Top Flite Models Piper J-3 Cub User manual

BUILDING THE PIPER J-3 CUB

INTRODUCTION
Top Fliteis proud to present it's large,scale version of the legend-
ary J-3 PIPERCUB. Fewaircraftin the historyofaviationhave
had the overallappealof thisrugged, good-lookinglittleairplane.
"Cubs" havebeen used ina widevarietyof rolesincluding;train-
er,bush plane, ranchwork,cropduster,floatplane, militaryand
just for all-aroundfun. The gentle "lightly-loaded" flyingcharact-
eristicsof the originalJ-3 Cub have been faithfullyreproduced
foryouwiththiskit.
Inthe "clipped wing" configuration, your Cub takesona some-
what more acrobaticnature.The full scale "clipped wing" Cub
has been thestarperformerof many an airshowand some of this
country'sbest-knownacrobaticpilotssuchas BevoHoward,
Pappy Spinks,CharlieHillard,Pete Meyers, etc....started their
acrobatic careers in"clipped wing" Cubs.
Our kit offersyouthe choice of building eitherthefull-spanJ-3
orthe "clipped wing"variant.The only changes needed to build
the "clipped wing" versionis to shorten thewing asshownon the
plans and toshortenthelength and mounting angleof the struts.
Witheitherversion,yourCub willbe an outstandingscalemodel
ofthe realthing, withflightcharacteristicsto match. Whenyour
CubiscoveredwithTop Flite'sPIPERYELLOWFABRIKOTE.
noadditionalfinishingwillbenecessary.Eventheone piece
molded cowlhas been color-coordinatedto the FabriKoteand it,
too, isready-to-usewithoutthe need of paint.FabriKotewill
alsogive your Cub a tremendous amount of structuralintegrity
byvirtueof it'sabilityto shrinkdrum-tightand staythatway.
The constructionof the Cub is straight-forwardand only requires
attention to both the plans and this instruction manual. Since
the Cub containsso much open structureto duplicatethe
original,techniquessuch as accuratejointsand complete glueing
are very important.
GLUE JOINTS
Our prototypes were built using a varietyof adhesives - aliphatic
resin, cyanoacrylateand 5—minute epoxy.We recommend that
you use any or allof these as you require.
The toolsrequiredto build the Cub arethose found inthe average
modeler's workshop.Youshould have a work surfacethatis large
enough toaccomodate an airplaneofthissize,and itmust beflat!
"Beaver board" or Celotexis an excellentsurfaceto workon as
itreadilyacceptspins. Sharp, singleedge razorblades, an X-acto
knife,a power drilland bits, T-pins,a good metal straight-
edge,soldering iron, hobby saws, sanding blocksand a varietyof
sandpaper grades will be used in construction.
When removing the die-cut parts fromtheir sheets, always keep an
X-actoknifehandy. Do not force these partsfrom the sheet, use
the knifeto carefullycut on the outline of the part and then
gently remove them. Removeonly the partsthat you require for
a particular constructionsequence, leave the others in place until
needed. Touch-up sand any of the parts that may need itand
alwaystrial-fitthe parts inplace before glueing, some trimming
may berequired. The technique of double glueingalljoints,
especially inan airplane of this size is advisable
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The constructionsequenceinthe instructionmanual has been
proven to provide quickand accurateassembly. Do not deviate
from the instructionmanual. Readthrough the manual first
while reviewingthe plansBEFOREstartingactualconstruct-
ion.Oftenthiswillclear-upquestions that might not beunder-
stood during construction.
Our production prototypes of the J-3 Cub used standardfront-
rotor .40 engineswith mufflers.Props used wereTop Flite11-4
Power Props. Radioswerestandard4-channeltypeswithmedium
output servoes. Our airplanes were covered completely with Top
Flite's PIPERYELLOWFabriKote(seebox label).Calculated
data on our prototypesis as follows:
STANDARDSPAN J-3"CLIPPED-WING"
795 Sq. Ins.
Wing Area
Weight
Wing Loading
595 Sq.Ins.
72 Ozs.
17.43Ozs./Sq.Ft.
76 Ozs.
13.77Ozs./Sq.Ft.
WING
These instructions apply to boththe "clipped wing" and full-span
wings. The "clipped wing" versionrequiresthat W-1/W-2/W-3
root riblaminationbemoved outboard to the positionshown on
the plans, sheetingappliedlikethe root section shown, the inter-
plane eyeletsbemoved outboard on the W-13's and the struts
shortened accordingly.The instructionsassume that you will
buildboth wing panels simultaneously.
1.a.Glue wingtip pieces W-16, W-17 andW-18 together and
allowto dry.
b.Glue aileron bellcrank tray supports AT-1to ribs W-6 and
W-7. Note these partsfaceeach other inthe rib baybe-
tween ribsW-6 and W-7.
c.Glue the 1/16"thick W-3 (PLY)rib to the insideof the
1/4"balsa W-2rib. Note thereis a right anda left W-2/W-3
laminate, one for each wingpanel.
d.Trimthe wingtipends of both 1/4"x 5/8" x 36" main
spars and both 1/4" x 3/8" x 36" rear spars as shown on
plans.
2.Using the 4 pieces of1/4"x 5/8" x 21" balsaprovided,cut 2
aileronsparsas shown on the plans — theseare19-3/8" long.
Pin these directlyto the plan, between riblocationW-4 and
W-9. The 2 remainingpieces willbecome the aileronleading
edges. Trim these to 19-5/16" long. Using a few "dots" of
glue,tack glue these pieces directlyto the back of the aileron
spar already in place and secure with pins. (Referto the rib/
aileroncross-sectionon plans.)

3.Using the 1/16"x 1/4" x36" cap strip stock provided, glue a
19-5/16" length directlyto the rear, bottom of the aileron
leading edge, flatagainstthe plans.
4.Position and pin the bottom 1/16"x 1"x 36" trailingedge
(T.E.) stock to the plans. Note this materialends at the out-
board W-12aileronribletlocation — let the excessextendin-
board past the W-1. W-2. W-3 location as itwillbetrimmed
later.
5.Using the 1/16"x 1/4"x 36" cap stripmaterialprovided,
measure, cut and glue inplace the bottom outboard and in-
board aileron cap strips, between the T.E.and the aileron
L.E.cap strip. Note: donot addtheotherbottom aileron
cap stripsat this time.
6.With a razor blade,carefully cut away theT.E.sheeting and
aileron cap strip to accept the 1/16"ply aileron horn plate —
W-19 (PLY).Glue W-19 (PLY)inplace.
7.Locateandremove all W-12 aileron riblets from their die cut
sheets. Glue allW-12ribletsinplace directlyto the aileron
L.E.,the aileron L.E.cap stripand the bottom T.E. sheeting,
using theplan forlocation and spacing. Be sure these are
installed 90°upright and square with plan.
8.Develop Wing Construction Spacing:
a.Pinthe 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 ofthe 1/16"x 1/4"
x36" cap stripstock to serveas the forwardrib spacer —
itis not necessary to pin this in place.
c.Directlyforwardof the aileronspar, lay a piece of the
same cap strip material. This will serve as the rear rib
spacer.
9.Locate and carefullyremove all remaining wing ribs from
their die-cut sheets. Carefullyremovethe die-cut spar cut-
outs (thisismost easilydone with the use ofan X-actoknife
with a No. 11 blade)."Thread" each rib, intheir appropriate
order,overforward1/4"x 5/8" x 36" main spar and the1/4"
x3/8" x 36" rear spar, making sure that the trimmedwingtip
ends ofeach spar areat the wingtip and are turnedup on the
correct side. Space theribs approximately asshown onthe
plans.
10. Once all the ribs are inplace over the plans, the assembly
should becarefullyinspected to make surethat each part that
is to contactanother, does so. If any trimming is requiredto
ensure the wing lays flat tothe work surface, this is thetime
to do it.
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11. Glue the bottom end of each fullrib(W-2/W-3(PLY),and
allW-4'sto the1/16" x 1"x 36" bottom T.E. sheeting. The
outboardW-4 ribis alsoglued to the inboard end of the
aileronspar,BUT NOT theaileronL.E. Noticethe1/32" re-
sulting gap between the inboard W-12aileronribletand the
outboard end of the W-4 rib. This isthe correctspacing for
the wing/aileronrelationship.
Glue each oftheremainingpartialribs (W-5, W-5, W-6, W-7,
W-8 and W-8) to the aileron spar — remember that the AT-1's
on W-6 and W-7must faceeach other.
Glue rib W-9 to the outboard end of the aileron spar — not
the aileronL.E.
The W-10 rib isleft loose on the spars for the time being.
16.Prepare thetop forward1/8"x 1/4"x 36" sheetingspar for
installationbyfirsttrialfittingitinto placeinto the rib slots—
relieveany ribslotthat might forcethisspar out of true.
Score thespar justoutboardofribW-9 and lightly"crack"it
downward. Bevelthe tipend ofthe spar to mateflushwith
the wingtip asshown on the plans. Glue the spar inplace,
into each rib and to the wingtip. Secure with pins and allow
to dry.
17. Removeallofthe W-11"falseribs"fromtheirdie-cutsheets.
These cannow beglued in placeonto the 5/16" sq. L.E. and
into the top (only)1/8" x 1/4" sheetingspar.Theseribs
should bealigned with the plans andheld securely with pins
until dry.
12.The wingtip assembly W-16/W-17/W-18 should now betrial-
fittedin place. Note thatthisassemblymust fitto thevery
end of the W-9 ribwhilethe sparslotsline-up withthe spar
ends and the forwardtip piece, W-18, fitsagainst rib W-9
and centeredwiththe L.E. cut-out.Atthe sametime, rib
W-10must fitintothe foreand aftslotsprovidedin the tip
assembly.Thisis a matterof "fitand try"untilyou are
satisfied.Oncethe fitis correct,glue and pin the tip assem-
bly inplace as described above. Glue rib W-10 inplace inthe
slotsprovided.Allowthisassemblyto drycompletely.
13. Glue the 5/16" sq. x 36" leading edge inplace. Secure firmly
againsteach riband the cut-out providedin the leading edge
of the wingtip — allowto dry.
14.Using a scrapglue stick,carefullyand completely apply glue
(preferablya white glue or an aliphaticresintype)to each
rib/spar joint. NOTE: it is not necessary to apply a large
amount ofglue butratherto be sure thateach jointis com-
pletely covered with adhesive, on bothsides andtop of the
joint.
15.Glue and pinthe 3/32"x 1/2"x 36"trailing edge laminate
stock inplace on the 1/16"x 1"bottom T.E., directlybe-
hind the ends of each rib and aileron riblet. Like the bottom
T.E. sheet, thisstock runs fromthe outboard W-12riblet, in-
board past the W-2/W-3 (PLY) ribs. The excess will be
trimmed later.
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18.Usea small sanding block and coarse sandpaper to bevel the
3/32" x 1/2"x 36" T.E. laminate to the shape shown inthe
plans. Bevelthe laminate only, donotsandinto the 1/16"
T.E.bottom sheeting.
19.Glue the 1/16" x 1"x 36"topT.E.sheeting inplace.Pin
securely and allow to dry.
20.Preparethe forwardwingtip for sheeting by sandinga bevel
into itfromthe 1/8"x 1/4"top L.E. spar, forwardthru the
5/16"sq.L.E.,toprovide seating for the 1/16"sheeting.
21.Glueand pin the1/16" balsatop sheetinginplace. Itis
helpful to lightly scorethe sheetingjust outboard ofW-9 to
facilitate the slight compound curve required. Letthis
assembly dry completely.
22.Glue alltop 1/16"x 1/4" cap strips inplace on all ribs, W-12
aileron ribletsand W-11falseribswiththe exceptionofthe
W-2/W-3 (PLY)ribs,the inner-mostW-11falseriband the
firstinboard W-4 rib. Thissection will besheeted later.

23. Locate and remove the 1/16"thick W-19A (PLY)horn plate
doublers fromtheir die-cut sheet. Glue inplace on top of
horn plateW-19 (PLY),as shown on the plans. Locate and
remove 4 ofthe G-2, 3/32" balsagussets and glue thesein
place intoeach corner of each aileronas shown on the plans.
24. Using a small sanding block and medium-to-coarsesandpaper,
lightly sand the protruding tops of the aileronspar and aileron
L.E. stockdown to theairfoillevelof the wing. Theseshould
blend with the cap stripsto create the finished airfoil(refer
towing/aileron cross-section onthe plans).
25. Prepare the aileron bellcrank mounting traysW-20 (PLY)by
firstdrillingthem per the dimensionsgivenon the planswith
aNo.45 (.082") drill bit.Mount the 90°aileronbellcranks
to thetraysas shown on the plans.Theseshould workfreely
butwithout "slop". Epoxythe traysinto place on the AT-1
supports inthe W-6/W-7 rib bay.
26.Removewing panels from the building board. Inspect each
panel carefullyto be sure ofgood glue joints, etc. Now is the
time to clean-up each panel to preparethem forfinishing.
Glue all theremaining gussets, G-1, G-2 andG-3 inplace as
shown.
27.Carefully block-up eachpanel upside down on the building
board. Be surethatthe panelsarefirmlypinned and blocked
inplace and thatthey are trulyflat.Preparethe bottom for-
ward 1/8"x 1/4" x 36" sheeting spar by firsttrialfittingitin
place into the slotsinthe ribs.Relieveany ribslotthatmight
forcethissparout oftrue. Score the sparjust outboardof
rib W-9 and lightlycrackit.Bevelthe tip end of thesparto
fitflushwith the wingtip, as shown on the plans and glue the
spar into place. Securewithpins and allowto dry.
4

28. Using a sanding block, bevel the wingtip from the 1/8"x
1/4"sheeting spar,forwardthru the 5/16" sq. L.E. to pro-
vide seating forthe 1/16"balsaL.E. bottom sheeting. Glue
andpinthe L.E.sheet inplace. Note that itis advisable to
lightly scorethe sheetingjust outboardof the W-9 rib to
facilitatethe slightcompound curverequired.Let this
assembly dry.
29. Locate and glue 1/16"thick parts W-15 (PLY),W-14 (PLY)
and both W-13(PLY)'sinplace per the plan. NOTE:besure
to glue the W-15(PLY)partsinplacecorrectlyto provide
exit ofthe threaded aileronpushrods fromthe bellcrank end.
30. Using the1/16"balsa sheet provided, sheet the wing root
from the inboard W-4 rib thru the W-2/W-3(PLY)ribnoting
graindirectionon plans. Glueallremaining wing and aileron
cap strips inplace andallow to dry.
31. Remove the wing panels from the work surface. Asbefore,
inspect them, remove any glueruns and makesurealljoints
are properlyglued. The panelscan now belightly sanded to
final shape withthe exception of rounding the leadingedges
tofinalshape. This willbedone later. Locate and gluethe
1/16"thickply strutplate doublersW-15A(PLY)and W-14A
(PLY) inplace on top of W-14 (PLY)and W-15(PLY).
32.Use a razoror hobby saw to remove the excess sheeting, L.E.,
T.E. and spar stock fromthe root of each wingpanel.
LIGHTLY sand the balance of this material flush with the
face of root ribW-2. Becareful tosand ONLY to theface of
this rib, not into it.
With a few exceptions, your wing panels are now complete. Pro-
ceed to the next construction phase of these instructions.
5
TAILSURFACES
Accuratejoints, complete glueing and a flatworksurfaceare
essentialto strong tailsurfaces.Cover stabilizerand rudder area
of plan sheet 1 withMonokote backingmaterialor SaranWrap
before beginning construction of these parts.
STABILIZER
1.Glue and pininplace all die-cut S-1's, S-2's, S-3 , S-4's and
the 1/4" x 1/2" balsatrailingedge. Using the 3/32" x 1/4"
stock provided, cut to size and glue in place the "ribs". Do
notglue the 1/8"x 1/2" gussets inplace yet.
1.Glue and pin inplace all die-cut E-1's, E-2's, E-3's, E-4's and
the 1/4" x 1/2" leading and trailingedges fromthe stock
provided. Cut and glue in place the 3/32" x 1/4""ribs".
Cut offa 3"length of 1/4" diameter dowel and epoxy in
place between the two elevatorhalvesas shown on the plans.
2.When the stabilizer and elevator assemblies have dried, remove
them from the worksurface.Inspect and clean-up each of the
glue joints.Usingthe 1/8"x 1/2"stockprovided,carefully
make and installeach ofthe gusset jointreinforcements,as
shown on the plans. Fit these to each joint, noting grain
direction and center them between the upper and lower
surfaces.
1.Glue and pin inplace die-cut parts R-1,R-4 and the 1/4"
x1/2" outlinestock.Note on the plans that the bottom,
trailing edge piece of 1/4"x 1/2" wood has an "extension"
cut into it's shape. This area is shown as cross-hatched (////).
Alsonote that 1/4"square balsa isused at the top of the fin
to complete it's outline. Glue the 3/32" x 1/4""ribs" in
place.
FIN
ELEVATORS

RUDDER
1.Glue and pininplace die-cut parts R-2, R-3 and the 1/4"x
1/2"outline stock. As withthe fin, note the piece of1/4"
sq.stock used to completethe outline, just above the top of
the fin. Glue the 3/32" x 1/4""ribs" inplace.
2.When the finand rudder assemblies are dry, remove them
from the worksurface.Inspect and clean-up the joints. Like
the stabilizerand elevatorassemblies,install the gussets,
centered between the outside surfaces.
Usea sanding block to sand the tailsurfaces tothe final outline
shape shown on the plans. Sand the surfacesto remove any high
spots.Finally, sandthefinalrounded cross-sectionshapesofeach
surface. Note that the R-1piece on the frontof the finmust
blend into the 3/16" diameter dowel used forthe "spine" stringer
on the fuselage. Each surfaceshould now beslotted forhinges
and set aside for covering and assembly.
FUSELAGE CONSTRUCTION SEQUENCE
Carefullyposition and tape plan sheets No.'s1 and 2 together,
using the dashed lines. The two fuselage sides will be constructed
one over the other to assure uniformity.These two sides are
identical except that the right side will have the lower access door
builtinto it.The instructionstakethis into consideration. To
further insure uniformity we advise that two each of brace, up-
right and longeron becut at the same time, when building the
firstside. Cover plan with Monokote backing or Saran Wrap
before starting.
1.Start theright side bypinning and glueing the two-piece 1/4"
square upper balsa longeron inplace.The forwardpiece is
from the frontofthe firewallto F-11position. The rear
pieceisfrom F-11 torudderhingeline.
2.Pinand glue the three piece 1/4"square lower longeron in
place. The forwardpiece is fromthe frontof the firewallto
thecenter of frontlanding gear block. The center piece from
the center of frontL.G.block to center of rear L.G.block.
The rear piece runs fromthe center of the rearL.G.block
back to the rudder hinge line.
3.Using the 1/4"squareand 1/8"x 1/4"balsa provided,
accuratelycut, glue and pin alluprights inplace. Note that
the front, bottom and rear 1/4" square door outline should
not beglued to the 1/4" squaredoor frame.Maintain a
slight gap all the wayaround the frame as the door willbe
cut freelater. Alsonote thatthe forward-mostnose upright
is recessed back 1/4"to allow the firewallto key inplace.
With the 1/4"x 3" x 12"balsa provided, measure, cut and
glue the fillersinto the frontof the fuselage.
4.Allowto dry and remove pins. With a sanding block, lightly
smooth the frame. Cover framewithMonokote backingor
Saran Wrapand repeat steps 1,2 and 3 — deleting the door
outline, building the leftframedirectly overthe right one.
5.When dry removebothframesfromthe worksurfaces.Inspect
and clean-up the joints. We suggest double-glueing these
joints. Lay the sides back over the plans and with a soft
pencil, markthe location of formersF-2,F-10 (markthe
location of this formeron the INSIDE of each frame),F-11,
F-4,F-5, F-6, F-7, F-8 and F-9. Last, mark the location of
the1/8"x 1/4"tank shelf supports at thenose.
6.Sand a shallowjoining taper into the inside ofeach fuselage
atthe tailpost. Remember the rightfuselagesidehasthe door.
This taper should resultin the tailpost ofeach framemeasur-
ing1/8"inwidth, 1/4"when held together.
7.With the 1/8"balsasheetprovided,cutfour17-3/4" lengths.
Using a flatsurface,"butt-glue" twopieces together to form
arough fuselage side, which should then measure1/8"x 6" x
17-3/4". Repeat this step withthe remaining two pieces.
6

Cut two fuselagesides.Note that at the furthestaftpoint the
fuselagesideends at F-4 on the top and anglesforwardto the
bottom as shown on the plans. At thenose, the sides extend
past the firstupright to the ends of thetop and bottom long-
eron. The firewallfitsinside of the fuselagesides.
With the fuselage side frames laying face down on the work
surface,remember thatthe right side containsthe door, glue
the 1/8"sheet fuselagesidesto the right and leftfuselage
frames. Pininplace. Glue die-cut pushrod exitsheets F-23R
(for right side)and F-23L at the end of each fuselageframe.
Pininplace. Gluethe 1/8" squaretop longerondoublerin
place between the end of the fuselagesideand thefrontedges
of F-23R and F-23L. Locate positionof,and glue the
"center" 1/8" square stringer in place along fuselage framing
between fuselagesheeting and F-23Rand F-23L.
When the fuselagesideassembliesare dry,place them accur-
atelytogether and sand theiredges witha sandingblock to
assureuniformity.
Witha hobby saw or a razorblade, score the longerons of
each fuselagesidejust behind the second 1/4"square up-
right, both the top and bottom. Turn the fuselagesides over
and scorethe 1/8" sheetingalongthesame line represented
bythe back edge of the second fuselageupright. Do not cut
all the waythrough butenough to allowthe fuselagesidesto
be"cracked"inwardalong the scored lines. Place the fuse-
lage sidesdown on the edge ofa table, longeron side down,
withthe scored line justabove the tableedge. Carefully
pressdown on the section ahead of the scoredline and crack
it.Dothe same for the opposite fuselage side.
8.Glue F-5A to F-5B to formformerF-5. Glue all 1/8"x
1/4"braces to F-5, F-6, F-7, F-8 and F-9. Allowto dry.
Cover bottom view of plans with Monokote backing or Saran
Wrap. Carefullycut, glue and pin allbottom 1/4"square
and 1/8"x 1/4"cross-piecesand diagonals overplan.
Position rear landing gear block over plan with the slot facing
down and the widest area of theblocktoward therear.
Secure with pins.
7
9.Pin andglue the rightandleft fuselage sides over theplans
and to the cross-pieces,diagonals, the rear landing gear block
and to each other at the rear tail-post.Use a triangle to keep
the sides at 90°to the work surface.
Glue, position and pin formersF-4 (PLY),F-5, F-6, F-7,F-8
and F-9 to top rearof fuselagesidesusing the pencil marks
made earlierfor location. NOTE: these formersdo not sit at
90°to the top of the fuselagelongerons, they "lean" slightly
towardthe rear of the fuselage as shown on the plans. Allow
gluetodry.
Bevel the ends of the forward landing gear block to match
those shown on the plans. Glueforwardlanding gear block
in place, slot down. Note that the edges of this block will be
beveled later to match the fuselagebottom.
Trimnotches of former F-3 slightly to allow itto sitatthe
angle shown onthe plans. Glue former F-3inplace.
Trial-fitformer F-11(PLY)inplace, referringto Section D-D
on plans. F-11(PLY)must fitbetween the two1/4" square
uprights inthissection and directlyon top of the 1/4" square
top longerons. Trim if necessary to fitandepoxy inplace,
centered on the uprights.
Using the locationmarksmade earlier,trial-fitforwardformer
F-10 (PLY)inplace.Note that the installationof F-10
(PLY)requiresthatthe bottom nose areaof the fuselagebe
pulled in slightly.Glue the 1/8"x 1/4" tank supportsin
place using earliermarks. Epoxy F-10 (PLY)inplace and
secure with tape until dry.
Glue F-19 stabilizersupports inplace at the rear of the fuse-
lage. They glue to the top of the longerons, againstF-9 with
theouter surfaceflush with the top 1/8"stringer — see
Sections J-J and K-K on plans.
Cut and glue 1/4"square nose cross braces inplace between
top and bottom longerons.Glue the lasttwo nose formers
F-1 and F-2 in place. Glue the top centerlength of 1/8"x
1/4"stringer inplace inslotsinF-1,F-2and F-3.
When dry,remove fuselage from the building surface, inspect
joints, clean them up as required, double glue ifnecessary
and proceed to next step.

10. NOTE: This step assumes that you will be mounting your
engine to the right side as shownon the plans.
Carefullycut-outthe firewalltemplateprovided on plan
sheet No. 2 and lightly glue itto the 1/4"plywoodfirewall.
Drillfour 3/16" diameter holesinthe firewallusing the tem-
plate as a guide. Using the No.4-40 x 5/8" bolts and the
No. 4-40 blind mounting nuts provided,installthe motor
mount to the firewall.Tighten the boltsenough to forcethe
blindnuts into theback of the firewall.Carefullyremove
the bolts and epoxy the blind nuts tothe back of the fire-
wall— DO NOT get any epoxyinto the holes of the nuts but
apply epoxy around the edges to retain theminplace.
Epoxy both F-12(PLY)forwardlanding gear block supports
inplace on theinsideofthe fuselage. Alsoepoxy both F-13
(PLY)rearsupportsin place.
Using two 5"lengths of the 1/4"x 3"x 24" balsaprovided,
coverthe bottom of the nose areafromthe forwardlanding
gear block tofirewall— see sideview. Trimthe excessflush
with the outer fuselage sides.
With the 3/32" sheetprovided, plank the top nose area from
F-3 forwardto firewall.This is done withtwopieceswith
the joiningseam on top of the 1/8" x 1/4" balsastringer.
Sand flush with rear faceof F-3 and frontoffirewall.
MOTOR MOUNT
Trial-fitthe firewall into the nose of the fuselage. You will
note that itwillbenecessaryto slightlyrelievethe top fuselage
cross-braceand the faceof F-1to allowthe firewallto fit
flush.Itmay also be necessary to trim the firewallslightly to
fitproperly.
Using the remainder of the 1/8"sheeting used for the fuse-
lage sides, cut, trim and fit two pieces of this stock, cross-
grained as shown on the plans, to become the fuel tanktray.
This is most easilydone bymaking one piece to fitahead of
F-10 (PLY)and a second tofitbehind it.DO NOT cut into
F-10 (PLY)to fitthese pieces. Workaround it.Glue the
tank tray pieces inplace on the 1/8"x 1/4"supports.
Epoxy firewallinplaceagainstuprights, cross-braces, F-1and
tank tray.
11. Fitand glue1/4"die-cut bottom nose sheet F-18 inplace.
This part fitsflushwith the bottom longerons.With the re-
maining 1/8"sheet balsa, fillinthe bottom of the fuselage.
cross-grained,from the back of F-18 to the frontlanding
gear block, between the frontand rear landing gear blocks
and from the rearlanding gear block to the first1/4" square
bottom cross-brace. This sheeting fitsflush with the bottom
longerons.
12. Carefully remove the two plywood cabin frames, F-14 (PLY)
and F-15 (PLY),from their die-cut sheets. Removethe
window cut-outsfromthe frames.Note that F-14(PLY)is
the right side cabinframeas itcontainsthe upper door half.
Removethisdoor sectionfromF-14 (PLY)and set itaside
along with the windowcut-outs. Clean-up allofthe inside
window frame edges with a sanding block as required.
8

Epoxy F-14 (PLY)and F-15 (PLY)inplace, on top of the
fuselage longerons, against formersF-10 (PLY),F-11(PLY)
and F-4 (PLY)and keyed into the tabs on F-10 (PLY)and
F-11 (PLY).Tape this assembly securely inplace and allow
glue to dry completely.
Laminate and glue F-17 (PLY) toF-16 (1/4"balsa). Make a
similar second part butmake itjust the opposite sothat you
have a right and leftF-16/F-17(PLY)assembly.
Glue these two assemblies inplace against the insides of F-14
(PLY)and F-15 (PLY)withthe F-17(PLY)facingeach other
inthe cabin. Align and firmly clamp these assemblies until
completely dry.
13. With the 1/16" sheet balsa provided, cut and fit the "shelf"
that sitson the fuselagetop longerons just infrontof F-4
(PLY).Glue inplace.
With the 1/4"balsa sheet provided, accuratelymeasure, cut
and fitthe top cabinsheetinginplace from the back of F-10
(PLY) to the frontof F-4 (PLY).Note cross-graindirection.
THE PIECES MUST FIT ACCURATELYTO ACHIEVE
THE MAXIMUM STRENGTH. Once satisfiedwith the fit,
epoxy these parts inplace and allow todry.
Carefully trim and fitthe triangularcross-piece block that
sitson the frontof F-10 (PLY)and between the F-14 (PLY)
and F-15 (PLY)cabin sides — see sideview.Glue thisblock
inplace. Next, we haveprovided one block withtwo radiused
ends. Using the top viewon plan sheet No.2,cut two top
forwardwingblocks. Epoxy these two blocks inplace against
the triangularblock and F-14 (PLY)and F-15 (PLY).They
willbefinal shaped later.
14.Use a piece of scrap 1/4"sheet to rest on top of the two
F-19 stabilizersupports, to fillthe stabilizerslot. Trial-fit
the finin place as shown on the plans. Note thatwhen
properly inplace, R-1contactsF-9 and the trailingedge of
the fin lines up withverticalend of the fuselage. Once satis-
fied, glue the fininplace against F-9 at the frontand at the
rear, the small cross-hatched areaof the fintrailingedgeon
top of the F-19's (see side viewofplans).Use pins and tape
to assure the fin is truly vertical to the fuselage. Allow to
dry completely.
Frame the left cabin side F-15 (PLY) windows with 1/8"x
1/4"stock provided. The 1/8"side fitsagainstthe plywood.
Onthe leftsideonlythe areaon top of the fuselagelongeron
from F-10 (PLY)to F-11(PLY)and the two upright window
frames receivethismaterial. On the right side, F-14(PLY),
the upper door receivesthe same treatment exceptthat itis
completelyframedaround its perimeter aswell asthe two
upright window frames.
9

Removethe 1/4"die-cut F-21finsupports fromtheirsheet.
Note that these fitinplace inthe notches providedon each
side of F-9, back to the trailingedges of the fin. Bevelthe
inside edge of each F-21 to fit flush with the fin and glue in
place. Allowto dry.
15.Note that notches have been provided inall formers from
F-4 (PLY)thru F-9. These are to support the three 3/16"
dia. stringer dowels. The two sidedowelsareto blend
smoothly withF-21at the tail.The center dowel is to blend
with the roof line as shown on the top viewofthe plans and
at the tail it "carries thru" the fin shape at R-1. Sand and
trim the dowelsas required. Fit them inplace, relievingany
former thatmight forcethem out of true. Gluedowelsin
place and secure with tape until dry. Remove the 1/4" scrap
filler from the stabilizer slot.
Using a sanding block and medium paper, sand the F-19, F-21
and the stringerdowelsto the cross-sectionshapes shown on
the plans.
16. Trim F-22 (PLY)tailwheel mount to fitinside of the tail-
wheel bracket.Asshown on the plans, epoxya wedge of
1/4"balsa to F-22(PLY),sand to shape and epoxyto the
bottom ofthe fuselage at the tailpost.When dry,mount the
tailwheel bracket to the F-22 (PLY) base with the No. 2
screwsprovided. Do not overtightenscrews. Bend the tail-
wheel wireto the shape shown WITHOUT the "L" bend at
the top. Insert the wireinto the nylon bracket and then
bendthe 90°"L" bend that goes into the rudder. Drilla
pilot hole in the rudder for the small length of brass tube
provided and epoxy this tube inplace. Makea slotbelow
the tubing to clearthe tailwheelwireinthe rudder. Remove
thetailwheel assembly from the fuselage.
17. Sand entire fuselage tofinal shape. Take this time to inspect
joints, double-glue as needed. Do any fillingthat might be
required. The shaped blocksahead of the cabin carrythru
the leading edge shape of the wing. Itis advised that these be
rough-carved to shape and finalsanded only when thewing
panels are mounted to the fuselage.
18.Ifyou are planning to install a top observation window over
the cabin (window material not supplied),take the measure-
ments forits sizeand location fromthe plans and cut itout
of the 1/4"cabin sheet. Our prototypes used .020"butyrate
for this detail.
LANDING GEAR
Note thatthe landinggear wireshavebeen essentiallypre-bent to
shape. Itmay benecessaryto slightlycorrectsome of these
bends during assemblywithpliersor a vise.Takethe time to be
sure that these wiresfitwellwith one another. Beforeassembly,
clean off the wires with a degreasing agent, such as alcohol, ace-
tone, etc. A good techniqueis to sandthese wireswithNo. 400
sandpaper around the areas that are to besoldered before assem-
bly.
1.Turn the fuselage over on it's back and position the frontL.G.
wire(1/8" dia.)into theforwardlandinggear block. Be sure
itis centered fromsideto side. Positionthe rearlandinggear
wire— also 1/8"dia.— into therearL.G. block. Using the
plans forreference,fitthe rearwireto the forwardone at the
axlesand temporarilyhold inplace witha smallpieceoftape.
Now fitthe LOWER3/32" diameter cross-bracewireinplace
and correct asneeded forproper fit. Carefullywrapthe
three wirestogether at each axleas shown, with soft copper
wire.Solder thesejoints.
2. With the landing gear still in place on the fuselage, fit the
two 3/32" dia. top joiningwiresinplace as shown. Wrap the
jointscarefullywithwireand apply justenough solderto each
of the fourjointsto keep the wiresfromshifting.Carefully
removethe landinggearassembly from the fuselageand com-
plete the solderingofthesejoints.
3.Fit the top cross-bracewireinplace, directly over the lower
wire. They shouldline-upwhen viewingfromthe side. Wrap
thetwo jointsrequired with softwireand solder.
10

4.Clean-up each of the solderjointswith a wirebrush and make
sure that the jointsarestrong.Withthe 1/4"sheet provided,
make two inserts to fillthe trianglecreatedbythe frontand
rear main wires.Epoxythese in place, centeringthem on the
front and rear wires.When dry, sand them to shape usingthe
front and rearwires as the "leading and trailing" edges. Slip
your wheels in place and secure with wheel collars (not fur-
nished). Cut offthe excessaxlewireand exceptforcovering
thefillers, the landing gear isready for use.
5.Again place the landinggear assembly on the fuselage. Lo-
cate and drill1/16" guide holes forthe fourmetal landing
gear clips(seeplan forposition).Leave the landinggear in
position and make thetwo wing strutsupports as shownon
theplans fromthe materialprovided. Withthe tworearland-
ing gear clipsinposition, drillthe guide holes forthesesup-
ports. Removeallhardware fromthe fuselageand set aside
for final assembly.
FINAL ASSEMBLY
1.Remove bothW-1 (PLY)"cap" ribs from their sheet. Re-
move the four(4)holes stamped on theirsurface.AnX-acto
knifedoes thisbest. Accuratelytack-gluethese two ribsto-
gether. Use a sandingblock to "match" theiroutlines— they
must beidentical. Use a 1/4" dia. drillbit to "match" the
four holes. These too, must bethe same. Once satisfied,
separate the two ribs and clean off any dried glue with a
sanding block.
2.Tack-glue each W-1 (PLY) toeach side of the fuselage,
matching the top ofthe rib to the same edge as the cabin.
This must be accurateto insureproper wing/fuselagemat-
ing."Eyeball"the two holesat each end of the W-1(PLY)'s
to be sure that the 1/4" dowel holes you are about to drill
will clear F-10(PLY)and F-11(PLY) as shown on the plans.
Use an electricdrilland a 1/4" dia. bit to drillthe fourholes
into each fuselageside,usingthe W-1(PLY)'sas a template.
NOTE: drill these holesat right angles to the fuselage sides
andall the waythrough the inner F-17(PLY)'s.Use a pencil
to markthe leftW-1(PLY)"L" and the rightone "R". Re-
move them fromthe fuselage.
3.Cut two6-1/4"lengthsof 1/4"dia. dowel provided. Slightly
round theirends and insertthem inplacethrough the fuse-
lage. Center them as shownon theplans.Theseare thefor-
wardand aftwingpanel supportsand willNOT be epoxiedin
place until after the fuselage is covered. Leave them in place
for now forpositioningwingpanels.
4.Thread the outer nyrod tube through the wing ribs to just
inside the W-6 rib asshown on theplans. Leave the excess
stickingout ofthe root ribW-2.Epoxy these tubes inplace
on each rib. Make the "L-bend" linkageforthe inner nyrod
tube to connect the 90°bellcrank to the innerpushrod.
5. Drill holes for, and press in place, the wing strut blind mount-
ing nuts (No. 4-40 provided)into W-14A(PLY)and W-15A
(PLY),as shown on the plans.Drillholesfortheinterplane
strut eyeletsinthe W-13(PLY)'s.DO NOT glue eyeletsin
place until afterthe wings are covered.
6.Place the wingpanels on a FLATsurface,usingweights to
keep them that way.Epoxy the W-1(PLY)"cap" rib, that
you makred"L", to the leftwingpanel root, overthe nyrod
tube and flatagainstW-2 rib.Both the W-1(PLY)riband the
wing panel must beflatagainsta common surfaceforalign-
ment. Repeatthis stepwiththe right panel. When these
assemblies aredry,use the drilland 1/4" bit to drillallfour
holes inW-1(PLY)through the wingrootW-2/W-3(PLY)lam-
inate. Like the fuselage,drilltheseholes at accurate right
angles to the wingroot surface.
11
7.Slightly enlarge the hole inthe W-1(PLY)/W-2/W-3(PLY)
wing roots to accept the outerdiameter of the 1/4"-20 blind
mounting nut that will serve as the wing bolt attach point.
Epoxy thesenuts inplaceas shown on the plans. Keep epoxy
away from the threads, butuse enough to keep the nut from
coming loose.
8.Withthe1/16"balsasheet provided, cover the top center
section of each wing panel and allowto dry. Trim the excess
outer nyrod tube flush with W-1(PLY).
9.Join the two wingpanelstogetheron the worksurfaceusing
some scrap1/4"dia. dowels at the W-1(PLY)'sforalignment.
Usea sanding block to finalsand the leading edges to the
finished shape. Once satisfiedthat the panels havethe same
leading edge shape, sand the restofthe panels to finalshape,
including the wing tips.
10.Drillthe 1/16" guide holes ineach aileronhorn mounting
plate, W-19(PLY).Mount aileronhornswithNo. 2 screws
provided. Asshown on the plans, bend to correctlength and
install the aileronpushrod — provided— to the 90°aileron
bellcrank. Sincethe aileronshavenot yetbeen cut freefrom
the wing, neutral is easyto achieve.Turn the wingpanelsover
and epoxythe bellcranknut to the bellcranktray W-20 (PLY).
Removethe aileronhorns from the aileronsand set aside for
assembly aftercovering.
11.Carefullycut aileronsfreefrom wing at the inboard trailing
edge. Break freethe tack-glued joint between the aileron
spar and the aileronleading edge. Lightly sand the leading
edge of each aileronto the cross-sectionshown inSection
B-B on the plans,usinga flatsandingblock and medium
paper. Cut the hinge slotsineach wing panel and aileron and
trial-fit. The ailerons andpanels are now ready for covering.
12.The bottom door onthe right sideof the fuselagecan now be
cut free.Pin holes made from the inside at each corner of
thedoor between the 1/4"square frameswillmark it's lo-
cation accurately.Once the door is freefromthe fuselage,use
asandingblock to smooth it's edges. Set aside forcovering.
13.Remove the 1/4"spacer that isbetween the F-19 and F-21
pieces at the tailof the fuselage.When the fuselageand fin
are covered,removethe materialfromaround the stabilizer
slot and cut-awaythe smallpiece ofwoodat the tailpostto
facilitateinstallingthe stabilizer.The stabilizershouldbe
firstcoveredseparately,trial-fittedin placeand then havethe
fabricremoved fromthe center-sectionwhereitcontactsthe
upper F-21'sand lower F-19's to create a good glue joint.
Only then shouldit beglued in place. Thenthe coveredele-
vatorsarehinged to the stabilizerfollowedby hingeing the
coveredrudder overthe tailwheelsteeringwireto the fin.
14. The top and bottom access doors are meant to be fully func-
tional and provide access to the radio equipment as well as
the nylon 1/4"-20 wingattachbolts. Thereforeprovisionsfor
hingeing these doors as well as being able to "lock" them in
place should now beconsidered.On plan sheet No.2 we show
ascale-likemethod of being ableto open and lockthese two
doors. Thisis themethodwe used on our prototypeand it
workswell.We hinged ourdoors withregular model aircraft
hinges. Ifthis method does not appeal to you, we suggest
hingeing the doors withyellowSuper Monokotestripsand
using tape orTrimMonokote at the center to keep the doors
closed.
15. The aileron, rudder and elevatorservosshould now bein-
stalled.The installationshownon theplansis exactlywhat
we used on our prototypesandworksverywell.Installthe
rudder and elevatornyrodsas shown. Be suretoanchor the
outer nyrods inplace atvariouspoints inthe fuselageto pre-

vent "snaking". The location ofthe rudder and elevator
horns shouldbeestablished,the holesdrilledbut not installed
until aftercovering. The aileron servo should be first mounted
to the manufacturer'saileronservotray.The trayis then
mounted to a 1/16" plywoodplatethathasbeen cut to size.
The plateis then epoxiedinthe correctpositiontothe inside
roof of the cabin. The flexibleinner nyrodends thatconnect
the aileronsto the servocan accomodatevirtuallyany servo
type and output arm available. Make sure the servo installa-
tion workssmoothlybeforecovering.The throttleservois
installed after the plane iscovered and the engine installed.
STRUTS
IMPORTANT NOTE: THE WINGSTRUTSON YOURJ-3 CUB
AREFULLYFUNCTIONALANDAREABSOLUTELYRE-
QUIREDFOR FLIGHT. THEIRASSEMBLY, FIT ANDATTACH-
MENT ARECRITICAL.DO NOT DEVIATEFROM ANYOF
THE FOLLOWINGINSTRUCTIONS:
1.The wing struts provided (4) are 9/32" x 11/16"x 27" hard-
wood, preshaped. Verylittlesandingshouldberequiredto
smooth their surface.Extralength has been providedto allow
amistakeor two achievingthe correctangles. Bevelingthese
parts to fitflushwiththe bottom ofthe wingis important
and shouldbedone carefully.Note thatnone ofthe wing
strutsareinterchangeable.Theremust bea left-front,left-
rear, right-frontand right-rear.Inorder to avoidconfusionit
issuggested that you make a front andrear strut for one
panel, markthem assuch,set themaside and proceed to the
oppositeset.
2.Start byassembling the right and left wing panels to the fuse-
lage and securingwiththe 1/4"-20 nylon bolts provided. At-
tach the brassstrutplatesto the bottom ofthefuselageas
shown on theplans.Set the assembledairplaneupsidedown
on a flatsurface— linoleoum floorsworkwell— witha 1/4"
spacer between the top of the fuselageand the flatsurface.
This willimparta slight amount of dihedral to the wings as
in the full scale Cub.
3.As mentioned inNo.1 above, start with either the right or
left side, beginning with the FORWARDstrut. Prop up one
strut,on edge, directlyoverthe frontviewof the wing/strut
joint on plan sheet No.2.Remember thereis a left and right
strut. Using a razorsaw, carefullysawoffthe end of the
strut at the angle shown on the plans.Next, takethisstrut
over to your invertedmodel and, holding the cut angleagainst
the forwardoutboard strutplate, make surethatthe inboard
end of the strutis at approximatelythe rightlocationto en-
counter the brass strutplate. Note that the strutat this
point istoo long. Itwillbecut to length shortly.Ifthe
angleat the end of the strutis not quite right,use a sanding
block to bring it to true. Usinga 7/64" dia. drillbit, drill
the outboard strut-attachhole through the end of the strut
asshown on the plans, at a right angleto the bottom of the
wing.This holeis forclearanceof the No.4-40 machine
screwthatmounts the struttothe wing. Sliponeofthe
No.4-40 machine screwsprovidedthrough the hole you've
just drilledand into the blind mounting nutinthe wing.
Tighten this screwjust enough to create an impression of the
screwhead inthe wood. Removethe screw.Witha grinder,
knifeor sanding block, create a small "flat" around the hole
to allowthe head ofthe screwto sitflush to the wood when
inplace.As shown on the plans, epoxy one of the No.4
steel washers provided, to the strut, overthe attach-hole.
When dry,attach the strutto the wing.
4.The inboard endof the strut issimply cut tolenth as shown
on the plans. Removethe strut fromthe wing. With a 1/16"
dia.drill bit,drill the guide hole for theNo.2-56 x 1"
threadedstud thatis to betapped 1/2"into the inboard end
of the strut.Do not drillthishole any deeper than 9/16".
Tape off1/2"of the No.2-56 x 1"stud withmaskingtape,
dip the exposedend into 5-minute epoxyand "screw"this
end intothe holein the end of the struttothedepthof the
maskingtape. Plierscanbeused to hold the stud duringthis
operation. Wipe offany excessepoxy.Removetape and
allow to dry. Threadone of the clevises provided onto the
exposedend ofthe studand attachto the brassplate,in the
forwardhole. Reattachthe strutto the wingand fuselage
and proceed to make the rear strut. Followthe same pro-
cedure as above. Note that rearinboard end of the forward
strut must betrimmedas isshown on the planstoallowthe
rear strut to fitcloselyto it.
5.The "interplane" strutsaremade fromthe two pieces of
.072"dia. x 12"wireprovided.Theirshape is depictedon
plan sheetNo. 3, inSectionA-A.Note:do not bend these
to shape until the twonylonmounting clipsarefirstslipped
inplace with their ends facinginboard, towardthe fuselage
and flatagainst the frontand rear struts.The ends of the
interplatestrutfitinto the eyeletsprovidedinthe wing.Note
that inthe frontview,theinterplanestrutsexitthewingat
right anglesto the bottom ofthe wingand are held in place
bythe nylon fittings which are attached to the spars with the
No.2 x 1/4" wood screwsprovidedalso. The ends of these
strutsride freeinthe eyeletsforremoval.
6.We stronglyrecommend that you cover your struts with Fab-
rikote.Thiswillfurtherstrengthenthese strutsand, ifyou
areusingFabrikoteto coverthe rest ofyourCub, they will
becolorcoordinatedand ready to use. Ifyouareplanning
to use any other covering,we recommend thatyou fiberglass
thestruts andpaint to match.
COVERING AND FINISH
The full-scale J-3Cub isalmost completely fabric covered. This
coveringkept the weight down and added strength.Your Cub,
being an accuratescalemodel not justin outlinebut in construc-
tion sense as well, requires the same considerations. Top Flite's
FABRIKOTEis the perfectcoveringmaterialforyourCub. Itis
extremelylight, woven aircraftfabricthatis verystrongand is
pre-finishedand ready-to-use.The PIPERYELLOWcolorin
FABRIKOTEwillyielda perfectlyfinishedJ-3 PIPERCUB. On
plan sheet No. 1 you willfindthe Fabrikotecuttinglayout.Note
that thislayoutis approximateand yourcoveringtechniques may
increase or decreasesome ofthe dimensionsshown.
Allofthe individualpartsofour prototypeswerecoveredseparate-
ly; ailerons,doors,stabilizer,rudder,elevators,struts,wingpanels
and the fuselage.Onlyaftercoveringdid we hingethe surfaces,
add the windshieldand windows,the windowsupportdowels
(3/16" dia. provided), installthe cowlingand add any of the de-
tails.
The one piece cowlis matched tothe FabrikotePIPER YELLOW
color and requiresnoadditionalfinishing. If youwishto paint
thecowl we suggest using an epoxy-typepaint, color mixed to
match, afterfirstsandingwith No. 600 paper, wet. Note that we
have providedan accurate,correctscale3-viewdrawingof the 4
cylinder Lycomingengineused inmany ofthefullscaleCubs.
These detailscan be added usingplastic, metal, wood and a little
craftsmanship.
The 3-sheetsetof mylardecalswillcompleteyour Cub. The lo-
cation for thesedecals are called-outon the plan sheets.
Besure togive the firewall areaof the fuselagea liberal coat of
polyester resin or epoxyglueto fuelproof it and to sealthe nose.
Becarefulnot to get any resin or glue into the cowl mounting
block screw holes. 12

If,for any reason, you choose nottouse Fabrikote for covering
your Cub,we recommend thatyou use some kind of fabriccover-
ing,such as silkand dope. CLOTH COVERINGISRECOM-
MENDED ON THIS MODEL.
ENGINE AND COWL MOUNTING
1.Use a fewdrops of cyanoacrylateglue to mount your engine
temporarily to the motor mount, inthe approximateposition
shown on the plans. Turn the fuselageso that the firewallis
pointingstraightup.Settheengine andmount on thefirewall
about whereitis shown on the plans, exceptturnthe cy-
linder head of the engine so that itis invertedinstead of side-
mounted. Slip the cowl over the engine and on the fuselage.
On some types of engines, itmay benecessaryto remove the
needle valve.
Ifthe engine is sticking too far out of the cowl opening oris
notstickingout farenough, remove the cowl and reposition
the engine on the mount to correct.Once you have the
engine on the mount whereyou want it and the cowl down
over the nose ofthe fuselagewhereit willfinallyfit,remove
thecowland use the engine'sposition on the mountto mark
hole locationsformounting the engine to the motor mount.
Remove the engine.
2.The typical.40engine requires the use of No.4 x 5/8"sheet
metal screws(not furnished)to mount the engine to the
motor mount. Use a 3/32" dia. drillbit and accuratelydrill
themotor mount withfourguide holes. Next itwill be
necessary to pre-taptheseholes witha No.4 x 5/8" sheet
metal screw.Use some oilon the screw and intheholes to
assistinthe threadcutting.
3.Bolt themotor mount,without engine, inplace onthe fire-
wall. Ifyou areusing a muffler,attach itto the engine at this
time along with the needle valve, and anything else that
might be leftoff.Using the plansas a rough guide, CARE-
FULLY begin to cut-out the right side of the cowl.The use
of a hand held grinder is the quickestway to do this. En-
large thishole graduallyuntilyou can fityourenginethrough
the cowland setit on the motor mount whilethe cowl is
held in place withtape or byhand. Once you aresatisfied
that the hole is adequate and enough clearanceis leftaround
the engine, the edges of the cut-outcan becleaned-upand
smoothed with light sandpaper. Removethe cowl from the
fuselage.
4.Three (3) 1/2"x 1/2"x 1/2"hardwood cowl-mounting
blocks areprovided. These must now beepoxiedinplace on
thefirewallas shown on the plans. Differentengineset-ups
may require that these bemoved to other locations. This is
noproblem, as long as they roughly represent a triangular
mounting forthe cowl.Itis important that these blocksbe
epoxied in placeat the edge ofthe fuselagesidesat the fire-
wall. Too farinside the edge willallowthe mounting screws
todistort the cowl when they are tightened inplace.
Slip the cowlover the frontof the fuselageand then tempo-
rarilymount the engine withat least twoscrewsso that it is
flat againstthe mount arms. Position the cowl on the fuse-
lage so that itis properly clearingthe engine and drivewasher
and is square, both fromthe sideviewand the top view.Use
maskingtape to hold the cowl firmlyinposition.
Hold the nose ofthe fuselageto a light source, such as a bare
lightbulb and the mounting blocks can beclearlyseen thru
the light yellowplastic.Witha pencil, mark a holelocation
directly over each mounting block, inthe approximatecenter
of it.With a nail or other sharp object, mark and pre-punch
each of the three pencil markson the cowl.Witha 1/16" dia.
bit,drilleach of the three mounting holes through the cowl
13
and mounting blocks.Screw thethree No.2 x 1/2"cowl
mounting screws inplace and remove the tape holding the
cowl to the fuselage. Slipthe engine in place to besurethe
cowl is correctlyin place. Iftightening the cowlmounting
screws tends to forcethe cowl inward(distortion),that
particularmounting block should be shimmed witha scrap
piece of plywood to closethe gap.
5.With the cowl removed and the engine inplace, mark the
fuel line and throttlelineholes. Removethe engine and drill
these holes.
6.The throttle servo can now beinstalled inthe fuselage. The
location of this servocan varyas long as the access to itis
maintained and it's action does notinterfere with the fuel
lines or the tank itself.
7.The fuel tank andfuel lines should beinstalled carefully to
ensure correctfuel feed. The tankitselfshould besurrounded
byfoam rubber to keep itfrom "foaming" and to keepitin
placeon the tank tray.
PRE-FLIGHTADJUSTMENT AND RIGGING
Attach the wing panels and strutsto the fuselage. Itis NOT nec-
essary to overtightenthe wing bolts, justsnug them inplace.
With everythingattached, standback and viewthe airplanehead-
on.Ifone wingappears to below, adjust the strut clevises(both)
tocorrect.Once the wing panels appear the same and are square
with the stabilizer and rudder, proceed tothenext step (see
diagram below).
Now turn the airplaneso that you can viewit fromthe side.
Sight down the wingpanel facingyou to determine if the bottom
of the wing at thetip is on the same plane as the bottom ofthe
wing at the fuselage.Initially,you should adjust eitherthe for-
ward or rear strut(they act independently) to achievethe same
plane with boththe inboard andoutboard wing sections (see
diagram below).

Repeat this step on the opposite wingpanel.Once you aresatis-
fiedthatthe wingpanel are alignedproperlywithboththe fin
and stab and each other, "lock" all four strut clevises in place by
tightening the No.2-56 nut firmlyagainst the back of the clevises
as shown on the plans.DO NOT forgetto use smalllengthsof
fueltubingover each of the cleviseswhen they are inplace on your
airplane.Withoutthese fuelline lengths inplace, a cleviscould,
under high loads, become "unpinned", leaving the wingwithout
propersupport.
BALANCING
The C.G. range (Center ofGravity)shown on the plans isthe ideal
location.DO NOT exceed the rearwardlimitshownon the plans.
Our prototypesdid not requireany additionalweightsto achieve
correctbalance. Alwaysbalance your aircraft "dry". That is: all
equipment inplace, ready to fly,butWITHOUT fuel.
Forinitial flightsit is best if the airplaneisslightlynose heavy.
This condition keeps the airplane naturallystable with less chance
of stallingor snap-rolling.A slightlyforwardC.G. alsomakes the
controlssomewhat lesssensitiveand lessensthe chanceof over-
controlling.As flighttimeand familiaritybuild up, you may wish
tore-balanceyourCub witha more rearwardC.G. to increaseit's
acrobaticability.Do this gradually and check control response
at a good altitude.
ENGINE AND RADIO
The engine used inyour Cub should becompletely broken-in
and have the abilityto idle reliably.Be surethat your fueltank
is properlyinstalled and that the fuel lines are feedingproperly.
We have found that running the tank with "manifold pressure" —
apressuretap nipple, tapped into the mufflerwiththe overflow
fuelline connected to it — greatlyenhances fuelfeedat all atti-
tudes— the plane may gothrough — loops,rolls, etc.
Your radio installationshould beneat with all connections ab-
solutelysecure. Do not flywithoutfuellinesafetytubes over
clevises,as shown onthe plans. Set theaileron,elevatorand
rudder movements to those shown on the plans. Thesesurface
throws will give you positive control of the airplane without
making it over-sensitive. Later, when you are more familiar with
the airplane, these throws can bechanged to suit yourflying
style.
Your radio equipmentMUST bereliable.DONOT attempt to
fly with a radio that is suspect inany way.
FLYING
Ifyou area newcomer to radio control,we do not recommend
that you flyyourCub without the help ofan experiencedR/C
pilot. Hobby shops in your area can direct you to an organized
R/Cclub. Theseclubscan offerthe beginner much assistanceand
advice and theyusually have a flying site that is suitable for radio
controlledaircraft.
We would suggest that fortest flights, a calm day bechosen. Test
flyinginstrongwinds can bedone butitis more difficult.Al-
though the Cub canbeoperatedout of a relativelysmallarea, a
sanctioned R/Cflyingsite,withplentyofarea, freeofobstruc-
tions is much more desireable.YourCub can beflownoffeither
asphalt or a cut-grassfield.Hand launching an aircraftof this
size is not recommended.
With a fulltankand theengine idling reliably,point the plane
directlyinto the wind, advance the throttleslowlyand correct
for torque with a small amount of right rudder. The Cub should
beairbornein justa fewfeet.Don't let the nose come up too
sharplyand use both aileronand rudderto keep the wingslevel
during the climbout. Climbto a comfortablealtitudemakingall
turns gently.You will findthata medium throttlesettingon the
average .40engine is allthat is required fornormal flightspeeds.
Make alltrimadjustmentsat a good altitude. Use the transmitter
trim levers to obtain straightand level flight.
Once you are comfortable with the flyingcharacteristics, throttle
back, whilestillat altitudeand check stallbehavior.Itshould be
gentle and straightwithoutfallingoffon one wingor another.
Landingapproach is best done under about 1/4throttle (depend-
ing on windconditions),keepingthe wingslevel.Asyouapproach
the thresholdof therunway,you should beabout 10feetin the
air. Atthreshold,chop the throttletofullidle and settlethe air-
plane down gently on the main gear and allowthe airplane to roll
toa fullstop. The Cub by it's nature, has a great dealofparasitic
drag — struts,landinggear, wheels,wires,etc.Thisdragcanfool
you into makingoverlylong low throttleapproaches usuallyterm-
inating shortof the runway. Tryto remember to use a bit more
throttleon approach and withpracticespot landings of con-
siderable accuracycan bemade almosteverytime.
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