its propeller backplate at a distance of 5-15/16" from the front face
of the firewall. This distance is required to mount the cowl and still
have about 1/8" - 1/4" clearance between the back of the spinner
and the front of the cowl. Most gas engines in the size range used
on this airplane are shorter in overall length (including the muffler)
than this figure. Therefore, you will need to carefully measure the
length of your engine, from the face of its prop support, back to the
rearmost part. The overall engine length is subtracted from the
required 5-15/16" figure. The resulting number represents the
distance that the engine must be spaced and mounted from the
face of the firewall.
The simplest way to create a good spacer is to trace the outline of
the engine's mounting backplate (including the mounting bolt
locations) directly onto a piece of hardwood that is of the correct
thickness. Using a jigsaw, this outline is cut out. Next, the spacer
is drilled for clearance holes for the engine mounting bolts (for 8-
32 bolts this would be an 11/64" drill bit). Since this spacer will
cover the fuel tank neck at the firewall, a hole must be cut from the
center of the spacer, taking out as much material as possible to
clear the tank lines. The finished spacer is then epoxied to the
firewall in the centered position, using the horizontal and vertical
centerlines on the firewall for reference.
With the spacer now in place on the firewall, clearance holes for
the engine mounting bolts are drilled through the firewall. The
appropriate size blind mounting nuts are then installed into the
back face of the firewall - in the case of our F.P.E. 1.3 engine, we
used 8-32 hardware. These are installed using the same method
as described earlier in Step #4, in the 4-STROKE ENGINE
installation section.
❑
2) The fuel tank, assembled using gas-compatible Tygon
tubing for the fuel pick-up and a gas-compatible stopper, is now
installed into the fuselage. The installation of the tank is covered
in Step #14, in the 4-STROKE ENGINE section and is exactly the
same for the gas version.
❑
3) In order to route the two required fuel lines from the tank to
the engine and fuel filling valve, two appropriate sized holes must
be drilled through the sides of the wood engine spacer, at the
correct locations. The fuel lines are then fitted onto the tank fuel
tubes and routed out of the two holes. The "vent" or overflow line
will hang straight down. We made a simple sheet metal bracket to
anchor this line to the firewall, keeping it away from the muffler.
The fuel pick-up line goes directly to the fuel valve.
❑
4) If your engine has a Pitt's style muffler, it will probably
require exhaust extensions to clear the firewall at the bottom of the
fuselage. In the case of our F.P.E. 1.3, we used two 2-1/2" lengths
of K&S brass tubing, 17/32" in diameter (K&S #140). This tubing
had the perfect inside diameter to slip over the F.P.E. Pitts muffler.
We cut the exhaust end of each piece of tubing a slight angle to
vector the exhaust towards the rear of the fuselage. To hold these
two exhaust extensions in place, we used two small automotive
type metal hose clamps.
In order to allow the exhaust extensions to be clamped in place, it
is necessary to first "slice" them at one end, in four places. These
slices are made with a Dremel
®
Tool and a carbide cut-off wheel.
Make each slice about 3/8" deep.
Remove any burrs that may be in the way and slide the tubes -
sliced ends first - onto the muffler's exhaust tubes. Position the
tubes at the same length with each other and use the hose clamps
to secure them firmly in place.
❑
5) Our F.P.E. engine operates with an electronic ignition. This
feature eliminates a great deal of bulk (weight) from its
construction and makes for a much easier starting and smoother
running engine. The ignition module is a small separate unit that
must be installed in the nose of the fuselage, behind the firewall.
It must be close enough to the engine to allow the wiring to reach.
The module wiring consists of the spark plug lead, the ground
wire, the electronic ignition module connection to the prop hub
sensor, and the battery pack lead. The battery pack lead stays in
18