Paul,
That thicker radiators seem to have disappointing performance appears to me to
have more to do with the plenum than radiator - like the P-51 had quite thick
radiators, but also a very good plenum.  As Ed pointed out a couple of days ago,
the pressure drop across a thick radiator is not nearly as much higher than the
drop across a thin radiator as one would expect.  On a pusher, you have a better
opportunity to create a really good plenum than would be the case (under cowl)
in a tractor configuration and one might find that for a given volume, thicker
radiators might be a better use of space than thinner units with more frontal
area.  That  being the case, a couple of 535 ci radiators should be more than
adequate for even a turbo'd 13B even on a hot day climb.  It would appear that
you could even afford a somewhat compromised plenum.  Given the much more modest
cooling requirements in cruise, the excess air can be dumped/bypassed ala' John
Slade's plenum flapper valve scheme.  Bypassing radiators should be easier to do
with better recovery of cooling drag losses in a pusher than in a tractor.

When I get to that phase, my plan is to use the Cozy NACA duct (perhaps
supplemented with a lip that sags into the airstream) for radiators and oil
cooler with additional NACA ducts in the turtleback for the intercooler.  I aim
to employ a bypass scheme like John's to greatly reduce the drag penalty of all
the "excess" cooling needed for takeoff and climb.

Bottom line:  Plenum Rules!! ... Jim S.

>   Hi, Ed.....While looking at the various evaparator cores in the catalog at
> AutoZone, I came upon two cores that are 7 inches thick. The one I am
> interested in is 8 3/4 x 8 3/4 x 7 inches thick. If I were to use two of
> these side-by side, I would have a cooling area of around 1071 sq.
> inches.(minus end tanks, etc)  Getting the air to flow through a 7" thick
> core might just work in my canard at 200 mph,  but of course I'm concerned
> about take-off and climb. I can live with higher speed/lower vertical climb
> operations, I am most interested in perfecting cruise operations, (which
> should constitute about 95% of my flying) For ground operations I might be
> able to find a small enough diameter fan.  If I could make this work, it
> would be a neat, compact installation that would fit rather nicely in my
> SQ2000 without having to modify the cowling, etc.  What are your thoughts on
> an evaparator core that is 7" thick?  Thanks in advance for your thoughts
> and opinions.  Paul Conner