Hi Paul,

I have just finished re-reading your wonderful book on cooling the Wankel.
What a wealth of experience and information.

Last year I contacted you for your opinion about Mistral's rotary engine.  I
wanted to buy one.  Unfortunately at that time they decided to stop selling
to the experimental market until the engine was certified (policy may have
now changed).  Anyway, I decided to buy an LS1 conversion made by a company
called Geared Drives in Conroe, TX.  The man who designed and builds the
conversions is Bud Warren, a 40 year aircraft mechanic, pilot, and veteran
dragster mechanic and racer.  He knows a lot about engines.  If you have the
interest you can see his engines on the Geared Drives website.

Bud adapted his Corvette LS1 conversion to our Foxtrot Airplane.  I am
attaching some photos.  The Foxtrot is a 4 passenger high performance
airplane made by a company called Team Tango in Williston, Florida.  My son
and I are building it there at the company build center.  Theoretically it
will travel up to 230 knots, although I don't plan to fly that fast until it
is thoroughly tested.  The Williston Airport, where we are building the
airplane has extremely low traffic (20 planes a day, max) and an 8,000 foot
runway so it's going to be a good place for our testing.

The reason I am contacting you is for advice on cooling the radiators.  Bud
placed two radiators in the cowel, one on each side of the engine.  As you
can see from the photos, there is only about 2" space between the side of
the cowel and each radiator.  On the engine side there is much more space.
Per your book, it's better to bring air in away from the engine so it begins
its journey as cold as possible.  It looks like it may be a difficult design
problem to get enough air through the radiator from the outside (cowel side)
of the radiators.  I noted with interest your comments about NACA ducts
being inappropriate for this application.

The radiators were built to prevent hot water from building up in one part
of the radiator - but I don't exactly understand how that was done.  I think
each one is divided in half horizontally and the water has to travel through
most of the radiator.

The cooling fins on the pilot side radiator are 23-7/8" long, 14-3/8" high
and the overall depth is 2-1/8".  The co-pilot side is 23-7/8" long, 15-1/2"
high and 2-1/8" thick.  Any advise you might be able to offer would be
greatly appreciated.

There is quite a lot of space in front of the radiators and some below which
I think you can see in the photos.

Hope all is well with you.  I referred your book to a fellow builder who is
installing a Delta Hawk diesel on his airplane (if he can ever take delivery
of the engine).  He needs to build his cooling system from scratch.

Bob Mayer
San Francisco

I am not fan of automotive piston engines for aircraft use as the design
and materials used are not up to the continuous power required by an
aircraft engine. They could fail in a catastrophic fashion without warning.
There is a real reason why only the finest steels and manufacturing
processes
are used in real aircraft engines. For that reason I decline
to provide any help.

Read may article on the subject here.
http://www.rotaryeng.net/Rotor-v-Piston.html

Also obtain and read this book.

Sky Ranch Engineering Manual. This book presents an excellent
overview of the problems of aircraft engines. It is 500  pages and a
bargain at only $23. There are many details on the materials and
processes used to build a successful aircraft engine. There is a
very good and exhaustive discussion of destructive  torsional
vibrations and fatigue. The telephone number  to buy this book is
(916) 421 7672. The author is John Schwaner. John is highly thought
of in the experimental aircraft community.

Do not kill the messenger :)

Paul Lamar


It would seem that if Bud did the adaptation of the LS1 to your
airframe that he would be available to provide support to any cooling
issues you might have.  Otherwise, it sounds like you got some custom
parts from him, but are really on your own.

The LS engines are interesting.  They are a far more advanced design
than the previous generation of small block.  They have a lot more
meat in places where V engines seem to need it.  Some people claim to
be getting much improved performance from them as compared to
conventional aircraft engines in terms of fuel burn and performance.
The people with LS powered Seabees are among those that are apparently
succeeding.  I was around an RV-7A that seemed to work OK.  The fellow
that owned it was flying it from my home base in Nampa (S67) over to
Idaho Falls pretty regularly.  Others have not had achieved as much
success.  I don't know whether anyone has enough hours on one to
demonstrate reasonable reliability/durability.

I have the Sky Ranch manual.  I agree that it is excellent.


Matt-