Speaking of  a rad under the engine Tracy mentioned at Shady Bend
that the air temp inside his cowl was 50 degrees F higher than
outside air temp. I was a bit skeptical about this as I knew
the rad only heated the air 10 degrees F or so. The rest of
the heat must be coming from the engine block and the exhaust.

I just realized part of the reason we have had so much
trouble cooling the rotary is most people have the rad
in the cowl dumping hot air into the cowl. Duh! The heat transfer
rate between rad and air is a strong function of the difference
in temp. If the rad is 220 and the air going through it is
100 the difference ie 120. All well and good.
However if the rad is immersed in air that is 150 F the
difference is only 70F!!!!!!

Ding Dong!!!

In other words the back half of the rad is not working
anywhere near as well as it would work if isolated from
the cowl with ducting fed cold air and dumping hot air directly
over board. Duh! I wonder why I did not think of this four
years ago? Furthermore there is the flow blockage effect
of the rad being too close to the engine and other objects
under the cowl.

We have lots of evidence for this effect in the various
configurations out there such as; Perry Mick, Ted Nichol
and Mike Hersfield all using external rad air exits, ducted
inlets and much  smaller rads.  We have been blinded by
automotive practice dumping hot air into the hot cowl volume.

Paul Lamar

  This was another consideration in my decision a couple of years ago to
setup my rad ducting for top to bottom airflow. Its not clear to me just
how significant this may be but it seems logical. Now if I can just get
this thing flying and prove that it works.

  I've also redone my oil cooler install (again) and am doing the same
thing with the ducting there. Oil cooler mounted near the top of the cowl.
Inlet feeding a duct into the bottom/front of the cooler. Exit air in a
sealed duct out the top of the cowl with venetian blind style cowl flap on
the outlet. The cowl doesnt look as good as it used to, but I finally have
an oil cooler installation that I have some confidence in.

Mike Wills

 
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