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Gas Powered Airplane Kits / FFP-03
Original Modelcraft Commando Construction Notes page 3
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page 3: Commando Construction Notes
run and linked to servos. Tubing has been sanded where it needs
to be CA'd in to prevent over-flexing.
Out of order, but triangles at exactly 90 degrees of angle made
of hardwood and with thick flat stock CA'd to them will assure that
the vertical stabilizer is at exactly 90 degrees perpendicular to
the horizontal stabilizer. The assembly is glued in with epoxy.
Epoxy, by the way, can be easily removed using a heat gun. When
the stuff bubbles, the parts release. Reversed the process, you
better be quick...it sets up fast. Of course, you can always use
Due to the narrowness (1 7/8 inches) of the fuselage, the rudder
servo and elevator servo had to be put in "back to back".
The rudder servo is on the left and the elevator on the right. The
tubing ran very well and after testing, only needed to be glued
and braced near the servos (small squares of balsa) and glue where
it exited the fuselage without any brace.
The antenna has been run. A small T-pin and some CA to hold it into
the vertical stabilizer has a rubber band looped over it for a shock
absorber. The fairing and hook are commonly found in hobby shops.
An access hatch is laid out and being drilled behind the landing
gear mount for easier extraction of the battery. 1/8 X 1/4 spruce
has been located inside and CA'd in place. The birch ply covering
is 1/32 inch and held down with #2 phillips button-head screws from
The battery is wrapped in air-conditioner filter (cheap, available,
and works well) and duct taped. What would we do without duct tape?
3/16 manufactured trailing edge is cut to size and laid in with
a steel rule to keep things nice and straight, then pinned in place.
A gap is left for the aileron which will be made from the same stock.
A piece of the 3/16 square stock is cut to run the length of the
trailing edge laid out on the plans and will take the aileron strip
hinges to be CA'd in. The wing root trailing edge and the corresponding
marked part of the 3/16 square stock are first grooved with a Carl
Goldberg centering tool and then routed out with a piece of brass
tube or wire and a round needle file finishes the job up smooth.
The aileron operating wire is bent to the redrawn plan shapes and
cut. Then I duplicate it and put it in a large coffee can "holding
bin" along with any other duplicated wing parts. Large coffee
cans are handy for that. I hate losing parts I duplicated.
The routed trailing edge has been laid back in and the 3/16 stock
glued in with the aileron wire inside. The 3/16 inch thickness would
not allow for any tubing for a wire guide! The wire was then pre-greased
with Vaseline. The 3/16 stock was CA'd in place on the top side
after careful checking to make sure everything was aligned perfectly
and pinned in place. The CA won't stick to the Vaseline, so the
wire is "trapped" inside the two wooden pieces. It works
like a champ! When finished building the wing I'll remove it,turn
it over, and the aileron root and 3/16 stock will be CA'd on the
other side The wing tips have been cut and matched and one glued
in with the wing spars. On this type of wing, the leading edge has
to be glued in last. Note the "Master Rib". This is for
duplication purposes and will be used LAST. If you don't copy from
a "master" each time, the size of duplicates constantly
grows. You can use the "master" to check that the next
pieces you make are indeed exact duplicates.
In building the wing, I decided to go with a flat surface or "asymmetrical"
wing for performance. Therefore, The wing ribs had to be cut "flat"
underneath. And, if you gotta do that...along with some other modifications
for the trailing AND the leading edge.......shucks...make a "Master"
and start cutting.
The first piece here is drawn from the "master rib" but
there are 7 other pieces of sheet behind it, the whole taped in
place with masking tape. You can see your lines through the tape!
The tape holds everything in place as you cut out the 7 pieces on
the scroll saw, or band saw if you have one. Retape when you finish
the first cut lengthwise to continue holding everything true. Then
repeat the process using a belt sander or sand by hand. Mass production!
Invest in a long piece of aluminum angle. It comes in so handy for
truing things up...like leading edges that are elevated where the
steel rule won't reach. When everything is lined up, hit the pieces
with CA. A master root rib has been cut out at left, but will not
be inserted until the center section is built and everything checked
for trueness, including the dihedral.
A view of the right wing. The aileron is placed in position but
not glued. The wing tip has been built up to receive Ultracote covering,
and a strip of 3/16 soft balsa shaped and glued to the rib next
to the wingtip, likewise to help in the covering process. Note the
1/32 stock pinned in place to check the fit. The leading edge top
and bottom will be covered with 1/32 back to the first spar to add
strength by forming a D shape. The trailing edge has a 3/8 inch
wide 3/16 strip to reinforce it. The plans call for 3/16, but that's
for free flight. 3/16 would not be enough for the greater stress
of radio control.
The left wing construction has begun. The leading edge stock is
NOT glued in yet. The aluminum angle assures the wing leading edge
will be true. The steel rule likewise assures the trueness of the
trailing edge. The rib near the wing has just been glued in and
is braced by two homemade 90 degree angles of hardwood.
The left wing is framed up and all the ribs are in. The ribs should
be put in FIRST and made true with the aluminum angle and shop rule.
The false ribs or riblets if you barbecue, can then be made and
"fine tuned" by sanding. Doing it this way produces a
true wing. Notice all the homemade 90 degree hardwood angles. Homemade
jigs are well worth the time. Including very small ones as you see
next to the false rib or riblet being inserted. It was made especially
to get between the leading edge and the main spar.
Three views of how to check the trueness of a wing BEFORE YOU GLUE.
Use aluminum angle. And if your angle is not tall enough...go buy
taller angle...or block up what you have with nice, true lumber.
Alignment is so much easier with a nice, straight line. I could
only wish I had longer angle for this wing so it stretched beyond
the wingtip. But, if the separate pieces are trued, the shortness
of the angle or ruler is overcome by previous work.
The wing will be held to the fuselage using 2-56 bolts. Two in the
back and one in the front. The back is shown here, glued in with
epoxy and clamped with cheap Chinese-made clamps...and they come
in very handy for modeling. Epoxy is neat stuff not only for the
strength of the bond, but because if I've miscalculated, a heat
gun is going to loosen the epoxy right up and I get to "rethink
my position" and reglue without difficulty.
Great Plains 2-56 socket heat bolts are fitted to blind nuts CA'd
in under the 3/16 ply in the cabin. I will then CA the washers to
the plywood inside the wing and "box in" the washers and
bolt holes with balsa.
After cutting out and trying the 1/16 sheet balsa covering, I marked
it for drilling an access hole to insert and remove the socket head
A spiral-wrapped sheet of medium grade sandpaper makes a fine reamer.
The plastic soda straw next to it will be inserted and lined up
over the washer. That way you don't lose the bolt and it is self-aligning
to a certain degree.
Two pieces of balsa have been drilled to the size of the washer.
One is CA'd in place. The other is being sanded to fit. When covered
with the rest of the 1/16 sheet covering, the should give access
to the 2-56 bolts and prevent losing them inside the wing center
Right wing underside has 1/32 sheet balsa installed. Left wing underside
is ready, and the balsa has been measured and cut ready to try the
photos at different angles showing wing leading edge covered in
a "D" shape with 1/32 balsa sheet back to the main spar
for more strength required flying radio control.
I found that the mounting bolts I installed interfered
with the operation of the ailerons, so I made a change in the mounting
bolt system, moving it farther back on the trailing edge. It is
noted below in 001 and should be substituted for the photos and
text where I explain first installing them, and the image and text
for 001 below should be substituted.
After centering the leading edge of the wing and
installing the front 2-56 socket head bolt and blind nut, the trailing
edge is taped in place and the distance from a specific point on
the trailing edge to a specific point on the wing is measured and
adjusted for BOTH right and left sides of the wing until the distance
is exactly equal. I used the tip of the balsa trailing edge of the
horizontal stabilizer where the elevator is joined and the inside
corner of the wingtip's trailing edge. This is where exact duplication
pays off. When the distances were equal, the exact center of fuselage
and wing were marked. The wing was taped with masking tape and first
hole drilled, the blind nut installed, then the second hole drilled
and blind nut installed. I installed a 1/16 strip of plywood over
the cabin trailing edge to reinforce for the mounting bolts.
Hinge locations on both ailerons have been marked
and slots cut. The aileron wire rods from the servos have been located,
marked and drilled. The wafers have been inserted and the ailerons
test-fitted but NOT CA'd YET. The wing and ailerons must be covered
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Balsa Model Airplane Kit, Balsa flies better.