We have an engine that will make 250
  HP.
  Target speed for an RV4 is 225 MPH.
  We intend to race this airplane.

  We think a 4 blade Warp Drive will absorb the HP.
  What is the maximum twist angle change you can
obtain
  by tapering the blades. I know the twist is less
then
  theoretically ideal. We are willing to accept that
  as the features of ground adjustable and carbon
  construction
  make the Warp Drive unique and better in the field
of
  props.
  IMHO that outweighs the less than ideal theoretical
twist
  distribution.

  I know you lose blade area as the twist is increased
and
  the tip cord is reduced. What taper do you
recommend?

  I would like to see a twist angle plot verses the
blade
  radius for the taper you recommend.

  This I think is ideal theoretical twist distribution
for
  231 MPH.
  Radius in feet.
 
----------------------------------------------------
  MPH = 231.8
 Radius...Circ MPH....Cord MPH...0 Angle of Attack
 0.3.........48.2........236.8......78.26
 0.5.........96.4........251.1......67.42
 0.8........144.6........273.2......58.05
 1.0........192.8........301.5......50.25
 1.3........241.0........334.4......43.89
 1.5........289.2........370.6......38.72
 1.8........337.4........409.3......34.50
 2.0........385.6........449.9......31.02
 2.3........433.8........491.8......28.12
 2.5........481.9........534.8......25.69
 2.8........530.1........578.6......23.62
 3.0........578.3........623.1......21.84

  Twist = 56.41    Ratio Twist/Root =
0.72    Ratio Twist/Tip = 2.58


--------------------------------------------------------------------

  Paul Lamar

 This sounds like an ideal application for a Paul Lipps
type
 propeller.
 The Phantom biplane has won a Reno with his 3 and later 4
 blade props.

 http://www.eaa.org/experimenter/articles/2009-02_elippse.asp

 Erik


 Is Paul Lips selling blades?

 Paul Lamar

Paul Lipps designs and Craig Catto builds them.
Erik

Anybody have an email address for Paul Lips?

Paul Lamar



I don't have an e-mail, but he posts on the RV forums and has written articles for Contact! Magazine. Maybe you can track him down there.
I think you have a good candidate for his prop.
C. Smith