I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price
Edition: Model Aviation - 2004/06
Page Numbers: 18,19,20,21,22,23,24,25,26,28,199
I’VE BEEN BUILDING model airplanes
of one kind or another for 60+ years and
writing for magazines for 27. This is the
76th published design from my drawing
board. In its way, the Cruiser 60 has been
the most pleasant surprise of all time.
Many of us fly our models in our minds
when they are on the drawing or building
board. Experience causes us to predict
fairly accurately what to expect from the
finished aircraft. The designs usually meet
those expectations. Those that are not up to
standard end up unpublished. Once in a
great while a design exceeds our
expectations, and even more rarely one
greatly exceeds our expectations. This
design does the latter.
After kicking the potential projects
around for a few weeks, I decided to
enlarge the previously published Cruiser
40 to 60 size since it would be attractive
and would photograph well for a cover. So
I enlarged it, built it, test-flew it a few
times, and made arrangements with Chris
Clark Studios to get my granddaughter
Marlena and the airplane in for photos.
Once all the photography was
completed, I began to fly the Cruiser more
and more aggressively. After several
hundred flights, what I anticipated would
be an average design has turned out to be
astonishing. I’ve changed some hardware
details and have moved the balance point
farther and farther aft.
My model balances 3⁄8 inch aft of the
point that was originally anticipated, and
that’s what I marked on the plans. That
makes the elevator and rudder responsive;
I’m using 100% exponential for them, but
it will initiate a spin or snap right now and
fortunately recover the same way each
time.
What started as a design that I
anticipated to be utilitarian has turned out
to be splendiferous through no genius on
my part—just blind dumb luck. If you have
the urge to “do it yourself” and build from
plans, this design is worthy of your
consideration.
The Model: This project is a follow-on to
a smaller version for .40-size power plants
that I developed which was published in
the September 1998 Flying Models. The
Cruiser 40 proved to be a delightful, fun
airplane that possessed remarkable speed
for its wing area.
I learned that the low-aspect-ratio wing
had distinct advantages, particularly for a
sport RC model. The Cruiser 40 had
remarkable speed yet gentle low-speed
characteristics. That disproportionate
speed envelope was directly connected to
the reduced aerodynamic drag at the
wing’s LE.
My aerodynamic engineering friends
have pointed out that most of a wing’s
drag is at the LE while the more aft
portions of the wing actually fly in a
vacuum (called lift). Steve Wittman
learned this decades ago and used the
phenomenon on numerous racers and
home-builts that he designed.
At model-aircraft speeds this decrease
in drag for a given amount of wing area is
of considerable benefit; we can have
models that are quick and aerobatic while
displaying above average low-speed
handling characteristics. It’s the best of
both worlds with few compromises.
Since I was so pleased with my 660-
18 MODEL AVIATION
Cruis6e0r by D. B. Mathews
Sport RC model features good looks and easy building:
an unbeatable combination
06sig1.QXD 3/25/04 9:38 am Page 18
square-inch 40-size version, I enlarged the model to
approximately 800 square inches and powered it with a .60
engine. The result is a model that retains the smaller version’s
virtues and features much improved visibility and smoother
flying, especially in moderate winds.
The Cruiser 60 is special in every way. It flies much faster
than a similarly powered model of equal wing area. Horizontal
and vertical performance are well out of proportion to its slowspeed
handling. It is a fully aerobatic design with trainerlike
landings and takeoffs. Not only that, but the thing is certainly
more attractive than many other midwing designs that are
currently flown.
The Cruiser 60’s fuselage is narrower than usual for two
reasons: a side-mounted engine’s muffler will easily clear the
fuselage without tedious structure removal and newer modern
servos and receivers simply do not require the fuselage width
formerly needed.
CONSTRUCTION
All hardware and material used in this project are standard
hobby-shop stock, or at least easy to order. The only special tools
needed are a jigsaw; a 12-inch-long, 1⁄4-inch-diameter drill bit;
and a carbide cutter in a hand grinder, but one could get by
without them.
The principle adhesive is medium cyanoacrylate; thin is used
for the hinges and epoxy is used for the wing joint and firewall
installation. Cover the Cruiser 60 wing with a high-heat Mylar
such as MonoKote or UltraCote; other materials may allow
excessive flex and twist.
The slot-in-tab light-plywood fuselage construction requires a
bit more work for the scratch builder, but it results in an easy-toassemble,
straight and true fuselage. The best way to make the
lightening cutouts is to drill 1⁄4-inch holes in a couple spots in
each cutout, threading the jigsaw blade through the holes and
cutting both fuselage sides out stacked.
Alternatively, the sides can be firm 1⁄8 balsa left unslotted aft
of the wing TE. In this instance I’d still use a light-plywood
(Poplar) doubler and assemble the fuselage by drawing a midline
on the up side of the top block and formers. The formers can be
adhered to the top exactly on the marks and truly vertical, and
then the sides can be pulled together against them.
Model designers have used the four-spar wing repeatedly,
which is a testament to its ease of construction, freedom from
warps, and lightness. The semisymmetrical airfoil will build flat
on the building board without the need for tabs or special fixtures.
There are several methods for transferring parts patterns to the
appropriate wood. My favorite is to make photocopies from the
plans, cut them slightly oversized, and adhere them to the wood
with a glue stick. You can then cut the parts, sand them to the
final outline, drill all holes, and then peel off the paper.
You can create large patterns, such as the fuselage sides, by
placing sheets of carbon paper between the plans and the sheet
wood. Use plastic-headed map pins to hold the three layers in
alignment. When you do this, use a straightedge for every line
possible and an adjustable french curve elsewhere; don’t try to
freehand anything you can draw with an edge.
Wing: Fabricate the ribs using the photocopy pattern technique.
Only two rib patterns are used in the wing. Pin this plywood
pattern onto a stack of rectangular balsa blanks and rough-cut
with a saw. Sand in the final outline. I like to cut the spar slots
undersized and then use a tool—made from spar scrap with
aluminum-oxide paper glued onto its bottom edge with
cyanoacrylate—to final-shape the slots.
You will need to trim the shear webs to match the rib spacing
June 2004 19
A “kit” of fuselage parts have been cut and drilled and readied
for use in the fuselage assembly.
Fuselage sides and formers are being assembled on fuselage top
block. Note use of weights, clamps, and squares.
The fuselage rear section, less cross-grain sheeting. Notice
pushrods cross over for straighter shots at horns.
Cross-grain sheeting is being applied. Masking tape “hinges” are
used to assemble segments flat on building board.
Photos courtesy the author
r
06sig1.QXD 3/25/04 9:40 am Page 19
20 MODEL AVIATION
Shown are the plywood rib patterns, nails used to hold the balsa
blank stack together, and sanding tools.
This is a view of the wing structure during construction. No
special fixture is required—just a flat bench.
This is how the aileron servo mounts to the rails in the wing. The
servo is mounted off-center. This worked fine!
Wing in fuselage saddle is drilled for hold-down dowels with
firewall removed. A 12-inch extension drill bit is handy here.
Engine on mount with spacer and ring taped to spinner
backplate. Intake and exhaust have been stuffed with paper.
The bare bones, uncovered airframe shows light yet sturdy
construction using well-proven techniques.
06sig1.QXD 3/25/04 9:42 am Page 20
by laying them over the drawings and
cutting off the excess. Score the centersection
ribs for later punch-out of the slot
into which the dihedral brace will be
inserted. I drill 1⁄16-inch holes, leaving
enough wood to hold things together.
Place waxed paper over the plans, and
position and pin the TE sheet, bottom
spars, and center-section sheeting, using
ribs to correctly position everything. Using
the shear webs and dihedral gauge,
position the ribs and adhere them. Add the
top spars and the upper center sheeting and
LE. Leave one part of the center-section
sheeting off until you have joined the
wings.
Repeat this process for the opposite
wing, remove and sand off any lumps or
bumps, and then carve the LE to the
outline shown on the plans.
Block up the outside tip of one wing
panel 3⁄4 inch, place the inboard end
parallel to a table edge, and use a coarse
sanding block to sand in the dihedral
angle. It may be necessary to saw off the
spar ends to match.
Repeat this process for the opposite
wing, and then trial-fit the center joint.
Some touch-up sanding may be needed to
obtain a nice, tight joint.
Punch out the previously scored center
rib slots and trial-fit the dihedral brace.
Trim and adjust to obtain a solid fit
between the wing halves with the dihedral
blocked in.
With one panel pinned flat and the
other blocked up to twice the dihedral,
smear epoxy (the long-cure type—not the
five-minute variety) onto both root ribs,
the slots, and the plywood gusset, and then
join and allow for curing. Install the last of
the center-section sheet.
You can develop wingtips from the two
cutoff rear ends of the fuselage top if they
were carefully trimmed off. Pin the scrap
in place and use a pencil to draw an outline
of the tip rib onto them. Remove the scrap,
cut oversize, and then sand to match the tip
rib and round the outside edges.
Cut the servo well and install the holddown
dowels after applying the fiberglass
tape. Cut the sections of sheet that will
contain the aileron servo horns. Slot them
at their faces with a knife, and then sand in
the slot using the threaded section of the
horns. Cut clearance holes for the vertical
portion of the horns. The horns exit the
bottom of the wing on this design and
should be as close together at the midline
as possible!
Position and adhere the center aileron
horn blocks to the wing TE using
cyanoacrylate glue. A bit of Vaseline
flowed between the wire and tube will
prevent them from getting stuck.
Sand the aileron blocks to match the
center-section. Fill the holes for the
vertical portion of the aileron horns with
modeling clay to prevent epoxy from
running into them when you are
fiberglassing the wing center-section.
My preference for this step is to use
Sonic-Tronics’ 6-inch-wide fiberglass
tape. Spray a precut length with 3M Spra-
Ment and then lay the tape on, starting in
the middle of the bottom. Pull and rub out
any wrinkles, and then brush thinned
epoxy through the weave. Don’t use more
epoxy than is required to fill the weave so
you don’t add excessive weight. Trowel
the epoxy into the fiberglass with a scrap
of wood until it all looks wetted.
After the epoxy has cured, measure and
mark a hole for the aileron servo. I’ve been
mounting the servo off-center to avoid
cutting into the center ribs. I have done
this on my last three projects and am
unable to tell any difference in flight.
Cut through the epoxy/fiberglass and
the underlying balsa to create a hole that
will just clear the servo and its wires.
Measure another set of cutouts for 3⁄8 x 3⁄8-
inch basswood strips. These should extend
through the center ribs and outboard at
least a half inch. You can make this cutout
with a knife, but a carbide cutter in a hand
grinder is certainly speedier. The servo
rails should sit flush with the balsa/epoxy
surface. You can adhere them with
cyanoacrylate.
Trial-fit the aileron servo and its
hardware, and cut off the excess horn
below the connectors for clearance of the
fuselage servos. Create two overlength
sections of 3⁄8 balsa for the ailerons. Mark
a midline on the rear, and carve them to an
airfoil shape using a razor plane and
sandpaper blocks. Cut off enough for the
fixed portion at the tips, and adhere to the
TE with cyanoacrylate. Trim the remainder
to fit, with roughly 1⁄8 inch clearance on
both ends.
Sand in the usual hinge-line bevel, and
then slot the aileron and drill for the horns
per the instructions for the elevator. Trialfit
and adjust the hot hinges.
Fuselage: Using the previously mentioned
carbon-paper transfer system, develop a
fuselage side, a doubler, and the formers.
Nail another section of wood under the
first, and cut out the sides and doublers in
pairs. Sand all edges flush with each other.
Be sure to mark one as left and the other as
right.
Join the doubler to the side with
troweled epoxy (the five-minute variety is
okay here). Weight these left and right
sides while the epoxy is curing. Check the
fit of all formers in slots; they should fit
snugly but not require force to seat.
Mark a full-length midline on the top
block and on the formers. Nail down the
top block, and then position the formers to
match the midline.
Do not cut the upper wing-saddle pan
loose from the fuselage sides until the
fuselage construction is nearly finished.
Use masking tape and clamps to
preassemble the fuselage, and then check
for squareness in all planes. Position the
center-section over the top block, and then
flow medium cyanoacrylate along the
joints. The landing-gear block and its
June 2004 21
Here you can easily see the spinner/cowl joint, the removable
tank hatch, and the engine and muffler.
With wing hatch and wing removed, you can see the lower
fuselage area. Receiver, servos, and battery reside here.
06sig1.QXD 3/25/04 9:43 am Page 21
triangular braces should be installed with epoxy. Do not adhere
the firewall permanently until the wing has been trial-fit and the
dowel holes have been drilled!
Draw the tail post and its filler together over the midline mark,
and then add the rear formers, maintaining squareness and
alignment at all times. Some weight will help in this step. When
you are satisfied, adhere everything with cyanoacrylate.
As an aid in later sanding and shaping, place a scrap of 3⁄8 balsa
in the aft portion of the elevator slot and in the rudder slot using a
drop or two of cyanoacrylate. The 3⁄8-inch triangular stock top
corner fillers can easily be cut to the proper length using the
bottom former spaces as a cutting guide. Then they are adhered to
the corners.
In the past I’ve had major problems trying to bend a full-length
section and adding the formers with triangular cutouts. I can never
get the triangular stock to lay flat when it is also bent.
Adhere the tail-wheel bracket piece, and then cover the bottom
rear with cross-grain balsa. I prefer hinging the sections flat on a
building board with masking tape, flowing cyanoacrylate onto the
edges, and then installing the unit onto the fuselage bottom. The
forward section is covered with cross-grain light plywood joined
with the balsa over a scrap of 3⁄8 balsa strip. Again, do not adhere
it to the firewall.
Rough-cut the bottom sheeting to an approximate match to the
fuselage side. Using an X-Acto #26 blade or a sharp knife, roughcut
the fuselage top block. Be conservative here; some of that 3⁄8
sheet scrap can be used for the tail feathers.
Remove the fuselage from the building board, and sand the top
and bottom to a rough outline fit at this time. You will contour
everything after assembly. See the cross-section view on the
plans.
Cut the wing-saddle hatch loose. Mark cut lines on the top
block and the sides, and then cut through them with a razor saw.
Add interior formers and sand for a smooth, sliding fit between
the removable hatch and the fuselage formers. Allow enough
space for the covering material. Cut into the previously prepared
slots in the various formers, and add the basswood hold-down
blocks. Epoxy the wing hold-down and its triangular
reinforcements to the fuselage side.
For a neat joint between the wing and the hatch, pencil-mark
any area that may be holding the hatch off and trim this area using
a shoemaker’s file. A shoemaker’s file has medium and coarse
textures and a flat and curved side.
The top of this hatch must be level with the other parts of the
fuselage top. It is held to the model with 4-40 bolts into threaded
holes in basswood blocks. Notice that the blocks are offset from
the middle front and back; this allows room for the canopy. The
landing-gear strap hold-downs have held up with no problems
during all the flying. I also adhere short sections of scrap
basswood to the wing top that are arranged to prevent the hatch
from moving from side to side.
Position the wing in the saddle, making sure it is centered.
Using a string running from the center of the tail post to the
wingtips, adjust the wing in its saddle until the tip-to-center
distance is equal. Holding the wing steady in the saddle with a
weight is helpful. Drill and tap the wing hold-down for the bolts.
Remove the firewall and drill 1⁄4-inch holes through the
predrilled holes in F-2, into the center-section joint, all the way
through the dihedral brace. A 12-inch-long bit is useful here, but a
normal 3-inch-long unit will at least mark the hole entry on the
wing. In that case, drill the rest of the hole freehand with the wing
removed.
Sharpen the dowels on the inside end with a pencil sharpener.
Spread epoxy inside the hole with a scrap of wire, coat the dowels,
and insert them into the wing, point first. Hold the wing in the
fuselage with the nylon bolts while the epoxy cures. You can also
permanently epoxy the firewall and its braces at this time.
Install the tank hatch block, drilling into it from the front for the
1⁄8-inch dowel that will be glued into it. Also drill 1⁄8 inch through the
block and into the underlying hardwood mount. The hold-down bolt
runs into the mount and a blind nut. Attach the hatch with its dowel
and bolt, and then cut and sand it to match the fuselage sides.
22 MODEL AVIATION
Cruiser 60
The wing hatch is held in place with landing-gear straps and
bolts. The pilot figure is Ace 1⁄4-scale Cap’n Ed.
The wing hatch has been removed to show bass blocks adhered
to the wing top to prevent shifting.
TYPE: RC sport
WINGSPAN: 61 inches
ENGINE: .60
FLYING WEIGHT: 6 pounds, 10 ounces
CONSTRUCTION: Balsa, light plywood, plywood
COVERING/FINISH: Heat-shrink film of choice
06sig1.QXD 3/25/04 9:44 am Page 22
June 2004 23
06sig1.QXD 3/25/04 9:45 am Page 23
Full-Size Plans Available—see page 199
24 MODEL AVIATION
06sig1.QXD 3/25/04 9:45 am Page 24
Cowl: Screw the engine to its mount, tackglue
a filler to hold the nose ring onto the
engine, and then tack-glue the ring to the
back of the spinner.
Use the fuselage side view to rough-cut a
3⁄8-inch block for the cowl side. Measure the
difference between the front and rear using
the top view, block up one end that amount,
and, using the table-edge technique, sand in
the appropriate bevel. Turn the block over
and sand the other bevel the same way.
Check for a good fit between the block
and the firewall and spinner ring. Go slowly,
sanding a little at a time until they join nicely,
and then cut the top and bottom of the block
the same way. Once they all fit and leave
some room for shaping, adhere the whole
assembly in place with cyanoacrylate. You
may need to fill the corners on the front with
scraps of 3⁄8-inch triangular stock to reinforce
them.
Remove the engine, then carve the blocks
to a pleasant shape that is flush with the
firewall and spinner ring. This step will go
faster if you use that #26 X-Acto blade or
sharp knife for rough shaping. Follow that
with 100-grit sandpaper, and work your way
down to 220 grit. This process is not as
tedious as it sounds; take your time and
remember that the sanding block is just as
much a cutting instrument as a knife is. After
you have shaped the cowl, fill the interior
joints with epoxy.
Sand everything into a smooth blend
from the front to the rear. Do this with the
wing saddle installed with 4-40 bolts into the
threaded blocks and the tank hatch installed.
Fill holes and dings with one of the
microballoon fillers, and then fine-sand the
entire unit with 400-grit sandpaper.
Tail: These are straightforward sheet
surfaces. However, if the engine system to
be used weighs less than 25 ounces
complete, you may want to lighten the tail
by using a sandwich construction for the
stabilizer. To do that, make a 1⁄4-inch-strip
interior covered top and bottom with 1⁄16
balsa. Otherwise, use medium C-grain sheet.
The model tends to be slightly nose-heavy
with most .60-size engines, so the needed
tail weight might as well be in the structure.
The forward part of the fin has the grain
running horizontal for added strength. This
part does not sit in the fuselage top slot
either. Join sheet sections on a flat surface.
The elevator joiner wire is easier to get right
if it is installed before the elevator halves
are cut apart. It is also helpful to drill the
horn holes slightly oversized and fill the
gaps with the epoxy.
Sand the perimeters of these structures
round at the LE and with an airfoil-type
taper toward the rear. Hinge lines are
beveled. Trial-fit the hinges before final
sanding.
Covering and Finish: The curve of the fin,
stabilizer, and wingtips are easier to cover if
you seal a strip of covering material that is
approximately 1⁄2 inch wide on the perimeters
before applying the major sections. This is
also true for the ends of the ailerons and their
matching cutouts at the wing TE.
Seat these strips along the midline, and
then pull them out and down while applying
heat, trying for as much coverage, without
wrinkles, as possible. Trim off the wrinkled
areas, then proceed using the manufacturer’s
recommended technique.
Cover the parts separately and then
assemble them. The covering material will go
further if you cover the largest sections first.
I much prefer to seal the hinge lines. This
greatly improves the control surfaces’
efficiency, improving handling and
responsiveness while greatly reducing the
potential for flutter. My pet method is to
adhere the covering along the LE, stretch it,
and seal it to the rear of the fixed surface,
adhere it to the tips, and cut through the
covering for the joint between the edges that
will move and those that don’t.
Deflect the movable surface away from
the covering, then tack it along the face edge
of the hinge line. Stretch the plastic out to the
TE and seal. Seal the other borders, and run a
trim iron along the hinge line again with the
surface deflected. Repeat for the opposite
side of the panel, and then use a heat gun to
06sig1.QXD 3/25/04 9:46 am Page 26
shrink everything tight. Try to avoid
overdoing the heat on the hinge lines.
The net result is sealed surfaces that are
relatively easy to develop yet extremely
effective. They will reduce the required
throws for any given maneuver by roughly
half compared to open hinge lines.
I covered the model in the photos with
Bright Yellow UltraCote, painted the wheel
pants with Rust-Oleum, and the graphics are
Sig A&B vinyl stick-ons. I left the metal gear
natural and polished it to a mirror finish with
Happich Semichrome. (Available at
motorcycle shops.) I painted the Du-Bro gear
with Rust-Oleum.
Last Details: I prefer Sullivan tail-wheel
brackets, but I could not find one locally. The
Sig aluminum gear fits nicely but is a bit
short on propeller clearance when the model
is flying from long grass. The Du-Bro
fiberglass-filled Super Strength Landing Gear
(part number 789) does provide an extra inch
of ground clearance.
Fuel-proof the interior of the engine and
tank compartments with two coats of thinned
epoxy. Smear some of the excess into the
forward areas of the radio compartment just
in case. The model looks nice if the interior
of the engine room is painted; I used K&B
Ultrapoxy. It is best to do these steps after the
model is covered.
The low-rate control-surface deflections
specified on the plans will provide nicely
controlled loops and rolls, but they are
insufficient for violent snaps, etc. However,
in high rate, hang on!
I prefer solid wire in tube connections for
the control hookups. I use Sullivan Solid
Steel Rod Type Golden Rods (part number
S511) 2-56 threaded rods with a solder link
on the servo end and a threaded clevis on the
surface end. These are run through pushrod
guides as shown on the drawings, trying for
as close to a straight shot as possible. The
rudder rod is attached to the outside of the
left servo, the elevator to the right side of the
center servo, and the throttle cable to the
outside of the right servo.
You will need to trim the canopy.
Remove all but approximately 1⁄8 inch of the
horizontal flash with canopy scissors. Place
the canopy on a flat surface, and score the
outline using a tool made from a #11 X-Acto
blade cyanoacrylate glued between two
layers of 1⁄16 scrap plywood. Hold the tool flat
against the work surface, and gently move it
around the canopy’s perimeter. Use canopy
scissors on the sharp curves fore and aft, and
crack and peel the rest.
Adhere the canopy to the hatch by
marking its outline and then removing
roughly 3⁄32 inch of the covering to match.
Attach the canopy with Wilhold RC/56
canopy glue, and use trim tape to hide the
joint.
By placing the battery pack under the
tank, the receiver on the floor, and the servos
well down in the fuselage rear (but with
working room forward of the wing mount),
my prototypes are coming out a tad noseheavy.
If you somehow create a model that
hangs tail-low when two fingers are placed at
the marked balance point, add nose weight.
Do not attempt to fly this model tail-heavy!
In the Air: The Cruiser 60 is attractive for a
midwing design, somewhat resembling a fullscale
Goodyear racer, but appearance is only
skin deep. Beneath that sharp-looking
exterior lies a surprising model. Its low
aspect ratio and comparatively thin airfoil
produce a model with an astounding speed
range. In low throttle it behaves much like an
aileron trainer, producing well-controlled
slow landings, gentle “down the pipe”
takeoffs, and no vices when flown slowly.
Turn on the juice, and wow! The Cruiser
60 moves like smoke. Aerobatics are limited
only by the flier’s skills. The model will roll
from one end of the field to the other and do
rolling circles, wild-looking horizontal and
vertical snap rolls, spin flat, do lovely vertical
8s and vertical Cuban 8s, and knife edge with
little coupling, all in a controlled manner.
This model does not “jump and flit”; it
flies like an airplane! Not only that, but it
looks good. So build yourself one and fly it
for fun. MA
D.B. Mathews
909 N. Maize Rd. Townhouse 734
Wichita KS 67212
28 MODEL AVIATION
MA Pllans Serviice
now online!
The Plans Service on the AMA Web site
now offers pictures of nearly every
model aircraft featured in Model Aviation
construction articles since 1975!
You can see what a model looks like
before purchasing the plans, and
then download the construction article
from the MA Digital Archives.
Remember that the Digital Archives
is a members-only benefit.
www.modelaircraft.org/templates/ama/plans.asp
06sig1.QXD 3/25/04 9:48 am Page 28
F u l l - S i z e P l a n s
958 Patriot ...........................................................................................................$11.25
CL Classic Stunt model by Phelps spans 57.5 inches
959 Cruiser 60 ...................................................................................................$22.50
D.B. Mathews’ RC sport model is follow-up to 40-size design
No. 917 Sir Lancelot: RC sport model by Henry for O.S. .61 spans 72 inches D
No. 918 Skyraider: CL 1/2A Profile by Sarpolus for Norvel BigMig .061 spans 29 inches B
No. 925 Bird-E-Dog: Ernie Heyworth and Ed Lokken’s RC Electric Sport Scale model C
No. 926 JoeCat: RC sport jet by Beshar for Toki .18 DF unit spans 37 inches C
No. 927 Kairos: CL Stunt model by Dixon for .46-.61 engine spans 58 inches C
No. 928 Beta Blue Chip Racer: Rubber-powered FF Scale model designed by Tom Derber B
No. 929 Dewoitine D.338: Multimotor RC Electric Scale by Mikulasko spans 781/2 inches E
No. 930 Westland Lysander: RC Scale model by Baker for .25 spans 56 inches E
No. 931 1959 Ares: Champion RC Aerobatics model by Werwage spans 501/2 inches C
No. 932 Wing400: RC Electric flying wing by Hanley for Speed 400 spans 36 inches B
No. 933 Kepler 450: CL speed-limit Combat model by Edwards for .21-.32 two-stroke A
Plan does not include full-size template shown on page 40 of the August 2002 issue.
No. 934 VariEze: FF Peanut Scale canard by Heckman spans 13 inches A
No. 935 Classic 320: 1/2A Classic Power design by Pailet for Cyclon .049 or equivalent B
No. 936 Prince: RC sport Pattern model by Robelen for O.S. .25 spans 51 inches C
No. 937 Clean Cut: RC sport aerobatic model by Sarpolus spans 90 inches E
No. 938 Diamond Gem: Compressed-air-powered FF sport model by Ken Johnson B
No. 939 Project Extra: RC Scale Aerobatics model by Mike Hurley spans 106 inches **$49.50
No. 940 Cessna No.1: RC Electric Sport Scale by Papic spans 321/2 inches B
No. 941 Mooney and Beechcraft Bonanza CL 1/2A profile sport models by Rick Sarpolus B
No. 942 Zenith CH 801: FF Rubber Scale model by Fineman spans 20 inches A
No. 943 Wildman 60: Old-Time Ignition CL Stunt model by Carter spans 591/2 inches C
No. 944 Shoestring: Semiscale RC sport Pattern design by deBolt spans 60 inches D
No. 945 F-86 Sabre: Semiscale CL Stunt model by Hutchinson spans 56 inches E
No. 946 Electric Zephyr: Electric RC Pylon/sport model by Smith spans 40 inches B
No. 947 Chester Special: O.S. .40-powered CL Scale model by Beatty spans 43 inches **$27.00
No. 948 Moffett Redux: High-performance Rubber-powered FF design by Langenberg C
No. 949 Scratch-One: Electric RC sailplane/basic trainer by Aberle spans 45 inches B
No. 950 BareCat 650-C: CL sport Stunt model by Netzeband spans 541/4 inches E
No. 951 Douglas O-46A: RC Sport Scale model by Baker spans 54 inches E
No. 952 Lavochkin LaGG-3: Felton’s CL Sport Scale design made from cardboard E
No. 953 USA-1: Multiple-award-winning CL Stunt model by Werwage spans 611/2 inches C
No. 954 B-2 Spirit Stealth Bomber: Electric FF model by Ken Johnson spans 42 inches B
No. 955 Electric Flash: Electric-powered RC park flyer by Stewart spans 44 inches C
No. 956 Grumman F-4F Wildcat: Jim Ryan’s RC Electric fighter spans 30.6 inches C
No. 957 Right Angle: RC sport aerobatic model by Sarpolus spans 62 inches D
Full-size plan list available. A complete listing of all plans previously published in this
magazine through no. 959 may be obtained free of charge by writing (enclose 78¢
stamped, pre-addressed #10 business-size letter envelope) Model Aviation, 5161 E.
Memorial Dr., Muncie IN 47302
**Special Price