Re: Re: Prop design

From: Fred or Judy Rash <frash_at_chartertn.net>
Date: Wed, 24 Jan 2007 23:03:09 -0500

The spreadsheet should still be in the Yahoo Indoor_Construction files.

Fred Rash

  ----- Original Message -----
  From: doctorgonzo788
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Wednesday, January 24, 2007 8:11 PM
  Subject: [Indoor_Construction] Re: Prop design


  --- In Indoor_Construction_at_yahoogroups.com, "barrysholder" <barry@...>
  wrote:
>
> Please excuse my lack of terminology but, If I have a sheet prop blade
> cutout and I form it on a 4" dia form and the same on a 6,7, or 8" form
> (same angle) given the same pitch,what difference in performance might
> I see. I'm trying to come up with some Nocal props and these questions
> keep popping into my head. Thanks
>

  The short answer is "not a clue"

  Now for the long one...

  Forming blades on a cylinder at an angle is an easy way to approximate
  helical pitch distribution, and adds camber to the blade as well. I
  know Fred Rash has done some work on a spreadsheet for cone-shaped
  forms, which do even better with the distribution. I would guess that
  using a larger diameter form would be detrimental, because the blade
  will have a)less camber and more importantly b) severely washed in
  tips. Tip-stalls and their related drag are a big efficiency killer.

  I say, do a little leg-work and figure out what diameter form and what
  angle will give a pitch distribution that is closest to helical.

  Or, make a bunch of props. Could be more fun.

  Fred, is your excel spreadsheet available online anywhere?

  Chris
  Building cat II DLG's in Atlanta



   

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Received on Wed Jan 24 2007 - 20:07:22 CET