Low Speed Surfacing Propeller

Discussion in 'Surface Drives' started by dgruenwald, Dec 3, 2005.

  1. sandhammaren05
    Joined: May 2009
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    sandhammaren05 Senior Member

    Having raced both V-bottoms and tunnels, and doing my own prop work, I can tell you that you cannot replace cup by larger diameter, the result would be a much lower top speed. There's a sudden transition to higher speeds that occurs with raceboats/surfacing props that's not understood.



     
  2. sandhammaren05
    Joined: May 2009
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    Location: Texas & Austria

    sandhammaren05 Senior Member

    PS When the outfit is set up with a surfacing prop the cup certainly does not kill low speed performance. An uncupped prop will run very inefficiently at all planning speeds, low and high.
     
    DogCavalry likes this.
  3. brunello
    Joined: Jul 2008
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    Location: italy

    brunello Junior Member

    Do have a look at the "Surface propeller and low speed displacement boat " thread, you might find a lot of interesting (and different) opinions.
    We at Flexitab feel that surface propulsion is perfectly suitable for low speed vessels, this is why we tested a ship (clearly not the one mentioned by others in this thread) in the naples tank test, were surface props outperformed well-tuned submerged ones. (see pictures attached in the "Surface propeller and low speed displacement boat " thread).

    Regards, Brunello
     
  4. sandhammaren05
    Joined: May 2009
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    Location: Texas & Austria

    sandhammaren05 Senior Member

    PS
    Cup increases bow lift. Contrary to theory, which is pretty piecemeal, we do not run sq rt 2 more diameter with surfacing props in racing, we run the same diameter or less. I've wondered (naive question): for top speed with light load, is thrust the right parameter to maximize? I'm not sure. Thanks for the post!
     
    Last edited: Jan 21, 2010

  5. Simdrive
    Joined: Sep 2008
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    Simdrive New Member

    Yes, go to WWW.simplicity-marine.com they have been using there surface drives for tow boats and parasail boat for years.

    Alan
     
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