The big reason for the "drive lugs" is to remove the nuts from the airstream
in back of the prop and reduce the drag the produce. If they are the only
drive mechanism, the recessed holes will quickly be beat out. If they did
do the job, you could have one center bolt. Many props such as used on A-65
don't even have drive lugs but use bolts straight thru.


--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A 46 Year Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot


"Morgans" wrote in message
...

So you are correct that friction is used in tranferring torque
in
wooden props. They also use counterbored drive bushings to transfer
the torque. I'd be willing to bet that the bushings transfer most of
it, but that is only a guess.

Thanks.
--
Jim in NC

I spent some time talking today at lunch with some friends who are
structural engineers, about this issue of friction delivering torque
to the prop. They said that if the strength of the attachment of the
prop to the flange had been determined through experience, then
eliminating the friction load path for the engine torque to be
tranmitted to the prop could result in failure of the junction of the
flange and prop, but that it wasn't likely.

I'll bet that you structural engineer friends are not experienced with
wood props, and their failure modes. It seems to be their own unique
circumstance. It has been found that the props fail, not the bolts.
--
Jim in NC