Fitting the Cowling
The cowl supplied with the kit is at best a crude product. Many hours of
work were needed to reshape and fit the cowling to the fuselage. The most
difficult part was reshaping the forward air inlets and spinner opening.
These areas did not line up needed much attention. After the two halves are
trimmed and the sides clecoed together, I was able to attack the inlets. Two
issues existed here. One is that the parts were twisted as they met a the
inboard air inlet holes. I required significant force to bend these parts
into alignment, then clecoing them to hold their position. not to worry
though...fiberglass is has thermoplastic qualities and these parts quickly
relaxed into the intended position as soon as LOTS of heat was added. After
the first couple engine runs, the parts were no longer fighting me, in fact,
they are now naturally aligned requiring no force to insert the screws.
The second issue is the
misalignment of the edges around the inlet holes. Correcting this required
lots of grinding and several treatments by adding a mixture of milled glass
fibers /epoxy. Lots of hours later, they look very nice. Time for diligence
here!
The upper cowl needs air inlet
ramps added to the upper inside surface. This smoothes the air entering the
cowl and improves engine cooling. I built up ramps with expanding A/B foam,
shaped it with a course cutter on a die grinder, and them fiber glassed it
to seal it from engine compartment vapors etc. Below you can see the ramps
prior to a layer of thin fiberglass. They work fine with engine temps well
under control.
The engine baffles need fitting at this point as well. The air inlet must
align with the engine baffles to allow smooth flow of air into the engine
compartment. In this picture, you can see I left a 1/4" gap between the aft
inlet edge and the forward baffle edge. Some builders will install elaborate
seals at this point. Initially I flew it without any seal here. Then I
sealed the small gap with some clear tape. It made no difference in engine
temperature and as such, I continue to fly with it just the way you see it
it with no problems. It's just my opinion, but I think the small amount of
air that leaks past this gap does wonders to cool the lower cowl and protect
the fiberglass from radiant heat damage caused by the exhaust pipes.
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Cowling
page 2
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Cowling page 2 