Re: Sizing rubber and matching props

From: Bill Gowen <b.gowen_at_earthlink.net>
Date: Fri, 23 Mar 2007 13:03:29 -0400

Marty
When you have all the answers to your questions let me know how much you would charge to share the info!

For my next 2 competitions I decided to standardize the length variable. For each model I looked through my data to find the most common successful length and then made motors of that length with different cross sections. I've found that in most short contests there isn't enough time to explore a dozen different variables. I also don't have Jim Richmond's ability to calculate the exact motor I need and then put up one winning flight.

  ----- Original Message -----
  From: Marty Sasaki
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Friday, March 23, 2007 12:37 PM
  Subject: [Indoor_Construction] Sizing rubber and matching props


  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


   

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Received on Fri Mar 23 2007 - 10:03:52 CET