Hi Dave,
I am surprised Chris actually increased the gill openings. We found
them very harmful to engine cooling (in flight) and closed them off
(three of the four). The air from the two round inlets (on each side of
the prop) would flow across the top of the engine and out the gills,
without cooling anything significant. After closing them off, we saw
the cooling air from the round inlets go down the back of the engine and
out the bottom of the cowl, also without providing much cooling of
anything useful. After closing off the area behind the engine (between
the foot wells), we finally got sufficient cooling air past the
cylinders and exhaust, lowering oil temps 20 degF and peak in-cowl temps
200 degF.
Remember, the Rotax has liquid cooled heads and air cooled cylinders. It
is the air from the small round inlets that is supposed to cool the
cylinders (and exhaust system), not pass directly out of the cowl
through the gills.
Even after closing off the gills and between the foot wells, the
temperatures at the top of the cowl (carbs, ignition, etc) remained
within a few degrees of ambient.
Regards,
Terry Seaver
A135
---> I would think you would want a cooling setup similar to any other
air-cooled
aircraft, then. The engine should have a sort of plenum setup and baffling
like you'd see on a Lyc. or Continental. This would block off the rear portion
of the cowling from the incoming air with baffle seals to the top cowling,
forcing the incoming air to flow down past the cylinders, out the bottom of the
engine, and out the lower portion of the cowl. If there are areas of the rear
of the engine and/or firewall that need cooling, you can then tap off from
the rear engine baffle with SCAT duct and blast tubes to keep stuff cool.
That's how our little 140 is setup and it works just fine, like all the other
air
cooled bug smashers flying. Of course, the cowl openings are large enough
to drive a Buick through and I'm sure there is a very large amount of cooling
drag (as well as every other type of drag).
I've not studied the Europa XS cowling setup that much, and we're not to that
point
yet, but it indeed seems like a valuable place to spend time, as I've read
alot about cooling problems and such with the Europa on the ground, and even
marginal cooling in the air.
Chris
A159
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