Tracy Crook wrote:

Here's some progress shots of Bernie Kerr's RV-9A project.

Amazing

how

that

Griffin rad fits in the cowl .

Tracy Crook
tcrook@rotaryaviation.com

Yes it fits but the back side is not unobstructed enough
and the exhaust will transfer a whole lot of heat to the
back side of the rad. Good luck Burnie :-)

What does he have against putting it under the engine?

Paul Lamar

Hey Tracy!
Bernie's rad looks great!  Shouldn't be any problem with heat if

he uses

a

heat shield on the exhaust.
Vaughn.
PS, who's redrive is that?

It still won't work. The necessary heat shield will add further

obstructions

behind the rad. In effect it is little different than the Power

Sport

rad mounted too close to the firewall. That also does not work. Am I

really

saying this or is it my imagination. Is anybody reading this?
What have I been doing the last four years?

Paul Lamar

Hello Everyone,
     For those of you who do not know Bernie Kerr, he is a retired
engineer from Pratt & Whitney - used to design jet engines for a living.
He knows a thing or two about airflow.  I would suggest that he is well
aware of the limitations that have been discussed.  Exhaust system and
radiator installation is a compromise (as those of us who have actively
worked on it know).  I would bet that Bernie has sized his radiator to
work despite the negatives discussed here.  I would bet that part of his
objectives is to NOT build a new cowl (or extensive fiberglas work, he
is a RV builder afterall!) and to have a simpler exhaust system.  This
is really sorta fun; Paul or Bernie one will have to 'eat crow'
eventually.  Bernie will be flying within the year so we should know by
Tracy's flyin next year.  I think that we will eventually see that every
aircraft has a potential 'perfect' installation but when trying to
install around existing cowls, landing gear, etc. many compromises will
be made.  The further you stray from the ideal the less efficient the
installation, maybe to the point where things will not cool well enough
to be functional.  Note that an inefficient installation will also cause
a higher fuel burn and slower speeds.
     Paul, there are many of us who do follow your advise.  I have
designed my entire installation around the 'under engine' radiator.
Unfortunately, I am years away from flying so I will not be the one who
proves you right (or wrong).

Ken Powell

Hey Ken it is not me!!! I am not to be proved right or wrong. I am just 
the messenger! Read the references I have provided such as Kuchemann & Weber,
Kays and London and Sig Hoerner. Travel around the country to most air shows
and take pictures of radiators installed in airplanes and talk to the
pilots.  By all means repeat my full scale experiments and design and build
experiments of your own and find out for yourself. 

I have had extensive discussions with Burnie (:-)) and I will tell you
there are large gaps in his knowledge about these particular
installations. A turbo jet is one thing. A radiator installation
is an entirely different thing. There is no analog to a radiator 
in a turbojet. I have no idea what part of a turbojet that Bernie
designed but I will tell you one thing. Pratt and Whitney is
not a lot different than General Motors or Boeing. No one engineer
gets to design the whole product.

However that is not to say Bernie is not secure
in his knowledge. He does not need to be on the Internet. He reminds 
me of Tracy a little bit. I think it could be a regional trait :-)

Paul Lamar
 
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