The Murphy Builders Site

The main reason for a high tip speed is for putting more power into a
prop when you can't increase the diameter due to ground clearance, float
clearance, picking up too much water spray, or torsional vibration
concerns with the engine. Full vibration surveys are expensive so just
spin the prop faster and the customer gets better performance but at the
expense of noise and fuel consumption. Customer doesn't care about
either if fuel is cheap and/or he only turns the high rpm at takeoff.

Reynolds numbers and such come into play but there is a reason that no
commercial jets fly at .9 M

Joe - haven't had a chance to look at that website yet.

Ken

Mike Kimball wrote:

I'm about ready to change the "good range" limits in my spreadsheet. But
I'm going to wait to hear back from the professor I emailed in the aviation
department at my old alma mater. Hopefully, the result of this discussion
will be that I don't have to change a thing on my plane! Disregarding all
the math and theory for a moment, it still just seems like my prop speeds
are just too low based on all the other planes I have ever flown since I
started flying in 1980. I know the M14 prop speeds are pretty low too, but
that means finding a giant prop to swap out for what I've currently got.

Mike
044SR

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