Sizing rubber and matching props

From: Marty Sasaki <marty_at_mss.tzo.com>
Date: Fri, 23 Mar 2007 12:37:36 -0400

This talk of prop efficiency and winding rubber, etc., has given me a
"Eureka!" moment. Of course this has been obvious to most. And I also
have a few questions.

It seems that the way to size rubber is to choose the size so that the
flat part of the torque/winds curve corresponds to the cruise portion
of the flight. Adjust the length for the number of turns remaining, if
you go deadstick, make the rubber longer, if you have lots of turns,
make the rubber shorter. Adjust the backoff to keep the model out of
the ceiling.

With VP props you change the top pitch to more slowly use the torque
peak.winds. I think I understand all of this, now for the questions.

How do you choose the prop pitch? You could use a low pitch prop with
thin rubber or a thicker rubber with a higher pitch.

You can also use different blade side and diameter. What are the
considertions for these parameters?

Thanks.

Marty Sasaki
Received on Fri Mar 23 2007 - 09:41:59 CET