X-Mozilla-Keys:                                                                                 
Vance and Emily Jaqua wrote:

On Thu, 01 Jul 1999 12:49:20   Paul wrote:

Vance and Emily Jaqua wrote:

Paul - If you get a chance send me a few estimate
points for horsepower versus Rpm for Perry's engine
in it's present configuration. I have a family of
 prop programs that I have been working on for
years, which should let me do a decent cut on
fan blade width and pitch, and then a rough
prediction of engine rpm and thrust at various
plane speeds. I will then do a similar estimate
for a typical piston engine prop combo that would
be suitable for an Ezee - These are all for naked
props - but I think in our speed range the best
thing a duct can do is not degrade the prop
performance -  Vance

The solid curve is the curve for the 160 HP normally
aspirated engine.
Perhaps Perry has the 180 HP normally aspirated engine.
I am not sure.

Paul Lamar

Thanks Paul and Perry - I have printed both curves
out and will get back to you with an estimate. The
raw program results for a 67 in dia 74 in pitch
prop on an EZ class airplane show satic rpm at
roughly 2000 which is about 320 lbs thrust. I
suspect that this is a bit pessimistic, since I
 doubt that they would settle for 2000 static.
Also wood props flex - and the good ones are
probably doing a little of that" almost const
speed" thing. Centrifugal untwist increases pitch
and thrust bending flattens pitch if you do it
right. The shorter lighter fan blades will probably
do this much less - and Perry's blades look quite
stiff (also over wrapped with composite)- Vance

 
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