On Dec 20, 6:49 am, GTH wrote:
a écrit :

Opposed engines have less drag than a radial

Agreed

or vee

Why would it be so ?
An opposed engine is much larger just behind the prop, when a Vee is
more easily streamlined.
Would you care to elaborate ?

Best regards,
--
Gilleshttp://contrails.free.fr

A vee takes up as much flat-plate area as an opposed, because
it's not likely to be cowled so the slipstream can flow through the
vee between the cylinder banks. The opposed and vee both have
crankcases and cylinder banks that are in the way, and the case of the
vee tends to be larger, forming a three-armed affair rather than the
two of the opposed. Some opposed engines have been very tightly cowled
for racing purposes, with the carb and such behind the engine instead
of under it.
Most vee-engines have some sort of reduction so that higher
hp can be obtained from a smaller configuration. These can be smaller
than opposed engines for the same hp, but they'll be heavier, too. A
direct-drive vee is pretty big. The Argus was one.
The inline engine is much more easily streamlined, but its
crank is longer and so has to be larger in diameter to obtain the
stiffness required, and as it gets larger it gets heavier.

Dan