Mike Wills wrote:

 Jerry,

    I very briefly considered doing what you are talking about with my RV
 but since the RV skin is structural cutting into it for scoops and ducts
 was an issue I didnt want to deal with. Obviously not the case for
a Tailwind.

   However there is additional weight involved in what you propose. Not only
 the extra radiator size and the extra coolant in that rad but also the
 weight of the coolant lines and the coolant in those lines.

   Then there is the issue of ground cooling. With your inlets located well
 back from the prop blast cooling on the ground could be a
significant problem.

   In my opinion the best option is to keep the cooling system components
 under the cowl if at all possible. Seems that should be doable in just
 about any side-by-side aircraft like a Tailwind. A little harder in narrow
 aircraft like the RV3 or RV4 but even that has proven to be workable.

 > Mike Wills

 Mike,  Thanks for your response.  I am a beginner when it comes to
engineering a radiator into a tight cowl.  The radiator I am
proposing is about 900 cu in (it got smaller) and includes the oil
cooler.  If it works, then there would probably be a slight weight
savings over seperate radiators and oil cooler. (500 to 600 cu in
for typical radiator and 300 cu in for Mazda oil cooler)  The major
issue for me is finding the right place for the air inlets.  I
studyied the air flow map for high wing aircraft just posted but
hardly achieved clarity.  Like Paul said, it looks like there is no
high pressure anywhere.  The Griffin radiator/oil cooler combo is a
special order item and will cost about $650.00 or more.  I won't be
sending them a check until I am convinced I know what I am doing..
A friend has a Tailwind.  I am going to make my own air flow map
using some yarn taped to the fuselage. I will soon know the reality
of this issue.----Jerry

I am not sure I would take that pressure map  as typical of a Tailwind Jerry.
In fact I am not sure it is accurate for even that airplane.
All airplanes have high pressure someplace as that is how drag
is generated. 

I strongly agree with Mike on this. You would be better
off with separate radiators. The heat transfer from oil to water
in that radiator is designed for a piston engine that has a different 
heat balance than a rotary. In other words less of the cooling is 
done by the oil in a piston engine.

Paul Lamar
 
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