I seem to remember that Tracy is turning up to 6500 engine RPM
which is 2995 prop RPM.  If he is running a 68" dia prop (normal
for a RV-4), he is

probably hitting

the upper tip speed limits for a clark-y airfoil.  This problem
is worse

at altitude since

the speed of sound decreases with altitude.  This is verified by
both the

John Ronc

and Joe Dubner prop sim programs.  I'm waiting on Tracy's 2.85
redrive

just for this

reason;  2596 prop rpm equals 7400 engine rpm - gotta have the HP
like a true gearhead!  In a previous conversation with Tracy, he
favors the 2.17

redrive and the

high prop rpm that goes with it.

Ken Powell

Ken,

Can you send me copies of these prop programs?  I'd love to compare
thier software to mine.

Thanks.

Bill Freeman

Here are some versions from about a year ago.
Ken may have some later versions. If so send it to me as well
Ken and I will add it to the collection.

I have some other prop programs as well. Some require
QB running under DOS in a Windows window if you can handle that.

Paul Lamar

Paul and Bill,
You can find the latest version of the prop program by Ed Dokus and Joe Dubner at:
http://www.nicon.org/chapter328/PropDesign/

I have also attached the version I am using plus a couple of speadsheets by John
Ronz.  This is pretty enlighting stuff for the amateur.

Ken Powell

Here are the John Ronz spred sheets.

Paul Lamar
 
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