Ken responded:

Yes, I understand that.  I was just stating that there is not a lot of
difference in prop efficiency  between prop diamenters of 64" and 76",

so it

doesn't matter a whole lot if you run a 2.17 or a 2.85 redrive.  The

important

variable here is the airfoil section of the prop needs to be efficient

up to

about .85 mach.  IIRC, Bill F. stated that a  Clark-Y is awful above

about .75,

as are the 2000 series.  BTW, I do not think that you can turn a prop

with a

Clark-Y or 2000 series airfoil 900 FPS at 12000" without running into

the drag

problems assosiated with tip speeds approaching mach.  Does anyone know

what the

speed of sound is at 12000 ft and say 30 degrees F.

Ken Powell

Yvon Cournoyer wrote:

Is this any help?
Yvon

 
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