On Sat, 16 May 2009 10:58:14 -0400, "Peter Dohm"
wrote:



I have heard that the (so called) area rule has a considerable effect on
drag at surprisingly low speeds.

Presuming that is the case, the benefit of the smaller diameter engine might
be trivial, except on a single seater or a tandem two seater, so you might
also consider the Rotec radial.

Peter



rotec is not in consideration. my target is a light 40 hp engine for
single seat aircraft.