Mike Wills wrote:

  Much has been said on the list about proper diffuser design on the intake
side of the rad/oil cooler. I was looking over some old email from Alan
Tolle and looking at a couple of pictures of Alan's RV3 in various magazine
articles. Both Alan's RV3 and Everett Hatch's RV4 used baffles to seal the
exit side of the rad and oil cooler to the cowl. This creates a large
plenum in effect making the entire engine compartment the diffuser. When
Alan flew his RV3 in the Sun 100 prelim a couple of years ago  my recall is
that it was the fastest RV there so apparently this config can be both
effective and pretty low drag. This type of config would ease my oil cooler
installation considerably. Do any of you guys have opinions on such a config?

  Everett's oil cooler was mounted high and behind the engine with the air
exiting at the top-rear of the cowl. Seems that this exit may be in or at
least near a potential high pressure area about 1 foot forward of the
canopy. Anyone have any comments on that?

  Ive been able to locate some pictures of Alan's RV3 but none of Everett's
RV4. The only pictures Ive seen are on the Powersport website. Does anyone
have any good pictures of Everett's RV4? Particularly interested in any
shot showing the oil cooler exit at the top-rear of the cowl and any
pictures of the airplane uncowled.

Thanks,

Mike Wills

I agree that spot is likely to be a high pressure area.
I would put a stock RX7 oil cooler on the right side of the cowl and let
the oil cooler air out the side with louvers or a cowl flap.
the inlet duct should have a curve in it with the skinny end towards 
the back to prevent unequal air flow distribution through the oil cooler core.

Dave Atkins uses louvers with this configuration on his RV6.
Seems to work as Dave has flown from Seattle to Florida several times
as well as OSH several times.

Tracy does something similar but it is not working too well as his
water rads block most of the incoming oil cooler air. We discussed mounting
the stock RX7 cooler near the top of the cowl about where it is now and bringing 
air in with a NACA duct on the top of the right side of the cowl.

Dave also takes air in for the horizontal rad located underneath the engine
with the regular inlets and lets it out the bottom in a conventional manner.
This looks like it should work with your configuration if you decide
to use a side exhaust. 

I have a lot of pictures of the Power Sport engine but none of the airplanes 
unfortunately. That was before I started this newsletter.

Allan had a lot of cooling problems on the ground as the water rad was
directly exposed to the radiant heat from the exhaust pipes.
I was there when he had to shut the engine down while waiting for
the start of the Sun 100. He nearly did not get it restarted with
the mechanical fuel injection then in use by Everett.

BTW Bill, Freeman  Tracy and I were sitting around the Rotary Engine campsite
discussing the advantage of electronic fuel injection. We decided
the main advantage of electronic over mechanical was the much better
hot start characteristics :-).

Paul Lamar
 
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