Here is the fiberglassed and assembled airframe
ready for primer. Super Fil is used for fillets.
The pickup, vent, and overflow tubes stop just inside the tank. With this
design, it is unnecessary to cap the overflow for flight.
Assemble the two main parts of the tank with the outboard
portion of the tank’s body fitted inside the inboard portion.
Using a few strips of masking tape to hold it in place, solder
the tank body together.
Study the plans and photos so you understand the tube
arrangement on the tank, then bend and install the 1/8-inch
copper tubes. All tubes stop just inside of the tank. The fuel
pickup should point toward the fuel shutoff. The filler tube
pokes into the front of the tank and should clear the top of the
fuselage when installed.
Consult with your pit person about how he or she would
like the filler tube pointed: up, forward, inboard, etc. The
overflow goes from the top outboard corner of the tank and
“snuggles in” behind the filler tube. It should be cut off so
that any fuel overflow is discharged down and away from the
model. The fill tube and overflow tube are wrapped together
with a few turns of soft wire and soldered for extra strength in
the event the aircraft flips over.
After the tank is finished, solder it to the mounting plate and
check the tank for leaks. Connect the fill tube and vent with a
short piece of fuel line, then connect a bulb or syringe to the
pickup tube. Pump air into the tank, immerse it in water, and
look for bubbles, which indicate leaks.
Solder any leaks and repeat the procedure until the tank is
leak free. Fill the tank roughly half full of dope thinner and
swish it around to remove any soldering residue. Drill 3/32-inch
mounting holes in the tank, and matching pilot holes in the
Make the fairing from a soft balsa block or laminate some
scraps of 3/8-inch balsa. Before installing the fairing, cover it
with fiberglass cloth and finishing resin. When it’s dry, sand it
smooth and install. To get a perfect fit between the tank and
fairing, liberally coat the front of the fairing with 5-minute
epoxy and microballoons then install the tank with a wax
paper barrier between the tank and the fairing.
Remove the tank when the epoxy is dry, and sand to final
shape. Super Fil or epoxy/microballoon fillets can be installed
on the wing and tail joints and sanded smooth when dry.
Sandpaper wrapped around various sizes of fuel tubing makes
a great sanding tool.
Now the airplane is ready for primer. If you have a
favorite finishing method, by all means use it. Otherwise,
here is mine.
MJ 3 Model Aviation JUNE 2015 www.ModelAviation.com