.
Like most SIG kits, the fuel tank in this model is installed from the rear of the fuel
tank compartment rather than through a removable hatch. This choice was made
for several reasons. A hatch opening makes the nose weaker and it's very
difficult to keep oil from leaking in around a hatch.
BUILDER'S TIP:
Here's a handy trick that you can use
on any model without a fuel tank hatch.
Make a "pull tab" on the back of the
tank using fiber-reinforced strapping
tape. Now you'll have something to
grab if you ever need to remove the
tank.
A method of fastening the hatch must
be built into the fuselage, adding to the
complexity and construction time of the
model. Besides, modern plastic fuel
tanks are virtually indestructible under
normal use when installed properly, so
they seldom need to be removed for
maintenance.
A 16 oz. to 20 oz. fuel tank is recommended for the FOUR-STAR 120. The
Sullivan 16 oz. slant tank fits well, as do the DuBro 16 oz. and 20 oz. tanks. Most
engines will require the tank to be mounted as high as possible in the fuselage.
Use foam rubber under the fuel tank as necessary to position it properly.
Radio Installation
Screw the nylon control horns onto the rudder and elevator as shown on the
plans, then re-install the inner nylon push rods that you prepared in step 58.
Snap a 4-40 R/C link onto the rudder horn, then cut off the excess nylon tubing,
leaving a 1/8" gap between the end of the tubing and the R/C link. Cut a 4-40 x
8" threaded rod to an overall length of 5-1/2", measuring from the threaded end.
Install the threaded rod in the nylon tubing, smooth end first, so that
approximately 5/8" of the threaded portion remains exposed. (The metal rod will
help prevent the nylon tubing from buckling under flight loads.) Thread a 4-40
hex nut and the R/C link onto the end of the pushrod until the rudder is in neutral.
Tighten the hex nut against the clevis to help reduce any "slop" in the linkage.
Repeat this procedure for the elevator push rod, this time cutting the threaded
rod to an overall length of 4-1/2".
If you look closely at the photo, you should be able to see that a short length of fuel tubing has been slipped over the R/C
link. The purpose of this is to keep the link from popping open during flight, which could cause a loss of control. For safety,
install fuel tubing "keepers" on ALL of your R/C links and solder clevises. Without them, your model probably won't pass the
standard safety inspection performed at most fly-ins.
Hook up the ailerons by installing control horns and the aileron push rods. The servo leads will probably require short
extensions to reach the center "V" harness which is required to connect the servos to the receiver. Radio manufacturers
generally have these items available as stock equipment. It's best to keep the extensions as short as possible since
excessively long wires have been known to cause radio "glitches" under certain conditions.
Use the die-cut lite-ply Aileron
Positioning Guide (APG) to set the
ailerons at neutral. Adjust the R/C link
on each aileron push rod until the APG
seats perfectly against the bottom of
both the wing and aileron.
A typical radio installation is shown in
the photo. Always wrap your receiver
and battery in foam rubber and position
them forward of the servos. If you use a
lightweight engine, you may need to
install the batfery under the fuel tank to
achieve proper balance. Use a scrap
balsa stick or rubber bands to keep
them from moving around during flight.
Summary of Contents for Four-Star 120
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