Al Gietzen wrote:

in Atkins' mount plate (made for a 13B), and in the Ross drive; not in

the

engine flange (20B).  And having the exhaust go through the prop out

where

most of the thrust is being produced may give a performance penalty.

Al

What is your reasoning on that Al? The prop is in the wake of the
wing anyway.

Well; the prop's job is to accelerate air.  In the wake, the air has been
slowed down, and although a bit more turbulent, the prop can generate good
thrust by speeding it up again.  Whereas; the exhaust is hot, low density
gases moving rapidly through the prop resulting in not much or zero thrust.

This touches on a whole 'nuther issue with pusher configuration that
requires a different look at "drag" like cooling drag.  In a tractor config,
discharging air slower than the plane's speed causes drag.  In a pusher, it
gives the prop a chance at a greater momentum change of the slowed down air
for greater thrust.  At least partially offsetting . . . .  blah, blah,....
we don't want to go there.   Besides, there's always the chance that I'm all
wrong.

Al

 
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