Engine And Fuel Tank Installation - SIG RASCAL FORTY Assembly Manual

assembled. We suggest using a simple two-line fuel system in this
airplane. One fuel line is connected to the fuel pick-up or "clunk"
line and the engine's carburetor. This same line is then used to fill
the tank (if you are not using a fueling valve system). The second
fuel line is the overflow line for use when filling the tank. After filling
the tank this same fuel line is then connected to the engine's
muffler pressure nipple to provide manifold pressure to the tank.
Note that the rubber stopper for the tank has two holes all the way
through it. Use these two holes for the two aluminum fuel lines.
Gently bend the aluminum overflow tube upward to just reach (but
not touch) the top of the tank. Adjust the length of the internal
silicon fuel tubing to allow free movement of the fuel pick-up weight
inside the tank. Insert the stopper assembly into the neck of the
tank and secure it by tightening the compression bolt in the center
of the stopper assembly. Slip short lengths of silicon fuel tubing
over the aluminum fuel lines and identify each as "vent" and "carb"
with small pieces of tape. This helps later when connecting the
fuel lines to their proper locations. It is more convenient to install
the fuel tank after engine installation.
OPTIONAL:
Because of the inverted position of the engine in this design, we
wanted to make the fueling and de-fueling process as simple as
possible. To do this we installed a Du-Bro #334 Kwik-Fill Fueling
Valve onto the firewall in the engine compartment.
To mount the fueling valve, we made a simple 90
a 3/4" wide strip of K & S .060 aluminum sheet. This bracket, with
the valve in place, was then attached to the firewall using a couple
of #2 x 3/8" socket head sheet metal screws.
If you choose to mount the valve in the side position, as we did for
our 2-stroke engine, then a smooth, round hole must be made in
the side of the fuselage. This hole must be directly over the center
of the fuel valve to allow the fuel probe to be inserted into the valve
for filling and emptying the tank. Note that this valve can also be
mounted with its face pointing straight down, as we did in the
4-Stroke Engine Installation. Mounted in this position, the need for
a hole in the side of the fuselage is eliminated. The nice thing
about this fueling system is its convenience, simplicity, and the fact
that it only requires the two basic fuel lines to function. If you wish,
a third fuel line can be used for fueling and de-fueling purposes.
This dedicated third fuel fill line requires a second "clunk" fuel
pick-up line inside the tank. The new Du-Bro #840 "Fill-It" product
would be a good choice for this type of fuel tank set-up.

ENGINE AND FUEL TANK INSTALLATION:

This phase of assembly requires some custom installation work,
based on the particular engine you've chosen for your Rascal
Forty, (note that both right and down thrust adjustments are
pre-built into this airplane).
instructions have been separated into two general engine types -
typical .40 - .46 2-strokes and typical .40 - .52 4-strokes.
The basic design of the RASCAL FORTY calls for mounting the
engine inverted in the nose. Over the years there have been
stories about inverted engines and how they run, primarily having
to do with "flooding". In our considerable experience with this
airplane and with running engines mounted in the inverted
position, we've found that both two and four-stroke engines work
perfectly fine in the inverted position, with no more tendency to
"flood" than engines mounted in other positions. Many, many
model aircraft designs use engines mounted in the inverted
position. The difference can generally be found in the starting
procedures used by individual modelers.
Flooding is caused by an unwanted siphon effect from the fuel tank
to the engine's carburetor. Note that the position of the fuel tank in
this design has taken this into consideration. However, siphoning
can be minimized by remembering to keep the carburetor closed
between flights. If you are using the Du-Bro #334 Fueling Valve,
siphoning can be totally eliminated by inserting the filler probe into
the valve between flights. Doing this closes the fuel line to the
carburetor completely. When first starting the engine, keep the
6
O "L" bracket from
The following engine installation