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 Lips 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 [Lips] will design racing props, but Craig Catto actually makes most of
his props.  That phantom bi-plane really does smoke the field though!