Sorry it took so long to get back but I'm in Hawaii right now so
access to the internet is limited (laptop+digital cell phone).

The vast majority of GA engines don't use radiators so none of the
large manufacturers are interested in pursuing a project with only a
niche market (and budget concious one at that), so this may be another
reason.

And you bring up a good point, who can build one and the rest of an
entire airplane. Most people are so busy doing all the other things
the have to do (work) to be able to spend time/money doing experiments
but thats part of the reason for bring it up here- so we can get lots
of eyes and brains on the problem. Some people that have done work in
this area can bring up points, and maybe somebody will say "I work in
a brazing shop, we make something like that for XYZ application."
I've seen some stuff real close done by the guys that do forced air
cooled cabnets for avionics. No doubt, construction will have to be
done by a specialist or someone that will become a specialist. I'm
writing in this newgroup more for the expermintal part and less for
the home made part.

Mechanical stresses- I can definitly see this would be a problem if
the radiator is a structural element or ridgedly attached to one at
multiple points, but what I'd imagined was some part (or whole) of the
lower cowl. That cowl region being critical because it has access to
that nice cooling turbulent air right behind the propeller. 3 blades
might do better than 2 for this style cooling. The only weight it has
to support is itself. These things are often times fiberglass so they
aren't all that strong.

From what I've read of the radiator imperical studies from the "golden
age", producing a turbulent flow was key cooling efficiency per unit
area.

For a low speed aircraft (100MPH) an auto radiator makes more sense
than something custom like we're talking about here.


Regards