prop formula

[Bob Pastorello]

The weights on that website are horrendously inaccurate.  The sizes mentioned go from about 3.7 - 4.6, with the 18 x 8W being the heaviest, it's 5.2.

Bob Pastorello
rcaerobob at cox.net
www.rcaerobats.net


  ----- Original Message ----- 
  From: Jeff H. Snider 
  To: discussion at nsrca.org 
  Sent: Thursday, October 21, 2004 5:18 PM
  Subject: Re: prop formula 


  Thanks for the feedback.  Nothing that can be done with paper
  and pencil, or keyboard and cpu, replaces going into the field
  and making some real world observations.  But having an
  analytical brain and being a former student of Math and Physics
  I really like being able to calculate my way through a problem.
  Plus having a theory to support what I see happening in the
  air does a world of good for my rate of improvement as a pilot.

  I missed reading about Jim Woodward and his 18x10 prop.
  Where was that?

  About multi-blade props.  APC's website says they roughly weigh:
   17" 2 blade .07 lb
   16" 3 blade .10 lb
   15" 4 blade .46 lb!
  Is that a typo?  Does a 4-blade add over 6 ounces to your
  nose?  I'm ready to give this multi-blade bandwagon a test
  ride, but no one is flying a half-pound prop!  Are they?

  As Dean says, this is fun stuff!  I need to read up on
  that guy Renard.  Anyone have a suggestion for a good book
  on the subject?  I have "Model Aircraft Aerodynamics" or
  something similarly titled, which gave me my first exposure
  to the amount of art pervading the science of aerodynamics.
  (By my calculations, at the present rate of improvement
  in technology we're 120 years away from being able to use
  our desktop computers for a full and complete molecule by
  molecule realtime simulation of air flowing over a wing.
  Maybe by then science will have more fully displaced art.)

  -Jeff
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