On Nov 22, 2:08*pm, "Marc J. Zeitlin"
wrote:

... for wood, it's the friction.
On the wooden props, the conterbores are there because the drive lugs
are there, but not to take the loads.
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The late John Thorpe said much the same with regard to using wooden
props on the GPU that powered one of his last designs (the 'Tiger'?)
Even more surprising was the torque specs for wooden props. As I
recall it was on the order of 14 lb-ft. Of course, the best joke is
the claims made by 'experts' selling prop hubs with drive lugs :-)
-R.S.Hoover