Spa3D - SPAD To The Bone

Building Instructions/Essay
Design and instructions by Dean "Tattoo" Tuinstra
Simple Cheap Fun-Fly 3D design
Engine--.46-.47 (GMS .47 used on prototype)
Length--36" (length of "rail" fuselage not including engine and rudder)
Weight--4 ½ pounds (approx)
Channels--Aileron, Rudder, Elevator, Throttle
Materials (represents exact materials used on prototype)
__4mm Coroplast (local sign shop, Harbor Sales, Regal Plastics, convenience store or gas
station dumpster...ask first!!!)
__Aluminum "U" Channel (1/16" thick x ½" x ¾" x ½" I.D.) (Lowes) 36" needed for fuselage (
sometimes called ¾" plywood end cap)
__Poly Kitchen Cutting board (Wal-Mart, American Chef brand used on prototype) For
engine mount
__PVC Gutter Pipe (2 ½" O.D. from ACE Hardware used on prototype) For control horns,
back plates, doublers
__Aluminum Stock (1" wide x 1/8" thick from Lowes) 20" piece needed for landing gear
__#6 x ¾" long self tapping screws (Lowes) for engine, mount and landing gear mounting
__#6 x ½" long self tapping screws (Lowes) for wing, tail and profile fuselage mounting
__Deck screw 1 ¼" long (scrounged from garage, one used for wing attachment)
__6-32 x 1 ½" long bolts and nuts for wheel axles (2 bolts, 4 nuts)
__5/32 music wire (hobby store) for wing supports (one 36" piece will be cut into two 18"
__.078 music wire (hobby store) for tail wheel wire and pushrods
__2-56 Threaded pushrods with metal clevises (From hobby store, used on ailerons)
__Regular sized zip-ties and small zip-ties (Dollar General, Wal-Mart, or any home
improvement or auto parts store)
__Double sided foam mounting tape (from Wal-Mart hardware department)
__Great planes 10 ounce fuel tank and fuel line (hobby store)
__2" diameter lightweight foamy wheels (From hobby store, two for main gear)
__1 ½" diameter lightweight foamy wheel (From hobby store, one for tail wheel)
__Your engine
__Your radio
__Tools--Normal hand tools, sharp hobby knife & straight edge, hacksaw and drill with 1/16"
bit and up a must. Tin snips (sheet metal shears) helpful. If you don't have a band saw, find
someone who does for cutting out engine mount.
Note: These instructions represent how I built my SPA3D, what I used, and the exact order in
which I built it. This design is wide open to personal preferences, modifications, and further
experiments. If you build yours like mine, you will have a good flying airplane...but nothing is
perfect and you may have better ideas! Please never hesitate to try them! These planes are
far from rocket science and exact screw locations throughout the design are not critical, just
put them where you think they will be the most effective, according to the general locations
shown in the drawings and reference photos. This design is also easily modified to
accommodate different engine sizes by simply changing the wing span and fuselage length,
with all other dimensions staying the same. For a BB .46 or .47, build as represented here.
For a strong .30 class engine or bushing .40 to .46 build with a 34" span x 34" fuselage rail.
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For a strong .20-.30 sized engine build with a 32" span x 32" fuselage rail. 1. ENGINE MOUNT. I started by cutting out the engine mount. It is made from a POLY
kitchen cutting board I bought at Wal-Mart. There are several different brands, and they are
usually around 7/16" to ½" thick. It is VERY important that what you get says POLY on the
label so that you know its high density material. It should be milky white in appearance and
slightly see through. The brand name I use is "American Chef". One brand name to stay
away from is "Fiberware" as it does not say Poly on the label and is made from recycled
"particle plastic" and is brittle and breaks easier. I cut mine out on a band saw. You must go
slow or the plastic has a tendency to melt back together behind the blade. Be patient, this is
the hardest part of building this airplane. Start by cutting out the 3" x 5" piece. Then use your
engine and throttle servo to mark for their respective cutouts. MAKE SURE YOU LEAVE 1"
Making the rectangular cut-outs can be a little tricky. I like to cut both sides first and then
make a diagonal cut to take out a "triangle" of material. Using several opposite passes of this
method and you can get in there to finish your cut-outs.
2. ENGINE ASSEMBLY. Next I installed my engine (GMS .47) and throttle servo to the
engine mount. I used a 1/16" drill bit to pilot drill for the servo screws and then mount the
throttle servo with standard servo screws. I used a 3/32" drill bit to pilot drill for the engine
screws, and then mounted the engine with #6 x ¾" self tapping screws (bought at Lowes).
Next I plugged the throttle servo and a battery into my Rx and rigged my throttle using a .078
diameter music wire (bought at the Hobby Shop) pushrod. Next I installed the muffler to the
engine to finish out this assembly.
3. ALUMINUM FUSELAGE. Next I cut (hacksaw) a 36" piece of 1/16" thick x ½" x ¾" x
½" I.D. (inside diameter) aluminum "U" channel for the fuselage rail. I bought this at Lowes
(comes in 8' lengths) and it's marketed as "3/4" plywood end cap". Next I mounted my engine
assembly to it using two #6 x ¾" self tapping screws. Center the rail behind the engine, on
top of the engine mount, with the end of aluminum flush with the back of the engine cut-out
and MAKE SURE the aluminum doesn't touch the back of the engine. Drill the aluminum
holes large enough for the screws to pass through, but it's good to have a tight tolerance
here. I used a 1/16" drill bit to pilot drill the mount for the screws...this makes them nice and
tight, and the POLY can take it, so don't worry. The strategy I use here is to drill the holes in
the rail first, then pilot drill for, and install the forward screw. Now I can tweak the mount to
get it perfectly straight and then pilot drill and install the rear screw. Exact screw location is
not critical, just make sure you don't put the rear screw in the rear 1" area of the mount. If
you do, the tip of the screw that pokes out of the bottom of the mount will interfere with
landing gear mounting. 4. LANDING GEAR . For my landing gear I cut (hacksaw) a 20" piece of 1/8" thick x 1"
wide aluminum stock I bought at LOWES. It bends easier than you think and can easily be
formed in a vise. I used 2" lightweight foamy wheels I bought at the hobby shop. For axles I
used 6-32 x 1 ½" long bolts with two nuts each. Just stick the bolt through the wheel, put a
nut on up to the wheel, install to the gear, and put the other nut on good and tight. I installed
my landing gear to the bottom of the engine mount, behind the throttle servo, using two #6 x
¾" self tapping screws. Again, you want close tolerance holes in the landing gear and I pilot
drilled the mount with a 1/16" drill bit so the screws are good and tight.
5. WING. Next I cut out a 36" x 24" piece of 4mm Coroplast for my wing. Make sure the
flutes are running the 36" direction. Measure 5" from the top, this is your first leading edge
fold flute. I used a #1 phillips screwdriver to run along (cave in) the inside of the flute so that it
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will fold. Do the same for a total of five flutes (where you started and four more above it). The
Coroplast may try to fight you here, but keep at it until you have a fairly rounded leading
edge. You can now cut out the 7/8" square leading edge fuselage hole, and the 7/8" x 4" long
fuselage slot starting 6" behind the lowest leading edge flute. When I cut these holes out I
like to error slightly on the small side so I have to slightly force the fuselage through the holes
for a nice tight fit. Now cut out the 2" x 4" section between the ailerons. I usually don't hinge
the ailerons until later, because I don't like them flopping all around while I'm working on the
rest of the plane. Before putting the wing on the fuselage, I drove two 18" pieces of 5/32"
music wire (from the hobby shop) into the wing. One is in the flute directly in front of the
aileron hinge and the other is in the flute at the front of the 4" long fuselage slot (or 6" behind
the lowest leading edge flute). For future reference, this forward piece of music wire is also at
the airplanes CG. I found the music wire very hard to slide into the flutes. Using a file, I
beveled one end slightly, and then ended up spraying them with Windex and then tapping
them in with a hammer, with the wing resting sideways on the floor. I found some scrap 1/8"
music wire in my shop to use as a drift to get them centered in the wing.
6. WING ATTACHMENT. Now it's time to slide the wing on to the fuselage like a
shiskabob. Once you get the fuselage slid through the wing leading edge hole and fuselage
slot, slide the wing all the way up to the engine mount. I then cut (tin snips or sheet metal
sheers work great for this) out three ¾" square pieces of PVC from gutter pipe (two for the
front screw and one for the back screw). I use 2 ½" square O.D. gutter pipe I bought at a
local ACE Hardware store. In two of these I drilled a 1/16" pilot hole for screws to tap into,
and in one I drilled a hole big enough for a #6 screw to go through. You want to mount the
wing in the front (screw goes all the way through the wing top/PVC piece/fuselage/bottom of
the wing/taps into PVC piece) and in the rear, through the fuselage and through the flute just
forward of the rear piece of music wire and taps into a PVC piece. I used a #6 x ½" self
tapping screw for the rear mount point. I didn't have a #6 screw long enough for the front
mount point, so I went scrounging around the garage and found a 1 ¼" long deck screw that
worked perfect. Install the forward screw so that it catches the second to the last (rearward or
aft) flute in the lower wing folded over section (you want it far enough back so that it won't
interfere with fuel tank installation). Tighten the screws just to the point that you see the
Coroplast start to crush in slightly and that's enough. Make two "U" shaped wing tip supports
out of coat hanger. Start with a 4" piece of hanger and bent it into a "U" so that the inside
dimension of the "U" is ½" wide. Now double over each leg of the support so that it's a tight
fit into the flutes. Insert these into the last (furthest aft) flute of the bottom wing folded over
section, and top wing flute directly above it, at the wing tips. 7. HORIZONTAL STAB/ELEVATOR. I cut my Horizontal stab/elevator from a 16" x 8"
piece of 4mm Coroplast with the flutes going in the 16" direction. I gave the stab a 2" taper
and hinged it at 4" (see plans drawing) by cutting away the bottom side of the hinge line flute.
I then cut out two ¾" square pieces of PVC and drilled a 1/16" hole in them for the screws to
tap into. The Horizontal stab/elevator is mounted to the bottom of the fuselage with two #6 x
½" self tapping screws through the fuselage/stab/tap into PVC piece. Make sure the elevator
hinge is clear of the end of the fuselage, and that it is mounted straight and centered. I drill
the screw holes (close tolerance but large enough for the screws to pass through) in the aluminum fuselage first and then I like to install one screw, and then tweak the stab until it is
lined up perfectly straight, and then install the other screw. Tighten the screws through the
fuselage/Coroplast/tap into PVC piece, until the Coroplast just starts to crush slightly and
that's enough.
8. VERTICAL STAB/RUDDER. I cut my vertical stab/rudder from an 8" x 8" piece of
4mm Coroplast. I gave the stab a 2" taper and hinged it at 4" by cutting away one side of the
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hinge line flute. Cut the bottom ½" of the rudder away (so that it will clear the rail). I was
going to leave the rudder squared away at the bottom, but it ended up hitting the elevator
control horn, so I trimmed a 2" x 2" triangle off the lower rear corner (see plans drawing). Cut
out two ¾" square PVC pieces and drill with a 1/16" drill bit for screw tapping. The vertical
stab/rudder will be mounted to the inside of the aluminum fuselage with two #6 x ½" self
tapping screws just like you did the horizontal stab/elevator. It really doesn't matter what side
you mount it to, but I like to mount mine on the left side to offset muffler weight (however
slight that may be).You will notice that I mounted the vertical stab/rudder with the rudder
hinge line 2" forward of the aft end of the fuselage, simply because I think it looks cool and
gives better elevator/rudder clearance. Before mounting the vertical stab/rudder to your
plane, you will want to install the tail wheel wire into the rudder! I used .078 music wire
(hobby shop) and started with an 8" piece. Using needle nose pliers, bend a 2" "L" in the
wire. You will now poke (solid pressure is all it takes to poke it through the flutes) this into
your rudder so that the 2" leg goes into the rudder, 1 ½" above the bottom edge of the
rudder, and the 6" leg runs inside the hinge, and out the bottom of the vertical stab/rudder.
Using the vertical stab/rudder/tail wheel wire assembly as a guide, you need to figure out
where you need to drill the tail wheel wire hole in the bottom of the fuselage. I used a 3/32"
drill bit for this which is slightly larger than the .078 music wire. Drill the tail wheel wire hole in
the bottom of the will also run through the horizontal stab Coroplast. You can
now slide the tail wheel wire through the fuselage hole and position the vertical stab/rudder in
place on your airplane, drill for, and install it with the #6 x ½" self tapping screws into the ¾"
square PVC pieces. A helpful hint here for positioning the vertical stab mounting screws is to
drill the holes in the aluminum close to the top edge of the rail. Once the vertical stab/rudder
is installed, you can finish out the tail wheel. I used a 1 ½" diameter foamy wheel I bought
from the hobby store. I have found that lightweight foamy wheels sold as electric main gears,
work great as tail wheels! I used needle nose pliers to bend an "L" in the bottom of the wire,
slipped the tail wheel on, and finished it out with another "L" bend to keep the wheel in place.
I guess you could call the finished tail wheel installation a "J" bend. My tail wheel hole was
too small for the music wire, so I drilled it out to 3/32" to slide on and spin freely.
9. CONTROL HORNS. If you haven't done it already, hinge your ailerons by cutting away
the bottom of the aileron hinge flute. I made my control horns from the angled portion of PVC
gutter pipe. I used 2 ½" O.D. gutter pipe I bought from a local ACE Hardware store. Tin Snips
(or sheet metal shears) work great for cutting them out. Make four control horns and four
control horn back plates. I made the horns 1" high x 1 ½" long x ¾" wide base. The back
plates are ¾" wide x 1 ½" long. I used two #6 x ½" self tapping screws for mounting each
control horn. The control horns are drilled out close tolerance for the screws and the back
plates are pilot drilled with a 3/32" drill bit for the screws to tap into. A helpful hint here it to
use a couple drops of CA glue to tack the control horns onto the control surfaces while
installing the screws. Make sure you angle the aileron control horns inward slightly to line up
better with the aileron servo arm. Install the rudder control horn so that the screws pass
through the rudder Coroplast just above the tail wheel wire...this will give the tail wheel wire
maximum support for taxiing and landing. Install the elevator horn far enough from center so
that it will not interfere with rudder operation. Make sure the control horns are as close to
the hinges as comfortably possible. Tighten screws until the Coroplast starts to slightly crush
and that's enough. Drill each control horn for the size of pushrod/clevis you are going to use.
I drilled my control horn clevis holes ¾" from the base of the horn.
10. RECEIVER AND BATTERY INSTALLATION. I simply wrapped my receiver and
battery in foam and zip-tied them to the aluminum fuselage under the wing. I found zip-ties at
a local Dollar General Store (a bag full for...a dollar) I put the battery in front of the receiver
for the simple reason that if I crash hard enough to break the zip-ties, the battery won't take
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the receiver out. Also, with the receiver aft of the battery, there is a better chance of all the
servo leads reaching it. For antenna routing I poked a hole in the bottom of a wing flute (with
a small drill bit) and ran it down the flute and out the wing tip. I used a scrap servo arm as a
"keeper" on the antenna near the Rx. I put a small piece of fuel tubing on the portion of
antenna that exits the wing tip, then inserted the antenna back into another wing flute near
the wing trailing edge and used the fuel tube crammed in the flute as a "stopper" to keep the
antenna from pulling out. I mounted the switch where covenant, near the center, on the left
side of the wing. I used a pointed Exacto knife to cut the switch hole in the Coroplast and a
3/32" drill bit for the switch plate screw holes in the Coroplast. Tighten switch plate screws
until the Coroplast starts to slightly crush and that's enough.
11. FUEL TANK INSTALLATION. I used a Great Planes 10 ounce tank (hobby store)
and mounted it on top of the wing. I mounted it in this location to get it as close to the CG as
comfortably possible. Before mounting the tank, make two tank mounting zip-tie doublers
made from PVC gutter pipe. I made mine ¾" wide x 3" long. Clean the Coroplast in the tank
mount area and the PVC tank mount doublers with Windex (generic brands are cheaper at
Dollar General) and glue the doublers to the top of the wing (I used dots of Medium CA).
Using a drill bit the size of your zip-ties, drill a hole at each outboard end of the tank mount
doublers. Make sure these holes line up with a wing Coroplast flute! Drill the holes so that
they go through the PVC AND ONLY THE TOP of the Coroplast flute! It will take four zip-ties
to mount the tank. Now take one zip-tie and pre-curl the tip of it. If you do this right, you can
push the zip-tie into one hole and it will run through the Coroplast flute and poke out the
other hole. Pre-position a zip-tie in each tank mount doubler in this manner. Next I used
double sided foam mounting tape (Hardware department at Wal-Mart) between the tank
mount doublers and fuel tank to stick the tank to the wing. Once the tank is in place, insert a
second zip-tie into each of the zip-ties already in position and cinch them down around the
tank. Make sure the zip-ties are tight enough to not vibrate on the tank, but not too tight to
distort the shape of the tank. Now you can connect your fuel lines (hobby store) from the tank
to the engine's carb and muffler.
12. PROPELLER AND SPINNER. If you haven't already, install your propeller and
spinner. I used a Du-Bro ¼-28 spinner nut and a MAS 11x6 prop for the first several flights
and then switched to a MAS 12x4 for better hover power.
13. SERVO INSTALLATION. At this point, everything on your plane should be done
with the exception of servo installation and the profile fuselage installation. I found that the
addition of the profile fuselage was negligible in it's effect on the airplane's weight and
balance (less than a flute), so I installed the servos and completely balanced and rigged my
plane to flight ready condition at this point, before installing the profile fuselage. You will now
install your aileron, elevator, and rudder servos into your aluminum fuselage. POSITION
THEM TO ACHIEVE PROPER CG. The CG of your plane with THE TANK EMPTY is 6" from
the leading edge, or simply the wing flute you inserted the forward piece of 5/32" music wire
into. While determining your airplanes balance, don't forget to include the weight of the
pushrods you will use. Make sure the aileron servo is far enough forward of the ailerons to
insure smooth aileron operation (too close and the downward pushrod angle may get too
severe). Once you are satisfied of the servo locations, push the servos down into the bottom
of the aluminum channel. Tolerance is very close here, and varies between servo brands
and aluminum brands. Sometimes the channel must be spread slightly to insert the servo. If
your servos go in real nice and tight, simply wrap a zip-tie around them and the aluminum,
cinch them down and your done. If your servos are not tight, or slide right in nice and easy,
then you will have to use double sided foam mounting tape between the bottom of the servos
and the aluminum to stick them down, then secure with zip-ties. When wrapping the aileron
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servo zip-tie around the aluminum fuselage, simply poke a hole (use a drill bit) in the top (top
of flute only!) of the Coroplast flute on each side of the aluminum. Curl the tip of the zip-tie. If
you do it right, it will go in one hole, down the flute, and come out the other hole on the other
side of the fuselage. A helpful hint here is to be careful of where the zip-tie ends are, make
sure they will not interfere with the servo arm operation. You can now plug your servos into
the receiver. I routed my servo leads around the trailing edge of the wing in the center and
then along the bottom of the wing. I bought some really small zip-ties at the Dollar General
store that make perfect wire ties. I drilled a small hole in the side of the aluminum fuselage
as a servo lead zip-tie location. You can also poke two small holes anywhere in the
Coroplast you want to and use the small zip-ties to secure your wire leads. Once done, if you
haven't already, you can trim the excess zip-tie ends from all the zip-ties on your plane. 14. RIGGING. If you haven't already, rig your throttle. I used a .078 music wire pushrod for
this. I used z-bends at both ends with a zig-zag (slight z-bend) in the middle for adjustments.
For my ailerons I used 2-56 threaded pushrods with metal clevises (hobby store). Whenever
using clevises, make sure and use a small piece of fuel tubing around them for extra
security. For my elevator and rudder pushrods I used .078 music wire. I used z-bends at both
ends with a very very very mild low angle zig-zag (mild Z-bend, more like ~) in the middle for
adjustments. Rig the rudder and elevator straight away for neutral. Rig the ailerons
PARALLEL TO THE FUSELAGE for neutral. Use the furthest outboard holes in your servo
arms to give your control surfaces barn door travel (I've never even measured mine, so don't
ask me what the travels answer would be much as possible!). Make sure
your tail wheel is parallel to your rudder for straight tracking while taxiing and take off.
CONGRATULATIONS! Your airplane is now flight ready and you could go fly it if you wanted
to. 15. PROFILE FUSELAGE . Adding the profile fuselage will give you a small amount of
added stability, but for the most part it's strictly for looks. I started with a 5 ½" wide x 23" long
piece of 4mm Coroplast with the flutes going the 5 ½" direction. I simply laid it on top of my
plane and started trimming it to fit my plane. I started by measuring for the lower front notch
(depth x distance to the tank) and cut it out. Then, with the piece laid on its side on the plane,
I marked for the location of the servos. I used a spare servo to mark for the servo height and
made the servo cut-outs. I then positioned it in place on the airplane with the aft end
overlapping the vertical stab and marked the aft angle with a pencil. I cut the aft side to
shape and the piece now fit my airplane. For the top profile contour I simply used my
imagination. I chose a very simple, straight cut, sloping fuselage shape and I think it looks
pretty cool. I made the front start at the height of the fuel tank and tapered the rear to what I
thought looked about right. Be creative here! You can make the profile fuselage any shape
you want. Once satisfied, I installed the profile fuselage to the aluminum in the same manner
as the vertical stab with #6 x ½" self tapping screws and ¾" square PVC pieces for the
screws to tap into. I used one screw under the wing in the front, one forward of the aileron
servo, and one aft of the elevator servo. I used a small wood skewer in the Coroplast flutes
to lock the rear of the profile fuselage to the vertical stab. I made it from a scrap piece of
yardstick cut to the size of a flute. Now all you need to do is deck out your SPA3D with a
bunch of cool stickers and trim...AND YOU'RE READY TO ROCK!!!
16. FLYING. Make sure you follow all AMA safety guidelines. If at this point you have any
questions regarding the preparing, rigging, starting, running, radio range checking, field rules,
trimming and flying of an R/C aircraft...YOU ARE NOT READY TO FLY THIS AIRPLANE.
Please get the help of an experienced R/C pilot or local R/C club. The SPA3D will take off
after a very short take off run. In flight it should be stable and predictable. You will notice that
high G maneuvers at higher speeds will cause the wing to visibly flex, this is normal, but
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please use caution and common sense along with your throttle. I have flown mine all out, but
I also don't do anything stupid just to "see what she can take" is not worth the
consequences if something goes wrong. Although this plane will fly at full throttle, its main
purpose is having plenty of power for 3D maneuvers. Hovering is straight forward and the
most stable hovering Spad yet. Mine hovers at half throttle with the GMS .47. Flat spins
using only elevator and rudder are phenomenal, and using slight opposite aileron will even
flatten them out even more. If you like upright flat spins...wait until you try an inverted flat
spin! Wow! Awesome harriers, inverted harriers, toilet bowls, waterfalls, and most other FunFly maneuvers are not only possible but very sweet, so much so that the SPA3D has been
identified by many Fun-Fly pilots as the best 3D trainer around, especially when cost,
simplicity and EDF (Emotional Debt Factor) are factored in. Have fun, and if you have any
questions, please visit any of several Spad forums as linked to from the Spad Home Page at [S.P.A.D.] [SPAD Index] [SPA3D] [Page2] [Page3] [Page4]
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