That's interesting news, Will.
Assuming the desire is to find the size/pitch that says quiet at 13-1/2" of diameter ...
If we assume a 5.0 seconds lap on 70' foot lines and the "rule of 130" that says that prop tip noise will not be an issue if RPM X diameter is less than 130,000 inch-RPM, then ...
The theoretical pictch of the prop will be 6-1/2 inches.
Given that we typically measure the pitch at the flat face, this means a 5-1/2" pitch.
So I'd suggest a 13-1/2 X 5-1/2.
Bass or Beech with carbon veil stiffening might be a killer lightweight setup.
Dean P.
Hi Dean; What I meant by the comment is, that I find the APC lower pitched electric pusher props noisier than
the higher pitched props I use. I don't like noise in electric format. electric needs to be kept quiet -
that is just how I feel, and no consequence to anyone else. I do not understand completely the technical principles you mention
here - but I can still observe. My system I am using, which incorporates an Orbit 20-18, with a
RPM/volt rating of 640, seems to like the rpm range the APC thin electric 13/6.5 pusher prop delivers on 5 cells, on 64 foot eye to eye
lines and a lap speed of 5.2 to 5.3 I can judge, with some accuracy, to what I see, what I feel, and what I hear.
And what I have right now works for me and keeps me and the airplane happy.
I don't think I will be suggesting anything to the Yatsenko brothers anytime soon with regard to prop design. They seem to know more about
props than I do breathing. I want to stay on very good terms with these fine men, but there is a bit of a language
barrier . so I would have to be delicate and very clear with my suggestions so as not to make it all go sour. They seem to have very specific ideas about props, if you read their website on the subject.
But I agree, a stiff prop may be excellent. Their Sharks are excellent with wood.
And I agree, a 13" to 13.5" 5.5 pitch prop may still work with my system. Are you finding
lower pitch props working better in the maneuvers, in electric ?
Please keep the ideas flowing, and thank you Dean for your suggestions.