Is This True

Discussion in 'Boat Design' started by matt76, Jun 7, 2007.

  1. matt76
    Joined: Jun 2007
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    Location: st. louis missouri

    matt76 Junior Member

  2. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    Is there a scale or formula that equates #s of thrust to HP? If so, then I guess you can metreculate.
    But if it is possible to create thrust through gear ratios, then it becomes a marketing game.
    Better way to compare would be a SAE ratingm To me, I would want to know the discharge rate, speed @ ? RPM and "perfomance data.
  3. Guest625101138

    Guest625101138 Previous Member

    Thrust does not mean much unless you want a tug boat. Thrust gets down to grip in the water not so much HP. Big diameter prop will give better grip and more thrust for the HP if it is pitched right.

    To get the best from the HP you need to match the prop to the application.

    Rick W.

  4. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    They are talking bollard conditions here and there is a lot of hype and a little smoke and mirrors.

    A B-series propeller produces ~35 lbs of thrust per shp at bollard wether it is 3" in diameter or 25'

    A Kaplan prop in a well designed nozzle produces ~40-50 lbs of thrust per shp at bollard depending on tip conditions. I have designed a Kaplan that has produced 65 lbs of thrust per shp in at bollard. But better results are acchieved with open water props.

    I have also designed a set of counter-rotating props that achieved 215 lbs of thrust with 0.75 shp in. It's just a game you can play depending on how you set up your design conditions.

    Like Rick said, the more important point is designing for your operating point, not some numbers game for ads.
    Last edited: Jun 7, 2007
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