<<However those of you who are interested might want to
look at an article in the August 2003 "Sport Aviation" on air cooling.  It
had an Excel spreadsheet which enables you to calculate the optimum
dimensions etc, and calculates the resulting drag.  The spreadsheet is still
available on the EAA website and can be downloaded.>>

Does anyone have the complete article that they could scan or FAX to me?
That's seems to be the one issue I haven't saved and the one I need right
now.

I have also been following the plenum debate and feel the need to add my
opinion.  Certainly a plenum that closely follows the contour of the cowl
does nothing one way or the other for cooling drag.  Eliminating the leakage
is a good thing, but a carefully fitted rubber flap against the cowl will do
that.  The most important thing, I think is the diffuser configuration
between the inlets and the large volume above the cylinders.  A problem with
a plenum is that the space above the front cylinders is very limited and it
is difficult to get good airflow above those cylinders without over-cooling
at least a portion of those cylinder heads and pre-heating the air to the
rear-most cylinders.  The best approach would be to have a constant velocity
of air into the plenum and down through the cylinders, but that is pretty
much impossible as there are too many things in the way.  So the best
compromise seems to be a relatively stagnate air volume above the cylinders,
as little leakage as practical, and a good diffuser ahead of the engine.
The diffuser part is what's ignored by Lancair, but not by Mooney - check
out an Ovation.

Gary Casey