Top Flite J-3 Piper Cub - Manual (Page 13)

vent "snaking". The location of the rudder and elevator
horns should be established, the holes drilled but not installed
until after covering. The aileron servo should be first mounted
to the manufacturer's aileron servo tray. The tray is then
mounted to a 1/16" plywood plate that has been cut to size.
The plate is then epoxied in the correct position to the inside
roof of the cabin. The flexible inner nyrod ends that connect
the ailerons to the servo can accomodate virtually any servo
type and output arm available. Make sure the servo installa-
tion works smoothly before covering. The throttle servo is
installed after the plane is covered and the engine installed.
STRUTS
IMPORTANT NOTE: THE WING STRUTS ON YOUR J-3 CUB
A R E FULLY FUNCTIONAL AND A R E ABSOLUTELY RE-
QUIRED FOR FLIGHT. THEIR ASSEMBLY, FIT AND ATTACH-
MENT A R E CRITICAL. DO NOT DEVIATE FROM ANY OF
THE FOLLOWING INSTRUCTIONS:
1. The wing struts provided (4) are 9/32" x 11/16" x 27" hard-
wood, preshaped. Very little sanding should be required to
smooth their surface. Extra length has been provided to allow
a mistake or two achieving the correct angles. Beveling these
parts to fit flush with the bottom of the wing is important
and should be done carefully. Note that none of the wing
struts are interchangeable. There must be a left-front, left-
rear, right-front and right-rear. In order to avoid confusion it
is suggested that you make a front and rear strut for one
panel, mark them as such, set them aside and proceed to the
opposite set.
2. Start by assembling the right and left wing panels to the fuse-
lage and securing with the 1/4"-20 nylon bolts provided. At-
tach the brass strut plates to the bottom of the fuselage as
shown on the plans. Set the assembled airplane upside down
on a flat surface — linoleoum floors work well — with a 1/4"
spacer between the top of the fuselage and the flat surface.
This will impart a slight amount of dihedral to the wings as
in the full scale Cub.
3. As mentioned in No. 1 above, start with either the right or
left side, beginning with the F O R W A R D strut. Prop up one
strut, on edge, directly over the front view of the wing/strut
joint on plan sheet No. 2. Remember there is a left and right
strut. Using a razor saw, carefully saw off the end of the
strut at the angle shown on the plans. Next, take this strut
over to your inverted model and, holding the cut angle against
the forward outboard strut plate, make sure that the inboard
end of the strut is at approximately the right location to en-
counter the brass strut plate. Note that the strut at this
point is too long. It will be cut to length shortly. If the
angle at the end of the strut is not quite right, use a sanding
block to bring it to true. Using a 7/64" dia. drill bit, drill
the outboard strut-attach hole through the end of the strut
as shown on the plans, at a right angle to the bottom of the
wing. This hole is for clearance of the No. 4-40 machine
screw that mounts the strut to the wing. Slip one of the
No. 4-40 machine screws provided through the hole you've
just drilled and into the blind mounting nut in the wing.
Tighten this screw just enough to create an impression of the
screw head in the wood. Remove the screw. With a grinder,
knife or sanding block, create a small "flat" around the hole
to allow the head of the screw to sit flush to the wood when
in place. As shown on the plans, epoxy one of the No. 4
steel washers provided, to the strut, over the attach-hole.
When dry, attach the strut to the wing.
4. The inboard end of the strut is simply cut to lenth as shown
on the plans. Remove the strut from the wing. With a 1/16"
dia. drill bit, drill the guide hole for the No. 2-56 x 1"
threaded stud that is to be tapped 1/2" into the inboard end
of the strut. Do not drill this hole any deeper than 9/16".
Tape off 1/2" of the No. 2-56 x 1" stud with masking tape,
dip the exposed end into 5-minute epoxy and "screw" this
end into the hole in the end of the strut to the depth of the
masking tape. Pliers can be used to hold the stud during this
operation. Wipe off any excess epoxy. Remove tape and
allow to dry. Thread one of the clevises provided onto the
exposed end of the stud and attach to the brass plate, in the
forward hole. Reattach the strut to the wing and fuselage
and proceed to make the rear strut. Follow the same pro-
cedure as above. Note that rear inboard end of the forward
strut must be trimmed as is shown on the plans to allow the
rear strut to fit closely to it.
5. The "interplane" struts are made from the two pieces of
.072" dia. x 12" wire provided. Their shape is depicted on
plan sheet No. 3, in Section A-A. Note: do not bend these
to shape until the two nylon mounting clips are first slipped
in place with their ends facing inboard, toward the fuselage
and flat against the front and rear struts. The ends of the
interplate strut fit into the eyelets provided in the wing. Note
that in the front view, the interplane struts exit the wing at
right angles to the bottom of the wing and are held in place
by the nylon fittings which are attached to the spars with the
No. 2 x 1/4" wood screws provided also. The ends of these
struts ride free in the eyelets for removal.
6. We strongly recommend that you cover your struts with Fab-
rikote. This will further strengthen these struts and, if you
are using Fabrikote to cover the rest of your Cub, they will
be color coordinated and ready to use. If you are planning
to use any other covering, we recommend that you fiberglass
the struts and paint to match.
COVERING AND FINISH
The full-scale J-3 Cub is almost completely fabric covered. This
covering kept the weight down and added strength. Your Cub,
being an accurate scale model not just in outline but in construc-
tion sense as well, requires the same considerations. Top Flite's
FABRIKOTE is the perfect covering material for your Cub. It is
extremely light, woven aircraft fabric that is very strong and is
pre-finished and ready-to-use. The PIPER YELLOW color in
FABRIKOTE will yield a perfectly finished J-3 PIPER CUB. On
plan sheet No. 1 you will find the Fabrikote cutting layout. Note
that this layout is approximate and your covering techniques may
increase or decrease some of the dimensions shown.
All of the individual parts of our prototypes were covered separate-
ly; ailerons, doors, stabilizer, rudder, elevators, struts, wing panels
and the fuselage. Only after covering did we hinge the surfaces,
add the windshield and windows, the window support dowels
(3/16" dia. provided), install the cowling and add any of the de-
tails.
The one piece cowl is matched to the Fabrikote PIPER YELLOW
color and requires no additional finishing. If you wish to paint
the cowl we suggest using an epoxy-type paint, color mixed to
match, after first sanding with No. 600 paper, wet. Note that we
have provided an accurate, correct scale 3-view drawing of the 4
cylinder Lycoming engine used in many of the full scale Cubs.
These details can be added using plastic, metal, wood and a little
craftsmanship.
The 3-sheet set of mylar decals will complete your Cub. The lo-
cation for these decals are called-out on the plan sheets.
Be sure to give the firewall area of the fuselage a liberal coat of
polyester resin or epoxy glue to fuel proof it and to seal the nose.
Be careful not to get any resin or glue into the cowl mounting
block screw holes.
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