavy
cobalt motor, propeller, and spinner
mounted so far in front of the CG that it
necessitated placing the servos in the far
end of the tail, to avoid dreaded ballast.
Covering: We covered the prototype in
white and red MonoKote. The windows
were painted on with gray acrylic paint
outlined in black. Painting mistakes are
easy to remedy with a wipe of denatured
alcohol.
The turbine exhaust shrouds are handcarved
scrap balsa that was painted and
glued onto the fuselage with canopy glue.
Although the IV-P is a civil aircraft, the red
tail honors the Tuskegee Airmen.
Flying: With the CG and control throws set
per plans, with one click of up-elevator the
Lancair can be hand launched with a
moderate overhead throw at the horizon. It
powers out of the launch well and is
responsive in all axes.
The wing provides excellent inverted
and outside performance. The prototype
demonstrated a nice rate of speed, but a
modern brushless power system would
turn this airplane into a long-duration
screamer.
The propjet should be flown at a
shallow angle into a landing. You should
wait to attempt full-stall landings and lowlevel
aerobatics until you are accustomed
to the model’s performance envelope, wing
loading, and stall speed.
Even though the IV-P takes builder’s
skill and more time than some other
projects, the payoffs are an expansion of
your skill set and a sleek, distinctive, highperformance
airplane that is probably rare
to see at your airfield.
Gus Morfis
[email protected]
Tom Fey
[email protected]
MA Flies the Propjet: We were thrilled to
accept the Lancair project from Gus and
Tom. During the discussion, the need for
in-flight photos came up; the solution
offered was to ship the prototype to AMA
Headquarters. We accepted, of course.
We flew the model exactly as
described in the preceding and found the
performance reports to be spot on. We had
a blast flying the model with the brushedmotor
system and NiMH batteries. Call us
spoiled, but we couldn’t help but have
total confidence that a modern brushless
system and Li-Poly batteries would pump
this propjet even better into the sleek
speedster that its full-scale heritage
boasted.
Looking at what we had on hand, a sixpole,
2600 Kv inrunner helicopter motor
was exchanged for the Cobalt 400; it was
practically the same weight and size. The
ESC was exchanged for a brushless type
that included auto-detect programming
with Li-Poly cutoff protocols. We kept the
same 7 x 4 Master Airscrew propeller and
Du-Bro spinner.
The well-thought-out prototype flew
with the batteries right over the CG;
therefore, choosing the appropriate Li-Poly
was simply a matter of accommodating the
expected motor demand.
We settled on a 7.4-volt power source,
which tested on the bench to handle roughly
a 16-amp load. On hand was a 2400 mAh
10C Li-Poly battery that weighed roughly
half of the old 8.4-volt NiMH pack. We
dropped close to 2 ounces overall and
gained 50-65 watts of power. With smiles
all around, it was time to fly again.
The Lancair could be launched with
either an overhand or underhand toss. A
headwind actually helps a lot.
The extra power and lighter weight did
wonders for the friendly model. Pylon turns
were comfortable, as were any powerhungry
maneuver from level flight.
Shedding the bit of weight permitted a
landing that simulated a flop into the grass
rather than a skid.
Our final thoughts were that the Lancair
would suit any builder, no matter what power
choice was available; later changes are a
matter of plug-n-play. If a smooth runway is
at hand for you, the IV-P could be modified
for fixed (removable) landing gear. MA
Michael Ramsey
[email protected]
Sources:
Ernst Manufacturing
(503) 668-5597
www.ernstmfg.com
Robart
(630) 584-7616
www.robart.com
Master Airscrew/Windsor Propeller
(916) 631-8385
www.masterairscrew.com
Du-Bro
(800) 848-9411
www.dubro.com