Effective power to Horsepower

Discussion in 'Multihulls' started by AJP, Aug 8, 2019.

  1. AJP
    Joined: Jul 2019
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    Location: India

    AJP New Member

    Hi All,

    A good day to you, I recently developed a design and calculated the overall resistance and powering required through CFD, I would like to know how do we arrive at Horsepower required if we have the total effective power, also the same will be OBM powered.

    Thanks,
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It might be better if you show the design you have created.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Is OBM outboard motor ?
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    This is what is called the PC or propulsive coefficient. Where PC = ehp/shp.
    The ehp you have the shp you don't, as that is what you're trying to find. So this means what is your PC?

    PC is defined as = appendage coef x hull efficiency x prop efficiency x relative rotative efficiency x transmission efficiency.

    In other words, all the element in the "system". We can ame 'best guesses' based upon the layout of the shafting and prop relative to the hull the shaft angle etc etc. The PC for most vessel range from 0.40 - 0.65.
    If you have a conventional outboard and it is mounted conventionally, then the PC averages around 0.50.

    So if your ehp says you need 500kW the actual installed power you need the shp, is - yup - 1000kW.
     
  5. AJP
    Joined: Jul 2019
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    Location: India

    AJP New Member

    Thank you so much for your reply,certainly what i was looking for & it would be really helpful if you could join for further discussions
     
    Last edited: Aug 8, 2019

  6. AJP
    Joined: Jul 2019
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    Location: India

    AJP New Member

    Mr. efficinecy, Thankyou for your reply, and yes what I meant from OBM was outboard Motor and also the design is for a 50 Ft fishing catamaran, shall attach a file after i'm done with the preliminary general arrangement plan. Looking forward for more conversations on the same.
     
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