James,

I have an engine test stand that was used to develop a NA 3B installation and is presently used in development of a turbo Renesis installation.  If a prop suitable for flight is used on the test stand, operation at high power causes the prop to cavitate.  When this happens, the sound is deafening and the vibration is also felt through the ground.  It is worth considering that extended operation of the cavitated prop may be detrimental to the longevity of the prop and possibly the operator.  I don't know exactly what "extended" means and it is something I hope not to find out.

FWIW

Steve Boese
RV6A, 1986 13B NA, RD1A, EC2  

________________________________________
From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of James R. Osborn <flyrotary@lancaironline.net>
Sent: Friday, October 30, 2015 9:12 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 20B with RD-1C Prop Options

Hi Bill,

Yeah after I sent that I realized slip was a much smaller difference.  The difference between top speed and standing still is 100% slip!

I don’t really know what to expect for HP.  I threw those numbers out there for feedback.  So what numbers say for unported site port, medium street port side port, and peripheral port on a 20B can we reasonably achieve?

Thanks for more input and numbers.  It will be interesting to try to work it out on the ground and the more I think about it, adjustability will be a real big help.  I did recall correctly that a friend has an old dyno I can borrow.  So I guess I will move in that direction first and set the prop selection aside for now.