I'm just about ready for the baffle fabric seal on the top but I want to
add a couple of things first. I need two scat ducting connections to
feed fresh air to the cabin heat muff and to the carburetor heat muff. I
also need a safe way to pass the upper spark plug wires through the baffles
on each side of the engine. Here is the 2" flange for the scat ducting,
and the spark plug wire pass-through (Aircraft Spruce P/N 375), installed
on the rear left side baffle:
A scat ducting hose will attach to the flange shown in the above picture
and will be used to feed the air to the heat muff for the cabin heat. A
good trick that will pre-heat the air even before it gets to the heat muff,
is to install this flange low enough to be right next to the fins of the
cylinder head. If you look closely you can see the fins through the
hole.
The 2" scat ducting flange for the carburetor heat system is mounted on the
right side rear baffle as shown here. The flanges are just drilled and pop
riveted to the baffles.:
Along the bottom of the baffles, there are wide tabs that sort of wrap around
the bottom of each cylinder. These tabs make the cooling air stay in
contact with the cylinder fins as long as possible, so it can pick up the
heat and take it away from the cylinders. Each tab has a couple of
small holes in it. Safety wire is used to pull the tabs up tight to
the cylinders. Starting with the front tab, I put the safety wire and a washer
to act as a doubler, on the tab as shown here:
The safety wire is then twisted with some safety wire twisting pliers
(or by hand if you wish) and a protective piece of nylon tubing is slipped
over to protect the wire and the cylinder fins.
Next the safety wire is fed through under the cylinders and the ends are
slid into the holes on the opposite tab (on the rear cylinder). Another washer
is slipped on, and then pulling the two ends tight, the wire is twisted to
hold the two tabs against the cylinders:
Note that the oil drain tube for the rear cylinder was temporarily removed
to make things easier.
I used some Red High-Temp RTV to create a seal between the baffles and the
engine case anywhere there was a gap:
The final part to install on the baffles is the fabric baffle seal that runs along the top of the baffles, to make an air-tight seal between the baffles and the cowl.
I started by drilling some 1/8" holes, spaced 3" apart and 1/4" from the edge, all along the top of the baffles.
The baffle fabric was cut into 3" wide strips and installed with 2" sticking
up above the baffles:
Note that the strips are split and over lapped where the baffles will
come apart is disassembled. The cut fabric looks a bit ragged because the
scissors I used were dull.
Vans supplies the large headed rivets to attach the fabric to the baffles.
However, the supplied rivets are too short to go through the doubled
aluminum where the side baffles are reinforced. In those areas, I used
a longer regular pop rivet with a washer:
The top rivet is the Van's supplied rivet, the bottom is the longer regular
rivet and washer.
Click here to go to Engine Baffles page 8