Prop Efficiency in Reverse

Discussion in 'Props' started by phillip, May 1, 2005.

  1. phillip
    Joined: Apr 2005
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    Location: sault ste. marie ont. canada

    phillip Junior Member

    Manoeuvring a 24' sloop under auxiliary power with through hub exhaust. Would changing the number of blades improve the prop. efficiency when climbing through the exhaust in reverse?
    I read the thread discussing reventing of exhaust by racers and wonder if there is an application here or would a simple prop change do the job.

    Thanks
    Phil
     
  2. cyclops
    Joined: Feb 2005
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    Location: usa

    cyclops Senior Member

    I am going to apply logic to this one. A 1/2 blade prop has the greatest diameter. A 5 blade prop 25% approx. smaller dia.. Therefore the more blades the greater the chance of exhaust bubbles disturbing the prop flow and causing some loss of eff. How much in either diriction is up to a empirical testing of bollard pull, speed and turn diameter. My best shot.
     
  3. phillip
    Joined: Apr 2005
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    Location: sault ste. marie ont. canada

    phillip Junior Member

    So are you thinking 2 blade>larger diameter> match the pitch on the 3 blade. The 2 blade same rpm might pull more useable water out of the thrust zone?(If that's what you call it?)

    Thanks Phil
     

  4. cyclops
    Joined: Feb 2005
    Posts: 1,059
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    Location: usa

    cyclops Senior Member

    In theory, yes. In practice, lower the motor or get a bigger one to better control the boat.
     
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