X-Mozilla-Keys:                                                                                 

Mike Cosman, designer of the Cosman speedster

responds;

Let's see now...

<nice math summary deleted>

I sure do like the way this guy calculates. PL

Me too.  Excellent envelope math.  Unfortunately I
calculated the flat plate drag using 207mph, the speed
that Mike Arnold said that he could attain in straight
and level.  

Now, Ron was burning about 4.1 gallons per hour

during the

Copperstate dash.  I would guess that the AR5 was

burning close to twice

that during its very short burst of speed, and

that the rotax was

probably
being pushed to provide much more than its rated

65 hp.  

This first point I conceed defeat.  The statement I
made was that Mike Arnold had a more efficient
airplane.  I should have stated that he had a more
efficient airframe.  The two strok is obviously going
to have a much worse BSFC than an air cooled flat 4. 
The second point I cannot contest.  I thought about it
yesterday a lot actually.  The one number most in
question, the horsepower output of the Rotax,was never
tested or questioned.  Seems to me all you have to do
is lean it out and change the exhaust slightly and you
may just be on the better side of 65hp.  But how far? 
I makes a big difference to the flate plate numbers!

Mike Arnold
could,
of course, should validate his record claim by

entering any equivalent

cross-country
air race and showing that he can go this fast

regularly, for meaningful

distances, under real-world conditions (Ron has

won Copperstate

twice...)

P.S. Look for Ron to better 200 mph next year

without overspeeding his

stock A65 engine.

The gauntlet has been thrown down.

Chris

But I don't think Mike will pick it up, now that he is
selling the plane.  I also doubt that the AR-5 is
comfortable for very long flights.  

Chris, could you provide me with some more of the
dimensions of the Cosmon Commuter? span, area, wetted
area, etc.  


Kevin Russert Walsh
Process & Equipment Development Engineer
Inhale Therapeutic Systems, Inc. (NASD:INHL)www.inhale.com

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