Nothing flies quite like one - 2010/08

IF THERE IS one aircraft that has come to represent all of the early
lightplanes, it has to be the Piper Cub. Designed in 1937, the J-3 Cub
was essentially an upgrade of the J-2, and it underwent a number of
changes and improvements throughout the years.
August 2010 31
J-3 Cub
countless military and civilian pilots. It has
also provided many hours of enjoyment
flying low and slow, watching the scenery
slip by slowly.
It has been said that “the Cub is a great
airplane as long as you don’t have anywhere
to go.” Having spent many hours in the
“family Cub” as a kid, I say it’s a great
airplane whether you have a place to go or
not.
The Model: If there is one aircraft that has
been “overmodeled,” it has to be the Piper
Cub. This is because it’s a terrific and
recognizable design that flies well. I’ve built
or flown several models of J-3s and Super
Cubs, ranging in wingspan from 12 feet to
36 inches and weighing between 36 pounds
and 51/2 ounces, and I’ve loved them all.
A few years ago I discovered that for
park flying, 40-inch-span lightplanes were
the perfect size and weight for GWS IPS
power and flew beautifully as three-channel
models, but they were also well suited for
four channels. And a collection of scale
models is incomplete without the venerable
old J-3.
I designed the 40-inch Cub to be
configured as either a three- or four-channel
model by simply building the wing of
choice. And since the wings plug into the
fuselage, the design can be constructed both
ways merely by fabricating a second set of
wings.
Construction is primarily of balsa. The stickand-
tissue building style makes for a nice scale
appearance and provides a strong yet
lightweight airframe that is flown with
economical power to provide scalelike flying
qualities.
The design features a functional cabin door,
for easy battery access. To help keep the
airframe light and sturdy, the wingtip and tailsection
outlines and cabin D windows are
bowed from laminated balsa.
CONSTRUCTION
Begin by bowing the laminated outlines.
Make the bowing patterns from 3/16-inch-thick
artist’s foam board using the templates provided.
The Cub handles nicely with aileron wings and slideslips beautifully.
Pat’s models are so lightweight that
room for the burden of scale detail—
such as bungee covers and fuel tank
indicator float—is available.
Type: RC Scale park flyer
Skill level: Intermediate builder, novice pilot
Wingspan: 40 inches
Wing area: 230 square inches
Length: 25.5 inches
Weight: 7.2-8.0 ounces
Wing loading: 4.5-5.0 ounces/square foot
Power: Maxx Products International EPU-4 motor, GWS 8 x 6 propeller, 430 mAh
2S Li-Poly battery
Radio: Three to four channels with 3- to 6-amp ESC, two to four micro (4 gram)
servos
Construction: All balsa (laser-cut short kit is available)
Finish shown: Solite iron-on covering (or use equivalent in weight)
Flight duration: 15-20 minutes
Soak some medium-firm wood in water
for an hour or so, to soften it. With the balsa
pulled around the form and glued, you can
put the wood in the microwave for 12-14
seconds to accelerate the drying process.
The “Sources” list at the end of the
article contains a Web site address for a
detailed how-to on bowing outlines.
Tail Sections: With bows made, cut all the
parts using the patterns provided to make
print wood or obtain a laser-cut parts pack
from Pat’s Custom Models.
32 MODEL AVIATION
The rudder and horizontal stabilizer are
built over the plans, using wood sizes
shown. Pin the shaped parts and frame the
assemblies around them. When dry, remove
the parts from the board and sand to shape.
Make hinges from 1/8-inch-wide strips of
thin CA hinge stock, but don’t glue them in
until after the frames are covered.
Bend the tail wheel strut to shape from
.032-inch wire, using the provided pattern.
Fit it into the rudder as shown and glue in
place.
Wing: Before beginning wing construction,
decide whether you will build the threechannel,
the aileron version, or both. Plans
and parts are provided for both assemblies,
so keep a close eye on the part numbers used
for your choice.
Since the wing panels plug in, dihedral is
set up by the two root ribs. Pay close
attention as you select the components.
For the three-channel wing, pin parts A2
and A3 in place over the associated wing
plans. Dry-fit ribs R2, R3, and R4 onto main
spar A1. Pin the 1/16 x 1/4 TE over the plans,
followed by the rib/spar assembly, and glue
in place.
Fit and glue in place the R1 ribs, 3/16 x 3/8
balsa LE, and tip bow. Cut the 5/32-inch-OD
aluminum socket tubes to length and glue
them into the wing at R1 and R2, and then
adhere the the 1/16 square balsa top spars.
When dry, remove the wing panels from
the board and sand to shape.
Begin the aileron wing by pinning A2A
and A3A in place over the plans. Build up
the aileron spar assemblies using the detail
drawing provided. Be sure to make a lefthand
and a right-hand assembly.
Bring together ribs R2A, R3A, R3B, and
R4A onto main spar AA1. Pin the 1/16 x 1/4
TE over the plans. Then attach the rib/spar
assembly and aileron spar assembly AS1,
and glue in place.
Fit and glue the R1 ribs and the 3/16 x 3/8
balsa LE in place. Do the same with the tip
bow. Cut the 5/32-inch-OD aluminum socket
tubes to length and glue them into the wing
at R1 and R2A, and then cut and install the
1/16 square balsa top spars.
Sand a bevel into aileron hinge spar AS2
using the R3B rib detail drawing as a
reference. Glue aileron ribs AR and ARA in
place on AS2, and then glue the assembly in
place on the TE.
When dry, remove the wing from the
board and sand to shape. Cut the aileron
from the wing and sand it to final shape, and
then fit and adhere AHM in place flush with
the bottom of the aileron assembly. Cut the
hinges 5/32 inch wide and fit them in the
aileron, but don’t glue them in until after the
frames are covered.
Fit and glue SM1 and SM2 servo mount
gussets in place on A2A. Neutral the servo
and, with the output arm screwed in place,
bond it to the mount with silicone adhesive.
Fuselage: Constructing this section begins
with side frames. Because the side door
opens, the right and left frames are different,
so separate framing plans are provided for
each.
Build both frames over the plans using
wood sizes shown. Pin B1L and B1R in
place and frame the sides around it. Locate
and glue B2 to the inside of each frame.
Adhere B3 flush with the outside edge of the
right-hand side frame.
When dry, remove the frames from the
board. Make the landing gear beams from 1/8
x 3/16 balsa. Gouge appropriate-size slots in
the front and rear beams, and pin them in
place over the top-view drawing.
Using triangles or machinist’s squares to
ensure vertical alignment, glue the fuselage
sides in place on landing gear beams;
remember that the door is on the right-hand
side. Assemble former 2/2A and glue it in
place along with cabin formers 3, 4, 5, and
6. Adhere the B4 ribs between formers 3 and
4.
Sand the bevel into the fuselage sides at
the tail end. Using the triangles or squares,
pull the tail post together and glue. Fit and
adhere formers 7, 8, 9, 10, and 11 in place
on top of the fuselage. When dry, remove
the frame from the board and add all 1/16 x
1/8 balsa bottom crosspieces.
Glue former 1 in place flush with the
front of the fuselage frame. Notice the
orientation of the motor-mount-stick hole in
the detail drawing; it is offset to
accommodate motor right thrust.
Build up the motor mount and glue it in
place to the firewall. Using the remaining
cross-sectional drawings, add balsa stringers
and cabin outfill, and sand to shape.
Fitting Wing Struts: Build wing lift struts
over the plans using wood sizes shown. Two
patterns are provided, since the three- and
four-channel wing dihedral angles are
different. Cut the struts a bit overlength on
the outboard end, to be trimmed to fit later.
Bend the .032-inch-diameter wire retention
clips to shape, and adhere the bottom clip in
place on the struts.
Cut six pieces of 1/16-inch-OD aluminum
tube 5/16 inch long. Use thread to lash the
strut retention tubes in place on the fuselage
and wings, and secure with thin CA. Cut 1/8-
inch-OD aluminum dowel to 81/2 inches
long to make the wing mounting pins, and
slip them into the fuselage.
Slide the wing panels onto the dowels,
and fit the struts into the tube sockets on the
fuselage. Trim the front strut to length, and
then set up the outer fittings and glue them
into the struts.
Twist approximately 1° of washout into
the wing panels. The amount of washout
isn’t as critical as both sides being the same.
Trim the rear struts and fit the retention clips
into the strut, and glue.
Be careful not to accidentally glue the
retention clips into the tubes, or you will be
unable to remove the strut from the wing.
Bend the jury struts to shape using the
appropriate pattern. Slip the strut into the
holes in A2/A2A, align vertically, use thread
to lash them to the lift strut, and secure with
thin CA.
August 2010 35
Add the 1/16 x 1/8 balsa strut fairings to
the jury struts to complete the process.
Landing Gear: Employing the patterns
provided, bend the landing gear components
to shape from the appropriate wire sizes. Lay
out the front strut and solder together using
Stay-Brite silver solder. Tape the front and
rear struts to the fuselage and solder.
Remove the landing gear assembly from
the fuselage and wash it with soap and water
to prevent corrosion. Now use thread to bind
the landing gear assembly to the beams, and
secure with thin CA. Add the 1/8 scrap balsa
gussets and 1/16 balsa fill.
Use the patterns provided to make the boot
cowl sections from yellow file-folder material,
and adhere them in place with white glue.
Start with the bottom, go to the sides, and then
bond the top.
To complete the fuselage assembly, build
the upper and lower cabin side doors directly
over the plans, from the wood sizes shown.
Sand to shape.
Mounting Servos and Motor: Glue servo
mount rails and beams in the fuselage. Space
the rails to fit your specific unit.
Screw the servos in place and run in the
elevator pushrod tube (Sullivan item 507),
supported at both ends and in a couple of
places in the middle using standoffs made
from short sections of the included pushrod
sheathing. The pushrod will be made from
.025-inch-diameter wire.
Fit the rudder and elevator into the
fuselage, and run in the rudder pull-pull cables
using the routing diagram on the plans. Tie
the cables off on the toothpick control horn
and note the exact location where the cable
will exit the covering. Mark that location on
the plans.
Set up the motor and ESC, and test the
system for proper rotation. Fit the motor onto
the mount stick and secure it with a dab of
silicone adhesive.
Now is a good time to assemble the model
and double-check for problems that might
arise. If an issue crops up, fix it now, while
things are still easy to access.
Covering: You can cover the Cub with tissue,
light silkspan and dope, or iron-on covering.
The best choice for iron-on is Coverite
Airspan or Litespan, if you like the dopedtissue
look. A good Mylar is Coverite
Microlite, also sold as Nelson Hobby
Specialties’ LiteFilm and So-Lite. Whatever
you choose, follow the manufacturer’s
instructions for best results.
I don’t recommend iron-on materials such
as MonoKote or UltraCote; their excessive
shrinking qualities will damage the light
structure, and the excessive weight will
adversely affect the model’s flying qualities.
Begin by covering all frames except the
vertical fin and fuselage top. With the frames
covered, plug in the wings and fit the
horizontal stabilizer in the fuselage, align
using the wings for reference, and adhere in
place.
Align and glue in place the vertical fin.
Cover the top of the fuselage and vertical fin
using a separate piece of covering for the leftand
right-hand sides, to form the fillet at the
base of the fin.
The side door is hinged to the fuselage
using hinge tape or covering material. Add
trim as desired. Callie Graphics has the trim
scheme for my model. Callie can also provide
custom graphics for any desired scheme.
Final Assembly: You can carve the cowl and
dummy engine from blue foam or balsa, or a
vacuum-formed cowl is supplied in the
previously mentioned parts pack. Fit the cowl
to the fuselage and screw it in place with
small sheet-metal screws.
Seal struts with a couple coats of waterbased
varnish or dope. Paint them with Model
Master Acryl.
Glue hinges in place in the rudder and
elevator, and fit them onto the model using
Pacer Formula 560 Canopy Glue or
equivalent. Run in the elevator pushrod, Zbend
the back end, and, with the elevator in
neutral position, glue the control horn in
place.
Mark exit points for rudder cables on the
fuselage. Reinforce the covering with tape or
vinyl trim stock, and pierce the covering at the
exit points. Run the rudder cables into the
fuselage and tie the cables to the control horn.
Drill the holes in the vertical fin and
horizontal stabilizer, and run in the tail-brace
rigging using light Kevlar thread. Adhere the
aileron hinges in place.
Make aileron pushrods from .032-inchdiameter
wire, with Z-bends on both ends. Fit
the rods onto the servo and control horn,
align the aileron to neutral, and glue the horn
in place.
Use brass tubes to size the holes in the
wheels down to 3/32-inch ID. Fit the 3/32-inch-
OD tubing to the axles and epoxy in place.
Mount the wheels using Du-Bro E/Z
Connector plastic keepers on both sides of
each. Fit and glue the side windows and
windshield using .005-.008 acetate. Add
remaining details you desire to finish the J-3.
With it basically ready to fly, set the CG
as shown on the plans, using battery and
receiver locations to your best advantage.
Mount the components on 1/16 hard-balsa
plates, using Velcro to secure them in place.
Set up controls as the plans show, and
you’re ready to go.
Flying: The three-channel Cub is easy to fly
but is slightly sensitive to windy conditions,
so it’s best to test-fly on a calm day.
Before the first flight, double-check the
control throws and ensure that they are
moving in the right direction. It’s no fun to
learn that one (or more) of the controls is
backward after liftoff.
The model should trim for straight and
level flight at approximately two-thirds
power. The controls are positive but not
overly sensitive.
The same rules apply to the four-channel
version, but on takeoff the rudder is
controlled with the left hand. Typical of the
Cub, the ailerons will induce a bit of adverse
yaw, so a bit of rudder is needed to
coordinate the turns.
Rudder can also be mixed with aileron
input, but doing that will make sideslipping
much more difficult. The Cub is a lot of fun
and wonderful at sideslipping. Differential
throw can also be mixed into the ailerons, to
help eliminate adverse yaw.
Otherwise, the little J-3 flies wonderfully.
It handles well and slows nicely for terrific
touch-and-gos.
This airplane will also do nice scale loops

IF THERE IS one aircraft that has come to represent all of the early
lightplanes, it has to be the Piper Cub. Designed in 1937, the J-3 Cub
was essentially an upgrade of the J-2, and it underwent a number of
changes and improvements throughout the years.
August 2010 31
J-3 Cub
countless military and civilian pilots. It has
also provided many hours of enjoyment
flying low and slow, watching the scenery
slip by slowly.
It has been said that “the Cub is a great
airplane as long as you don’t have anywhere
to go.” Having spent many hours in the
“family Cub” as a kid, I say it’s a great
airplane whether you have a place to go or
not.
The Model: If there is one aircraft that has
been “overmodeled,” it has to be the Piper
Cub. This is because it’s a terrific and
recognizable design that flies well. I’ve built
or flown several models of J-3s and Super
Cubs, ranging in wingspan from 12 feet to
36 inches and weighing between 36 pounds
and 51/2 ounces, and I’ve loved them all.
A few years ago I discovered that for
park flying, 40-inch-span lightplanes were
the perfect size and weight for GWS IPS
power and flew beautifully as three-channel
models, but they were also well suited for
four channels. And a collection of scale
models is incomplete without the venerable
old J-3.
I designed the 40-inch Cub to be
configured as either a three- or four-channel
model by simply building the wing of
choice. And since the wings plug into the
fuselage, the design can be constructed both
ways merely by fabricating a second set of
wings.
Construction is primarily of balsa. The stickand-
tissue building style makes for a nice scale
appearance and provides a strong yet
lightweight airframe that is flown with
economical power to provide scalelike flying
qualities.
The design features a functional cabin door,
for easy battery access. To help keep the
airframe light and sturdy, the wingtip and tailsection
outlines and cabin D windows are
bowed from laminated balsa.
CONSTRUCTION
Begin by bowing the laminated outlines.
Make the bowing patterns from 3/16-inch-thick
artist’s foam board using the templates provided.
The Cub handles nicely with aileron wings and slideslips beautifully.
Pat’s models are so lightweight that
room for the burden of scale detail—
such as bungee covers and fuel tank
indicator float—is available.
Type: RC Scale park flyer
Skill level: Intermediate builder, novice pilot
Wingspan: 40 inches
Wing area: 230 square inches
Length: 25.5 inches
Weight: 7.2-8.0 ounces
Wing loading: 4.5-5.0 ounces/square foot
Power: Maxx Products International EPU-4 motor, GWS 8 x 6 propeller, 430 mAh
2S Li-Poly battery
Radio: Three to four channels with 3- to 6-amp ESC, two to four micro (4 gram)
servos
Construction: All balsa (laser-cut short kit is available)
Finish shown: Solite iron-on covering (or use equivalent in weight)
Flight duration: 15-20 minutes
Soak some medium-firm wood in water
for an hour or so, to soften it. With the balsa
pulled around the form and glued, you can
put the wood in the microwave for 12-14
seconds to accelerate the drying process.
The “Sources” list at the end of the
article contains a Web site address for a
detailed how-to on bowing outlines.
Tail Sections: With bows made, cut all the
parts using the patterns provided to make
print wood or obtain a laser-cut parts pack
from Pat’s Custom Models.
32 MODEL AVIATION
The rudder and horizontal stabilizer are
built over the plans, using wood sizes
shown. Pin the shaped parts and frame the
assemblies around them. When dry, remove
the parts from the board and sand to shape.
Make hinges from 1/8-inch-wide strips of
thin CA hinge stock, but don’t glue them in
until after the frames are covered.
Bend the tail wheel strut to shape from
.032-inch wire, using the provided pattern.
Fit it into the rudder as shown and glue in
place.
Wing: Before beginning wing construction,
decide whether you will build the threechannel,
the aileron version, or both. Plans
and parts are provided for both assemblies,
so keep a close eye on the part numbers used
for your choice.
Since the wing panels plug in, dihedral is
set up by the two root ribs. Pay close
attention as you select the components.
For the three-channel wing, pin parts A2
and A3 in place over the associated wing
plans. Dry-fit ribs R2, R3, and R4 onto main
spar A1. Pin the 1/16 x 1/4 TE over the plans,
followed by the rib/spar assembly, and glue
in place.
Fit and glue in place the R1 ribs, 3/16 x 3/8
balsa LE, and tip bow. Cut the 5/32-inch-OD
aluminum socket tubes to length and glue
them into the wing at R1 and R2, and then
adhere the the 1/16 square balsa top spars.
When dry, remove the wing panels from
the board and sand to shape.
Begin the aileron wing by pinning A2A
and A3A in place over the plans. Build up
the aileron spar assemblies using the detail
drawing provided. Be sure to make a lefthand
and a right-hand assembly.
Bring together ribs R2A, R3A, R3B, and
R4A onto main spar AA1. Pin the 1/16 x 1/4
TE over the plans. Then attach the rib/spar
assembly and aileron spar assembly AS1,
and glue in place.
Fit and glue the R1 ribs and the 3/16 x 3/8
balsa LE in place. Do the same with the tip
bow. Cut the 5/32-inch-OD aluminum socket
tubes to length and glue them into the wing
at R1 and R2A, and then cut and install the
1/16 square balsa top spars.
Sand a bevel into aileron hinge spar AS2
using the R3B rib detail drawing as a
reference. Glue aileron ribs AR and ARA in
place on AS2, and then glue the assembly in
place on the TE.
When dry, remove the wing from the
board and sand to shape. Cut the aileron
from the wing and sand it to final shape, and
then fit and adhere AHM in place flush with
the bottom of the aileron assembly. Cut the
hinges 5/32 inch wide and fit them in the
aileron, but don’t glue them in until after the
frames are covered.
Fit and glue SM1 and SM2 servo mount
gussets in place on A2A. Neutral the servo
and, with the output arm screwed in place,
bond it to the mount with silicone adhesive.
Fuselage: Constructing this section begins
with side frames. Because the side door
opens, the right and left frames are different,
so separate framing plans are provided for
each.
Build both frames over the plans using
wood sizes shown. Pin B1L and B1R in
place and frame the sides around it. Locate
and glue B2 to the inside of each frame.
Adhere B3 flush with the outside edge of the
right-hand side frame.
When dry, remove the frames from the
board. Make the landing gear beams from 1/8
x 3/16 balsa. Gouge appropriate-size slots in
the front and rear beams, and pin them in
place over the top-view drawing.
Using triangles or machinist’s squares to
ensure vertical alignment, glue the fuselage
sides in place on landing gear beams;
remember that the door is on the right-hand
side. Assemble former 2/2A and glue it in
place along with cabin formers 3, 4, 5, and
6. Adhere the B4 ribs between formers 3 and
4.
Sand the bevel into the fuselage sides at
the tail end. Using the triangles or squares,
pull the tail post together and glue. Fit and
adhere formers 7, 8, 9, 10, and 11 in place
on top of the fuselage. When dry, remove
the frame from the board and add all 1/16 x
1/8 balsa bottom crosspieces.
Glue former 1 in place flush with the
front of the fuselage frame. Notice the
orientation of the motor-mount-stick hole in
the detail drawing; it is offset to
accommodate motor right thrust.
Build up the motor mount and glue it in
place to the firewall. Using the remaining
cross-sectional drawings, add balsa stringers
and cabin outfill, and sand to shape.
Fitting Wing Struts: Build wing lift struts
over the plans using wood sizes shown. Two
patterns are provided, since the three- and
four-channel wing dihedral angles are
different. Cut the struts a bit overlength on
the outboard end, to be trimmed to fit later.
Bend the .032-inch-diameter wire retention
clips to shape, and adhere the bottom clip in
place on the struts.
Cut six pieces of 1/16-inch-OD aluminum
tube 5/16 inch long. Use thread to lash the
strut retention tubes in place on the fuselage
and wings, and secure with thin CA. Cut 1/8-
inch-OD aluminum dowel to 81/2 inches
long to make the wing mounting pins, and
slip them into the fuselage.
Slide the wing panels onto the dowels,
and fit the struts into the tube sockets on the
fuselage. Trim the front strut to length, and
then set up the outer fittings and glue them
into the struts.
Twist approximately 1° of washout into
the wing panels. The amount of washout
isn’t as critical as both sides being the same.
Trim the rear struts and fit the retention clips
into the strut, and glue.
Be careful not to accidentally glue the
retention clips into the tubes, or you will be
unable to remove the strut from the wing.
Bend the jury struts to shape using the
appropriate pattern. Slip the strut into the
holes in A2/A2A, align vertically, use thread
to lash them to the lift strut, and secure with
thin CA.
August 2010 35
Add the 1/16 x 1/8 balsa strut fairings to
the jury struts to complete the process.
Landing Gear: Employing the patterns
provided, bend the landing gear components
to shape from the appropriate wire sizes. Lay
out the front strut and solder together using
Stay-Brite silver solder. Tape the front and
rear struts to the fuselage and solder.
Remove the landing gear assembly from
the fuselage and wash it with soap and water
to prevent corrosion. Now use thread to bind
the landing gear assembly to the beams, and
secure with thin CA. Add the 1/8 scrap balsa
gussets and 1/16 balsa fill.
Use the patterns provided to make the boot
cowl sections from yellow file-folder material,
and adhere them in place with white glue.
Start with the bottom, go to the sides, and then
bond the top.
To complete the fuselage assembly, build
the upper and lower cabin side doors directly
over the plans, from the wood sizes shown.
Sand to shape.
Mounting Servos and Motor: Glue servo
mount rails and beams in the fuselage. Space
the rails to fit your specific unit.
Screw the servos in place and run in the
elevator pushrod tube (Sullivan item 507),
supported at both ends and in a couple of
places in the middle using standoffs made
from short sections of the included pushrod
sheathing. The pushrod will be made from
.025-inch-diameter wire.
Fit the rudder and elevator into the
fuselage, and run in the rudder pull-pull cables
using the routing diagram on the plans. Tie
the cables off on the toothpick control horn
and note the exact location where the cable
will exit the covering. Mark that location on
the plans.
Set up the motor and ESC, and test the
system for proper rotation. Fit the motor onto
the mount stick and secure it with a dab of
silicone adhesive.
Now is a good time to assemble the model
and double-check for problems that might
arise. If an issue crops up, fix it now, while
things are still easy to access.
Covering: You can cover the Cub with tissue,
light silkspan and dope, or iron-on covering.
The best choice for iron-on is Coverite
Airspan or Litespan, if you like the dopedtissue
look. A good Mylar is Coverite
Microlite, also sold as Nelson Hobby
Specialties’ LiteFilm and So-Lite. Whatever
you choose, follow the manufacturer’s
instructions for best results.
I don’t recommend iron-on materials such
as MonoKote or UltraCote; their excessive
shrinking qualities will damage the light
structure, and the excessive weight will
adversely affect the model’s flying qualities.
Begin by covering all frames except the
vertical fin and fuselage top. With the frames
covered, plug in the wings and fit the
horizontal stabilizer in the fuselage, align
using the wings for reference, and adhere in
place.
Align and glue in place the vertical fin.
Cover the top of the fuselage and vertical fin
using a separate piece of covering for the leftand
right-hand sides, to form the fillet at the
base of the fin.
The side door is hinged to the fuselage
using hinge tape or covering material. Add
trim as desired. Callie Graphics has the trim
scheme for my model. Callie can also provide
custom graphics for any desired scheme.
Final Assembly: You can carve the cowl and
dummy engine from blue foam or balsa, or a
vacuum-formed cowl is supplied in the
previously mentioned parts pack. Fit the cowl
to the fuselage and screw it in place with
small sheet-metal screws.
Seal struts with a couple coats of waterbased
varnish or dope. Paint them with Model
Master Acryl.
Glue hinges in place in the rudder and
elevator, and fit them onto the model using
Pacer Formula 560 Canopy Glue or
equivalent. Run in the elevator pushrod, Zbend
the back end, and, with the elevator in
neutral position, glue the control horn in
place.
Mark exit points for rudder cables on the
fuselage. Reinforce the covering with tape or
vinyl trim stock, and pierce the covering at the
exit points. Run the rudder cables into the
fuselage and tie the cables to the control horn.
Drill the holes in the vertical fin and
horizontal stabilizer, and run in the tail-brace
rigging using light Kevlar thread. Adhere the
aileron hinges in place.
Make aileron pushrods from .032-inchdiameter
wire, with Z-bends on both ends. Fit
the rods onto the servo and control horn,
align the aileron to neutral, and glue the horn
in place.
Use brass tubes to size the holes in the
wheels down to 3/32-inch ID. Fit the 3/32-inch-
OD tubing to the axles and epoxy in place.
Mount the wheels using Du-Bro E/Z
Connector plastic keepers on both sides of
each. Fit and glue the side windows and
windshield using .005-.008 acetate. Add
remaining details you desire to finish the J-3.
With it basically ready to fly, set the CG
as shown on the plans, using battery and
receiver locations to your best advantage.
Mount the components on 1/16 hard-balsa
plates, using Velcro to secure them in place.
Set up controls as the plans show, and
you’re ready to go.
Flying: The three-channel Cub is easy to fly
but is slightly sensitive to windy conditions,
so it’s best to test-fly on a calm day.
Before the first flight, double-check the
control throws and ensure that they are
moving in the right direction. It’s no fun to
learn that one (or more) of the controls is
backward after liftoff.
The model should trim for straight and
level flight at approximately two-thirds
power. The controls are positive but not
overly sensitive.
The same rules apply to the four-channel
version, but on takeoff the rudder is
controlled with the left hand. Typical of the
Cub, the ailerons will induce a bit of adverse
yaw, so a bit of rudder is needed to
coordinate the turns.
Rudder can also be mixed with aileron
input, but doing that will make sideslipping
much more difficult. The Cub is a lot of fun
and wonderful at sideslipping. Differential
throw can also be mixed into the ailerons, to
help eliminate adverse yaw.
Otherwise, the little J-3 flies wonderfully.
It handles well and slows nicely for terrific
touch-and-gos.
This airplane will also do nice scale loops

IF THERE IS one aircraft that has come to represent all of the early
lightplanes, it has to be the Piper Cub. Designed in 1937, the J-3 Cub
was essentially an upgrade of the J-2, and it underwent a number of
changes and improvements throughout the years.
August 2010 31
J-3 Cub
countless military and civilian pilots. It has
also provided many hours of enjoyment
flying low and slow, watching the scenery
slip by slowly.
It has been said that “the Cub is a great
airplane as long as you don’t have anywhere
to go.” Having spent many hours in the
“family Cub” as a kid, I say it’s a great
airplane whether you have a place to go or
not.
The Model: If there is one aircraft that has
been “overmodeled,” it has to be the Piper
Cub. This is because it’s a terrific and
recognizable design that flies well. I’ve built
or flown several models of J-3s and Super
Cubs, ranging in wingspan from 12 feet to
36 inches and weighing between 36 pounds
and 51/2 ounces, and I’ve loved them all.
A few years ago I discovered that for
park flying, 40-inch-span lightplanes were
the perfect size and weight for GWS IPS
power and flew beautifully as three-channel
models, but they were also well suited for
four channels. And a collection of scale
models is incomplete without the venerable
old J-3.
I designed the 40-inch Cub to be
configured as either a three- or four-channel
model by simply building the wing of
choice. And since the wings plug into the
fuselage, the design can be constructed both
ways merely by fabricating a second set of
wings.
Construction is primarily of balsa. The stickand-
tissue building style makes for a nice scale
appearance and provides a strong yet
lightweight airframe that is flown with
economical power to provide scalelike flying
qualities.
The design features a functional cabin door,
for easy battery access. To help keep the
airframe light and sturdy, the wingtip and tailsection
outlines and cabin D windows are
bowed from laminated balsa.
CONSTRUCTION
Begin by bowing the laminated outlines.
Make the bowing patterns from 3/16-inch-thick
artist’s foam board using the templates provided.
The Cub handles nicely with aileron wings and slideslips beautifully.
Pat’s models are so lightweight that
room for the burden of scale detail—
such as bungee covers and fuel tank
indicator float—is available.
Type: RC Scale park flyer
Skill level: Intermediate builder, novice pilot
Wingspan: 40 inches
Wing area: 230 square inches
Length: 25.5 inches
Weight: 7.2-8.0 ounces
Wing loading: 4.5-5.0 ounces/square foot
Power: Maxx Products International EPU-4 motor, GWS 8 x 6 propeller, 430 mAh
2S Li-Poly battery
Radio: Three to four channels with 3- to 6-amp ESC, two to four micro (4 gram)
servos
Construction: All balsa (laser-cut short kit is available)
Finish shown: Solite iron-on covering (or use equivalent in weight)
Flight duration: 15-20 minutes
Soak some medium-firm wood in water
for an hour or so, to soften it. With the balsa
pulled around the form and glued, you can
put the wood in the microwave for 12-14
seconds to accelerate the drying process.
The “Sources” list at the end of the
article contains a Web site address for a
detailed how-to on bowing outlines.
Tail Sections: With bows made, cut all the
parts using the patterns provided to make
print wood or obtain a laser-cut parts pack
from Pat’s Custom Models.
32 MODEL AVIATION
The rudder and horizontal stabilizer are
built over the plans, using wood sizes
shown. Pin the shaped parts and frame the
assemblies around them. When dry, remove
the parts from the board and sand to shape.
Make hinges from 1/8-inch-wide strips of
thin CA hinge stock, but don’t glue them in
until after the frames are covered.
Bend the tail wheel strut to shape from
.032-inch wire, using the provided pattern.
Fit it into the rudder as shown and glue in
place.
Wing: Before beginning wing construction,
decide whether you will build the threechannel,
the aileron version, or both. Plans
and parts are provided for both assemblies,
so keep a close eye on the part numbers used
for your choice.
Since the wing panels plug in, dihedral is
set up by the two root ribs. Pay close
attention as you select the components.
For the three-channel wing, pin parts A2
and A3 in place over the associated wing
plans. Dry-fit ribs R2, R3, and R4 onto main
spar A1. Pin the 1/16 x 1/4 TE over the plans,
followed by the rib/spar assembly, and glue
in place.
Fit and glue in place the R1 ribs, 3/16 x 3/8
balsa LE, and tip bow. Cut the 5/32-inch-OD
aluminum socket tubes to length and glue
them into the wing at R1 and R2, and then
adhere the the 1/16 square balsa top spars.
When dry, remove the wing panels from
the board and sand to shape.
Begin the aileron wing by pinning A2A
and A3A in place over the plans. Build up
the aileron spar assemblies using the detail
drawing provided. Be sure to make a lefthand
and a right-hand assembly.
Bring together ribs R2A, R3A, R3B, and
R4A onto main spar AA1. Pin the 1/16 x 1/4
TE over the plans. Then attach the rib/spar
assembly and aileron spar assembly AS1,
and glue in place.
Fit and glue the R1 ribs and the 3/16 x 3/8
balsa LE in place. Do the same with the tip
bow. Cut the 5/32-inch-OD aluminum socket
tubes to length and glue them into the wing
at R1 and R2A, and then cut and install the
1/16 square balsa top spars.
Sand a bevel into aileron hinge spar AS2
using the R3B rib detail drawing as a
reference. Glue aileron ribs AR and ARA in
place on AS2, and then glue the assembly in
place on the TE.
When dry, remove the wing from the
board and sand to shape. Cut the aileron
from the wing and sand it to final shape, and
then fit and adhere AHM in place flush with
the bottom of the aileron assembly. Cut the
hinges 5/32 inch wide and fit them in the
aileron, but don’t glue them in until after the
frames are covered.
Fit and glue SM1 and SM2 servo mount
gussets in place on A2A. Neutral the servo
and, with the output arm screwed in place,
bond it to the mount with silicone adhesive.
Fuselage: Constructing this section begins
with side frames. Because the side door
opens, the right and left frames are different,
so separate framing plans are provided for
each.
Build both frames over the plans using
wood sizes shown. Pin B1L and B1R in
place and frame the sides around it. Locate
and glue B2 to the inside of each frame.
Adhere B3 flush with the outside edge of the
right-hand side frame.
When dry, remove the frames from the
board. Make the landing gear beams from 1/8
x 3/16 balsa. Gouge appropriate-size slots in
the front and rear beams, and pin them in
place over the top-view drawing.
Using triangles or machinist’s squares to
ensure vertical alignment, glue the fuselage
sides in place on landing gear beams;
remember that the door is on the right-hand
side. Assemble former 2/2A and glue it in
place along with cabin formers 3, 4, 5, and
6. Adhere the B4 ribs between formers 3 and
4.
Sand the bevel into the fuselage sides at
the tail end. Using the triangles or squares,
pull the tail post together and glue. Fit and
adhere formers 7, 8, 9, 10, and 11 in place
on top of the fuselage. When dry, remove
the frame from the board and add all 1/16 x
1/8 balsa bottom crosspieces.
Glue former 1 in place flush with the
front of the fuselage frame. Notice the
orientation of the motor-mount-stick hole in
the detail drawing; it is offset to
accommodate motor right thrust.
Build up the motor mount and glue it in
place to the firewall. Using the remaining
cross-sectional drawings, add balsa stringers
and cabin outfill, and sand to shape.
Fitting Wing Struts: Build wing lift struts
over the plans using wood sizes shown. Two
patterns are provided, since the three- and
four-channel wing dihedral angles are
different. Cut the struts a bit overlength on
the outboard end, to be trimmed to fit later.
Bend the .032-inch-diameter wire retention
clips to shape, and adhere the bottom clip in
place on the struts.
Cut six pieces of 1/16-inch-OD aluminum
tube 5/16 inch long. Use thread to lash the
strut retention tubes in place on the fuselage
and wings, and secure with thin CA. Cut 1/8-
inch-OD aluminum dowel to 81/2 inches
long to make the wing mounting pins, and
slip them into the fuselage.
Slide the wing panels onto the dowels,
and fit the struts into the tube sockets on the
fuselage. Trim the front strut to length, and
then set up the outer fittings and glue them
into the struts.
Twist approximately 1° of washout into
the wing panels. The amount of washout
isn’t as critical as both sides being the same.
Trim the rear struts and fit the retention clips
into the strut, and glue.
Be careful not to accidentally glue the
retention clips into the tubes, or you will be
unable to remove the strut from the wing.
Bend the jury struts to shape using the
appropriate pattern. Slip the strut into the
holes in A2/A2A, align vertically, use thread
to lash them to the lift strut, and secure with
thin CA.
August 2010 35
Add the 1/16 x 1/8 balsa strut fairings to
the jury struts to complete the process.
Landing Gear: Employing the patterns
provided, bend the landing gear components
to shape from the appropriate wire sizes. Lay
out the front strut and solder together using
Stay-Brite silver solder. Tape the front and
rear struts to the fuselage and solder.
Remove the landing gear assembly from
the fuselage and wash it with soap and water
to prevent corrosion. Now use thread to bind
the landing gear assembly to the beams, and
secure with thin CA. Add the 1/8 scrap balsa
gussets and 1/16 balsa fill.
Use the patterns provided to make the boot
cowl sections from yellow file-folder material,
and adhere them in place with white glue.
Start with the bottom, go to the sides, and then
bond the top.
To complete the fuselage assembly, build
the upper and lower cabin side doors directly
over the plans, from the wood sizes shown.
Sand to shape.
Mounting Servos and Motor: Glue servo
mount rails and beams in the fuselage. Space
the rails to fit your specific unit.
Screw the servos in place and run in the
elevator pushrod tube (Sullivan item 507),
supported at both ends and in a couple of
places in the middle using standoffs made
from short sections of the included pushrod
sheathing. The pushrod will be made from
.025-inch-diameter wire.
Fit the rudder and elevator into the
fuselage, and run in the rudder pull-pull cables
using the routing diagram on the plans. Tie
the cables off on the toothpick control horn
and note the exact location where the cable
will exit the covering. Mark that location on
the plans.
Set up the motor and ESC, and test the
system for proper rotation. Fit the motor onto
the mount stick and secure it with a dab of
silicone adhesive.
Now is a good time to assemble the model
and double-check for problems that might
arise. If an issue crops up, fix it now, while
things are still easy to access.
Covering: You can cover the Cub with tissue,
light silkspan and dope, or iron-on covering.
The best choice for iron-on is Coverite
Airspan or Litespan, if you like the dopedtissue
look. A good Mylar is Coverite
Microlite, also sold as Nelson Hobby
Specialties’ LiteFilm and So-Lite. Whatever
you choose, follow the manufacturer’s
instructions for best results.
I don’t recommend iron-on materials such
as MonoKote or UltraCote; their excessive
shrinking qualities will damage the light
structure, and the excessive weight will
adversely affect the model’s flying qualities.
Begin by covering all frames except the
vertical fin and fuselage top. With the frames
covered, plug in the wings and fit the
horizontal stabilizer in the fuselage, align
using the wings for reference, and adhere in
place.
Align and glue in place the vertical fin.
Cover the top of the fuselage and vertical fin
using a separate piece of covering for the leftand
right-hand sides, to form the fillet at the
base of the fin.
The side door is hinged to the fuselage
using hinge tape or covering material. Add
trim as desired. Callie Graphics has the trim
scheme for my model. Callie can also provide
custom graphics for any desired scheme.
Final Assembly: You can carve the cowl and
dummy engine from blue foam or balsa, or a
vacuum-formed cowl is supplied in the
previously mentioned parts pack. Fit the cowl
to the fuselage and screw it in place with
small sheet-metal screws.
Seal struts with a couple coats of waterbased
varnish or dope. Paint them with Model
Master Acryl.
Glue hinges in place in the rudder and
elevator, and fit them onto the model using
Pacer Formula 560 Canopy Glue or
equivalent. Run in the elevator pushrod, Zbend
the back end, and, with the elevator in
neutral position, glue the control horn in
place.
Mark exit points for rudder cables on the
fuselage. Reinforce the covering with tape or
vinyl trim stock, and pierce the covering at the
exit points. Run the rudder cables into the
fuselage and tie the cables to the control horn.
Drill the holes in the vertical fin and
horizontal stabilizer, and run in the tail-brace
rigging using light Kevlar thread. Adhere the
aileron hinges in place.
Make aileron pushrods from .032-inchdiameter
wire, with Z-bends on both ends. Fit
the rods onto the servo and control horn,
align the aileron to neutral, and glue the horn
in place.
Use brass tubes to size the holes in the
wheels down to 3/32-inch ID. Fit the 3/32-inch-
OD tubing to the axles and epoxy in place.
Mount the wheels using Du-Bro E/Z
Connector plastic keepers on both sides of
each. Fit and glue the side windows and
windshield using .005-.008 acetate. Add
remaining details you desire to finish the J-3.
With it basically ready to fly, set the CG
as shown on the plans, using battery and
receiver locations to your best advantage.
Mount the components on 1/16 hard-balsa
plates, using Velcro to secure them in place.
Set up controls as the plans show, and
you’re ready to go.
Flying: The three-channel Cub is easy to fly
but is slightly sensitive to windy conditions,
so it’s best to test-fly on a calm day.
Before the first flight, double-check the
control throws and ensure that they are
moving in the right direction. It’s no fun to
learn that one (or more) of the controls is
backward after liftoff.
The model should trim for straight and
level flight at approximately two-thirds
power. The controls are positive but not
overly sensitive.
The same rules apply to the four-channel
version, but on takeoff the rudder is
controlled with the left hand. Typical of the
Cub, the ailerons will induce a bit of adverse
yaw, so a bit of rudder is needed to
coordinate the turns.
Rudder can also be mixed with aileron
input, but doing that will make sideslipping
much more difficult. The Cub is a lot of fun
and wonderful at sideslipping. Differential
throw can also be mixed into the ailerons, to
help eliminate adverse yaw.
Otherwise, the little J-3 flies wonderfully.
It handles well and slows nicely for terrific
touch-and-gos.
This airplane will also do nice scale loops

IF THERE IS one aircraft that has come to represent all of the early
lightplanes, it has to be the Piper Cub. Designed in 1937, the J-3 Cub
was essentially an upgrade of the J-2, and it underwent a number of
changes and improvements throughout the years.
August 2010 31
J-3 Cub
countless military and civilian pilots. It has
also provided many hours of enjoyment
flying low and slow, watching the scenery
slip by slowly.
It has been said that “the Cub is a great
airplane as long as you don’t have anywhere
to go.” Having spent many hours in the
“family Cub” as a kid, I say it’s a great
airplane whether you have a place to go or
not.
The Model: If there is one aircraft that has
been “overmodeled,” it has to be the Piper
Cub. This is because it’s a terrific and
recognizable design that flies well. I’ve built
or flown several models of J-3s and Super
Cubs, ranging in wingspan from 12 feet to
36 inches and weighing between 36 pounds
and 51/2 ounces, and I’ve loved them all.
A few years ago I discovered that for
park flying, 40-inch-span lightplanes were
the perfect size and weight for GWS IPS
power and flew beautifully as three-channel
models, but they were also well suited for
four channels. And a collection of scale
models is incomplete without the venerable
old J-3.
I designed the 40-inch Cub to be
configured as either a three- or four-channel
model by simply building the wing of
choice. And since the wings plug into the
fuselage, the design can be constructed both
ways merely by fabricating a second set of
wings.
Construction is primarily of balsa. The stickand-
tissue building style makes for a nice scale
appearance and provides a strong yet
lightweight airframe that is flown with
economical power to provide scalelike flying
qualities.
The design features a functional cabin door,
for easy battery access. To help keep the
airframe light and sturdy, the wingtip and tailsection
outlines and cabin D windows are
bowed from laminated balsa.
CONSTRUCTION
Begin by bowing the laminated outlines.
Make the bowing patterns from 3/16-inch-thick
artist’s foam board using the templates provided.
The Cub handles nicely with aileron wings and slideslips beautifully.
Pat’s models are so lightweight that
room for the burden of scale detail—
such as bungee covers and fuel tank
indicator float—is available.
Type: RC Scale park flyer
Skill level: Intermediate builder, novice pilot
Wingspan: 40 inches
Wing area: 230 square inches
Length: 25.5 inches
Weight: 7.2-8.0 ounces
Wing loading: 4.5-5.0 ounces/square foot
Power: Maxx Products International EPU-4 motor, GWS 8 x 6 propeller, 430 mAh
2S Li-Poly battery
Radio: Three to four channels with 3- to 6-amp ESC, two to four micro (4 gram)
servos
Construction: All balsa (laser-cut short kit is available)
Finish shown: Solite iron-on covering (or use equivalent in weight)
Flight duration: 15-20 minutes
Soak some medium-firm wood in water
for an hour or so, to soften it. With the balsa
pulled around the form and glued, you can
put the wood in the microwave for 12-14
seconds to accelerate the drying process.
The “Sources” list at the end of the
article contains a Web site address for a
detailed how-to on bowing outlines.
Tail Sections: With bows made, cut all the
parts using the patterns provided to make
print wood or obtain a laser-cut parts pack
from Pat’s Custom Models.
32 MODEL AVIATION
The rudder and horizontal stabilizer are
built over the plans, using wood sizes
shown. Pin the shaped parts and frame the
assemblies around them. When dry, remove
the parts from the board and sand to shape.
Make hinges from 1/8-inch-wide strips of
thin CA hinge stock, but don’t glue them in
until after the frames are covered.
Bend the tail wheel strut to shape from
.032-inch wire, using the provided pattern.
Fit it into the rudder as shown and glue in
place.
Wing: Before beginning wing construction,
decide whether you will build the threechannel,
the aileron version, or both. Plans
and parts are provided for both assemblies,
so keep a close eye on the part numbers used
for your choice.
Since the wing panels plug in, dihedral is
set up by the two root ribs. Pay close
attention as you select the components.
For the three-channel wing, pin parts A2
and A3 in place over the associated wing
plans. Dry-fit ribs R2, R3, and R4 onto main
spar A1. Pin the 1/16 x 1/4 TE over the plans,
followed by the rib/spar assembly, and glue
in place.
Fit and glue in place the R1 ribs, 3/16 x 3/8
balsa LE, and tip bow. Cut the 5/32-inch-OD
aluminum socket tubes to length and glue
them into the wing at R1 and R2, and then
adhere the the 1/16 square balsa top spars.
When dry, remove the wing panels from
the board and sand to shape.
Begin the aileron wing by pinning A2A
and A3A in place over the plans. Build up
the aileron spar assemblies using the detail
drawing provided. Be sure to make a lefthand
and a right-hand assembly.
Bring together ribs R2A, R3A, R3B, and
R4A onto main spar AA1. Pin the 1/16 x 1/4
TE over the plans. Then attach the rib/spar
assembly and aileron spar assembly AS1,
and glue in place.
Fit and glue the R1 ribs and the 3/16 x 3/8
balsa LE in place. Do the same with the tip
bow. Cut the 5/32-inch-OD aluminum socket
tubes to length and glue them into the wing
at R1 and R2A, and then cut and install the
1/16 square balsa top spars.
Sand a bevel into aileron hinge spar AS2
using the R3B rib detail drawing as a
reference. Glue aileron ribs AR and ARA in
place on AS2, and then glue the assembly in
place on the TE.
When dry, remove the wing from the
board and sand to shape. Cut the aileron
from the wing and sand it to final shape, and
then fit and adhere AHM in place flush with
the bottom of the aileron assembly. Cut the
hinges 5/32 inch wide and fit them in the
aileron, but don’t glue them in until after the
frames are covered.
Fit and glue SM1 and SM2 servo mount
gussets in place on A2A. Neutral the servo
and, with the output arm screwed in place,
bond it to the mount with silicone adhesive.
Fuselage: Constructing this section begins
with side frames. Because the side door
opens, the right and left frames are different,
so separate framing plans are provided for
each.
Build both frames over the plans using
wood sizes shown. Pin B1L and B1R in
place and frame the sides around it. Locate
and glue B2 to the inside of each frame.
Adhere B3 flush with the outside edge of the
right-hand side frame.
When dry, remove the frames from the
board. Make the landing gear beams from 1/8
x 3/16 balsa. Gouge appropriate-size slots in
the front and rear beams, and pin them in
place over the top-view drawing.
Using triangles or machinist’s squares to
ensure vertical alignment, glue the fuselage
sides in place on landing gear beams;
remember that the door is on the right-hand
side. Assemble former 2/2A and glue it in
place along with cabin formers 3, 4, 5, and
6. Adhere the B4 ribs between formers 3 and
4.
Sand the bevel into the fuselage sides at
the tail end. Using the triangles or squares,
pull the tail post together and glue. Fit and
adhere formers 7, 8, 9, 10, and 11 in place
on top of the fuselage. When dry, remove
the frame from the board and add all 1/16 x
1/8 balsa bottom crosspieces.
Glue former 1 in place flush with the
front of the fuselage frame. Notice the
orientation of the motor-mount-stick hole in
the detail drawing; it is offset to
accommodate motor right thrust.
Build up the motor mount and glue it in
place to the firewall. Using the remaining
cross-sectional drawings, add balsa stringers
and cabin outfill, and sand to shape.
Fitting Wing Struts: Build wing lift struts
over the plans using wood sizes shown. Two
patterns are provided, since the three- and
four-channel wing dihedral angles are
different. Cut the struts a bit overlength on
the outboard end, to be trimmed to fit later.
Bend the .032-inch-diameter wire retention
clips to shape, and adhere the bottom clip in
place on the struts.
Cut six pieces of 1/16-inch-OD aluminum
tube 5/16 inch long. Use thread to lash the
strut retention tubes in place on the fuselage
and wings, and secure with thin CA. Cut 1/8-
inch-OD aluminum dowel to 81/2 inches
long to make the wing mounting pins, and
slip them into the fuselage.
Slide the wing panels onto the dowels,
and fit the struts into the tube sockets on the
fuselage. Trim the front strut to length, and
then set up the outer fittings and glue them
into the struts.
Twist approximately 1° of washout into
the wing panels. The amount of washout
isn’t as critical as both sides being the same.
Trim the rear struts and fit the retention clips
into the strut, and glue.
Be careful not to accidentally glue the
retention clips into the tubes, or you will be
unable to remove the strut from the wing.
Bend the jury struts to shape using the
appropriate pattern. Slip the strut into the
holes in A2/A2A, align vertically, use thread
to lash them to the lift strut, and secure with
thin CA.
August 2010 35
Add the 1/16 x 1/8 balsa strut fairings to
the jury struts to complete the process.
Landing Gear: Employing the patterns
provided, bend the landing gear components
to shape from the appropriate wire sizes. Lay
out the front strut and solder together using
Stay-Brite silver solder. Tape the front and
rear struts to the fuselage and solder.
Remove the landing gear assembly from
the fuselage and wash it with soap and water
to prevent corrosion. Now use thread to bind
the landing gear assembly to the beams, and
secure with thin CA. Add the 1/8 scrap balsa
gussets and 1/16 balsa fill.
Use the patterns provided to make the boot
cowl sections from yellow file-folder material,
and adhere them in place with white glue.
Start with the bottom, go to the sides, and then
bond the top.
To complete the fuselage assembly, build
the upper and lower cabin side doors directly
over the plans, from the wood sizes shown.
Sand to shape.
Mounting Servos and Motor: Glue servo
mount rails and beams in the fuselage. Space
the rails to fit your specific unit.
Screw the servos in place and run in the
elevator pushrod tube (Sullivan item 507),
supported at both ends and in a couple of
places in the middle using standoffs made
from short sections of the included pushrod
sheathing. The pushrod will be made from
.025-inch-diameter wire.
Fit the rudder and elevator into the
fuselage, and run in the rudder pull-pull cables
using the routing diagram on the plans. Tie
the cables off on the toothpick control horn
and note the exact location where the cable
will exit the covering. Mark that location on
the plans.
Set up the motor and ESC, and test the
system for proper rotation. Fit the motor onto
the mount stick and secure it with a dab of
silicone adhesive.
Now is a good time to assemble the model
and double-check for problems that might
arise. If an issue crops up, fix it now, while
things are still easy to access.
Covering: You can cover the Cub with tissue,
light silkspan and dope, or iron-on covering.
The best choice for iron-on is Coverite
Airspan or Litespan, if you like the dopedtissue
look. A good Mylar is Coverite
Microlite, also sold as Nelson Hobby
Specialties’ LiteFilm and So-Lite. Whatever
you choose, follow the manufacturer’s
instructions for best results.
I don’t recommend iron-on materials such
as MonoKote or UltraCote; their excessive
shrinking qualities will damage the light
structure, and the excessive weight will
adversely affect the model’s flying qualities.
Begin by covering all frames except the
vertical fin and fuselage top. With the frames
covered, plug in the wings and fit the
horizontal stabilizer in the fuselage, align
using the wings for reference, and adhere in
place.
Align and glue in place the vertical fin.
Cover the top of the fuselage and vertical fin
using a separate piece of covering for the leftand
right-hand sides, to form the fillet at the
base of the fin.
The side door is hinged to the fuselage
using hinge tape or covering material. Add
trim as desired. Callie Graphics has the trim
scheme for my model. Callie can also provide
custom graphics for any desired scheme.
Final Assembly: You can carve the cowl and
dummy engine from blue foam or balsa, or a
vacuum-formed cowl is supplied in the
previously mentioned parts pack. Fit the cowl
to the fuselage and screw it in place with
small sheet-metal screws.
Seal struts with a couple coats of waterbased
varnish or dope. Paint them with Model
Master Acryl.
Glue hinges in place in the rudder and
elevator, and fit them onto the model using
Pacer Formula 560 Canopy Glue or
equivalent. Run in the elevator pushrod, Zbend
the back end, and, with the elevator in
neutral position, glue the control horn in
place.
Mark exit points for rudder cables on the
fuselage. Reinforce the covering with tape or
vinyl trim stock, and pierce the covering at the
exit points. Run the rudder cables into the
fuselage and tie the cables to the control horn.
Drill the holes in the vertical fin and
horizontal stabilizer, and run in the tail-brace
rigging using light Kevlar thread. Adhere the
aileron hinges in place.
Make aileron pushrods from .032-inchdiameter
wire, with Z-bends on both ends. Fit
the rods onto the servo and control horn,
align the aileron to neutral, and glue the horn
in place.
Use brass tubes to size the holes in the
wheels down to 3/32-inch ID. Fit the 3/32-inch-
OD tubing to the axles and epoxy in place.
Mount the wheels using Du-Bro E/Z
Connector plastic keepers on both sides of
each. Fit and glue the side windows and
windshield using .005-.008 acetate. Add
remaining details you desire to finish the J-3.
With it basically ready to fly, set the CG
as shown on the plans, using battery and
receiver locations to your best advantage.
Mount the components on 1/16 hard-balsa
plates, using Velcro to secure them in place.
Set up controls as the plans show, and
you’re ready to go.
Flying: The three-channel Cub is easy to fly
but is slightly sensitive to windy conditions,
so it’s best to test-fly on a calm day.
Before the first flight, double-check the
control throws and ensure that they are
moving in the right direction. It’s no fun to
learn that one (or more) of the controls is
backward after liftoff.
The model should trim for straight and
level flight at approximately two-thirds
power. The controls are positive but not
overly sensitive.
The same rules apply to the four-channel
version, but on takeoff the rudder is
controlled with the left hand. Typical of the
Cub, the ailerons will induce a bit of adverse
yaw, so a bit of rudder is needed to
coordinate the turns.
Rudder can also be mixed with aileron
input, but doing that will make sideslipping
much more difficult. The Cub is a lot of fun
and wonderful at sideslipping. Differential
throw can also be mixed into the ailerons, to
help eliminate adverse yaw.
Otherwise, the little J-3 flies wonderfully.
It handles well and slows nicely for terrific
touch-and-gos.
This airplane will also do nice scale loops