Top Flite J-3 User Manual
BUILDING
THE
PIPER
J-3
CUB
INTRODUCTION
Top Flite is proud to present it's large, scale version of the legendary J-3 PIPER CUB. Few aircraft in the history of aviation have
had the overall appeal of this rugged, good-looking little airplane.
"Cubs" have been used in a wide variety of roles including; trainer, bush plane, ranch work, crop duster, float plane, military and
just for all-around fun. The gentle "lightly-loaded" flying characteristics of the original J-3 Cub have been faithfully reproduced
for you with this kit.
In the "clipped wing" configuration, your Cub takes on a somewhat more acrobatic nature. The
has been the star performer of many an airshow and some of this
country's best-known acrobatic pilots such as Bevo Howard,
Pappy Spinks, Charlie Hillard, Pete Meyers, etc....started their
acrobatic careers in "clipped wing" Cubs.
Our kit offers you the choice of building either the full-span J-3
or the "clipped wing" variant. The only changes needed to build
the "clipped wing" version is to shorten the wing as shown on the
plans and to shorten the length and mounting angle of the struts.
With either version, your Cub will be an outstanding scale model
of the real thing, with flight characteristics to match. When your
Cub is covered with Top Flite's PIPER YELLOW FABRIKOTE.
no additional finishing will be necessary. Even the one piece
molded cowl has been color-coordinated to the FabriKote and it,
too, is ready-to-use without the need of paint. FabriKote will
also give your Cub a tremendous amount of structural integrity
by virtue of it's ability to shrink drum-tight and stay that way.
The construction of the Cub is straight-forward and only requires
attention to both the plans and this instruction manual. Since
the Cub contains so much open structure to duplicate the
original, techniques such as accurate joints and complete glueing
are very important.
full
scale
"clipped
wing"
Cub
The construction sequence in the instruction manual has been
proven to provide quick and accurate assembly. Do not deviate
from the instruction manual. Read through the manual first
while reviewing the plans BEFORE starting actual construction. Often this will clear-up questions that might not be understood during construction.
Our production prototypes of the J-3 Cub used standard frontrotor .40 engines with mufflers. Props used were Top Flite 11 -4
Power Props. Radios were standard 4-channel types with medium
output
servoes.
Flite's PIPER YELLOW FabriKote (see box label). Calculated
data on our prototypes is as follows:
Wing Area
Weight
Wing Loading
Our
airplanes
STANDARD SPAN J-3 "CLIPPED-WING"
795
Sq.
76
Ozs.
13.77 Ozs./Sq. Ft.
Ins.
were
covered
completely
595 Sq. Ins.
72 Ozs.
17.43 Ozs./Sq. Ft.
with
Top
WING
These instructions apply to both the "clipped wing" and full-span
wings. The "clipped wing" version requires that W-1/W-2/W-3
root rib lamination be moved outboard to the position shown on
the plans, sheeting applied like the root section shown, the interplane eyelets be moved outboard on the W-13's and the struts
shortened accordingly. The instructions assume that you will
build both wing panels simultaneously.
GLUE JOINTS
Our prototypes were built using a variety of adhesives - aliphatic
resin, cyanoacrylate and 5—minute epoxy. We recommend that
you use any or all of these as you require.
The tools required to build the Cub are those found in the average
modeler's workshop. You should have a work surface that is large
enough to accomodate an airplane of this size, and it must be flat!
"Beaver board" or Celotex is an excellent surface to work on as
it readily accepts pins. Sharp, single edge razor blades, an X-acto
knife, a power drill and bits, T-pins, a good metal straightedge, soldering iron, hobby saws, sanding blocks and a variety of
sandpaper
When removing the die-cut parts from their sheets, always keep an
X-acto knife handy. Do not force these parts from the sheet, use
the knife to carefully cut on the outline of the part and then
gently remove them. Remove only the parts that you require for
a
particular
needed. Touch-up sand any of the parts that may need it and
always trial-fit the parts in place before glueing, some trimming
may be required. The technique of double glueing all joints,
especially in an airplane of this size is advisable
1
grades
will
be
used
construction sequence,
in
construction.
leave
the others
in
place
until
1. a. Glue wingtip pieces W-16, W-17 and W-18 together and
allow to dry.
b. Glue aileron bellcrank tray supports AT-1 to ribs W-6 and
W-7. Note these parts face each other in the rib bay between ribs W-6 and W-7.
c. Glue the 1/16" thick W-3 (PLY) rib to the inside of the
1/4" balsa W-2 rib. Note there is a right and a left W-2/W-3
laminate, one for each wing panel.
d. Trim the wingtip ends of both 1/4" x 5/8" x 36" main
spars
and
both
1/4" x 3/8" x 36"
plans.
2. Using the 4 pieces of 1/4" x 5/8" x 21" balsa provided, cut 2
aileron spars as shown on the plans — these are 19-3/8" long.
Pin these directly to the plan, between rib location W-4 and
W-9. The 2 remaining pieces will become the aileron leading
edges.
Trim
these
to
19-5/16"
glue, tack glue these pieces directly to the back of the aileron
spar
already
aileron cross-section on plans.)
in
place and secure
rear
spars
as
long. Using a few
with
pins.
(Refer to
shown
"dots"
the
on
of
rib/
3. Using the 1/16" x 1/4"
19-5/16" length directly to the rear, bottom of the aileron
leading edge, flat against the plans.
4. Position and pin the bottom 1/16" x 1" x 36" trailing edge
(T.E.) stock to the plans. Note this material ends at the outboard W-12 aileron riblet location — let the excess extend inboard past the W-1. W-2. W-3 location as it will be trimmed
x 36"
cap strip stock provided, glue a
later.
5. Using the 1/16" x 1/4" x 36" cap strip material provided,
measure, cut and glue in place the bottom outboard and inboard aileron cap strips, between the T.E. and the aileron
L.E. cap strip. Note: do not add the other bottom aileron
cap strips at this time.
6. With a razor blade, carefully cut away the T.E. sheeting and
aileron cap strip to accept the 1/16" ply aileron horn plate —
W-19 (PLY). Glue W-19 (PLY) in place.
7. Locate and remove all W-12 aileron riblets from their die cut
sheets. Glue all W-12 riblets in place directly to the aileron
L.E., the aileron L.E. cap strip and the bottom T.E. sheeting,
using the plan for location and spacing. Be sure these are
installed 90° upright and square with plan.
8. Develop Wing Construction Spacing:
a. Pin the bottom, forward 1/8" x 1/4" x 36" sheeting spar
directly to the plans — locate accurately.
b. Directly behind this spar, lay a piece of the 1/16" x 1/4"
x 36"
cap strip stock to serve as the forward rib spacer —
it is not necessary to pin this in place.
c. Directly forward of the aileron spar, lay a piece of the
same
cap
strip
material. This
spacer.
9. Locate and carefully remove all remaining wing ribs from
their die-cut sheets. Carefully remove the die-cut spar cutouts (this is most easily done with the use of an X-acto knife
with a No. 11 blade). "Thread" each rib, in their appropriate
order, over forward 1/4" x 5/8" x 36" main spar and the 1/4"
x 3/8" x 36" rear spar, making sure that the trimmed wingtip
ends of each spar are at the wingtip and are turned up on the
correct side. Space the ribs approximately as shown on the
plans.
10.
Once all the ribs are in place over the plans, the assembly
should be carefully inspected to make sure that each part that
is to contact another, does so. If any trimming is required to
ensure the wing lays flat to the work surface, this is the time
to
do
it.
will
serve
as
the
rear
rib
2
11.
Glue the bottom end of each full rib (W-2/W-3 (PLY), and
all W-4's to the 1/16" x 1" x 36" bottom T.E. sheeting. The
outboard W-4 rib is also glued to the inboard end of the
aileron spar, BUT NOT the aileron L.E. Notice the 1/32" resulting gap between the inboard W-12 aileron riblet and the
outboard end of the W-4 rib. This is the correct spacing for
the wing/aileron relationship.
Glue each of the remaining partial ribs (W-5, W-5, W-6, W-7,
W-8 and
on W-6 and W-7 must face each other.
Glue rib W-9 to the outboard end of the aileron spar — not
the aileron L.E.
The W-10 rib is left loose on the spars for the time being.
W-8)
to
the
aileron
spar — remember
that
the
AT-1's
16. Prepare the top forward 1/8" x 1/4" x 36" sheeting spar for
installation by first trial fitting it into place into the rib slots —
relieve any rib slot that might force this spar out of true.
Score the spar just outboard of rib W-9 and lightly "crack" it
downward. Bevel the tip end of the spar to mate flush with
the wingtip as shown on the plans. Glue the spar in place,
into
each
rib
and
to
the
wingtip.
to
dry.
17.
Remove all of the W-11 "false ribs" from their die-cut sheets.
These can now be glued in place onto the 5/16" sq. L.E. and
into the top (only) 1/8" x 1/4" sheeting spar. These ribs
should be aligned with the plans and held securely with pins
until dry.
Secure
with
pins and
allow
12. The wingtip assembly W-16/W-17/W-18 should now be trialfitted in place. Note that this assembly must fit to the very
end of the W-9 rib while the spar slots line-up with the spar
ends and the forward tip piece, W-18, fits against rib W-9
and centered with the L.E. cut-out. At the same time, rib
W-10 must fit into the fore and aft slots provided in the tip
assembly. This is a matter of "fit and try" until you are
satisfied. Once the fit is correct, glue and pin the tip assembly in place as described above. Glue rib W-10 in place in the
slots provided. Allow this assembly to dry completely.
13.
Glue the
against each rib and the cut-out provided in the leading edge
of the wingtip — allow to dry.
14. Using a scrap glue stick, carefully and completely apply glue
(preferably a white glue or an aliphatic resin type) to each
rib/spar
amount of glue but rather to be sure that each joint is completely covered with adhesive, on both sides and top of the
joint.
15. Glue and pin the 3/32" x 1/2" x 36" trailing edge laminate
stock in place on the 1/16" x 1" bottom T.E., directly behind the ends of each rib and aileron riblet. Like the bottom
T.E. sheet, this stock runs from the outboard W-12 riblet, inboard past
trimmed later.
5/16"
joint.
the
sq. x 36"
NOTE:
W-2/W-3
leading
it
is
(PLY)
edge
not
in place. Secure
necessary
ribs.
to
The
firmly
apply a large
excess
will
be
3
18. Use a small sanding block and coarse sandpaper to bevel the
3/32" x 1/2" x 36" T.E. laminate to the shape shown in the
plans. Bevel the laminate only, do not sand into the 1/16"
T.E. bottom sheeting.
19. Glue the 1/16" x 1" x 36" top T.E. sheeting in place. Pin
securely and allow to dry.
20. Prepare the forward wingtip for sheeting by sanding a bevel
into it from the 1/8" x 1/4" top L.E. spar, forward thru the
5/16" sq. L.E., to provide seating for the 1/16" sheeting.
21. Glue and pin the 1/16" balsa top sheeting in place. It is
helpful to lightly score the sheeting just outboard of W-9 to
facilitate the slight compound curve required. Let this
assembly dry completely.
22. Glue all top 1/16" x 1/4" cap strips in place on all ribs, W-12
aileron riblets and W-11 false ribs with the exception of the
W-2/W-3 (PLY) ribs, the inner-most W-11 false rib and the
first inboard W-4 rib. This section will be sheeted later.
23.
Locate and remove the 1/16" thick W-19A (PLY) horn plate
doublers from their die-cut sheet. Glue in place on top of
horn plate W-19 (PLY), as shown on the plans. Locate and
remove 4 of the G-2, 3/32" balsa gussets and glue these in
place into each corner of each aileron as shown on the plans.
24.
Using a small sanding block and medium-to-coarse sandpaper,
lightly sand the protruding tops of the aileron spar and aileron
L.E. stock down to the airfoil level of the wing. These should
blend with the cap strips to create the finished airfoil (refer
to wing/aileron cross-section on the plans).
25.
Prepare the aileron bellcrank mounting trays W-20 (PLY) by
first drilling them per the dimensions given on the plans with
a No. 45 (.082") drill bit. Mount the 90° aileron bellcranks
to the trays as shown on the plans. These should work freely
but without "slop". Epoxy the trays into place on the AT-1
supports in the W-6/W-7 rib
bay.
26. Remove wing panels from the building board. Inspect each
panel carefully to be sure of good glue joints, etc. Now is the
time to clean-up each panel to prepare them for finishing.
Glue all the remaining gussets, G-1, G-2 and G-3 in place as
shown.
27. Carefully block-up each panel upside down on the building
board. Be sure that the panels are firmly pinned and blocked
in place and that they are truly flat. Prepare the bottom for-
ward 1/8" x 1/4" x 36" sheeting spar by first trial fitting it in
place into the slots in the ribs. Relieve any rib slot that might
force this spar out of true. Score the spar just outboard of
rib W-9 and lightly crack it. Bevel the tip end of the spar to
fit flush with the wingtip, as shown on the plans and glue the
spar into place. Secure with pins and allow to dry.
4
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