Wrathall Mark wrote:

Frank Wrote> My guess is that props are made to turn at about 3000 RPM max
because 50

years ago that was about the max that a Lycont could turn.

If you check out WW1 airacrft powered by rotories, some of these had
performance approaching an RV-6, and ran huge propellors below 1500 rpm.
(Cleget 1200rpm, Le Rhone 1400rpm). GA aircraft turn 2500-2800rpm as the
best compromise between prop effiency and engine efficiency. If you are
going to a reduction drive you are freed from this compromise. Looking at
most prop driven aircraft with out this compromise, they mostly run a lower
prop RPM. If you are fitting a 13b to an existing design design, you still
have the prop diameter limitation.  Is it more efficient to run a two blader
at lycon design speed, or a three blader of the same diameter slower?

Mark Wrathall

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