Looking for help determine speed and power requirements of potential power catamaran

Discussion in 'Hydrodynamics and Aerodynamics' started by massandspace, Nov 8, 2017.

  1. massandspace
    Joined: Sep 2017
    Posts: 33
    Likes: 0, Points: 6
    Location: Salt Chuck

    massandspace Junior Member

    All good people.

    I have read, re-read and read again all the posts and will try to smooth out my interpretation of all the various inputs, just as the hulls in the Rhino model needed smoothing.

    My basic question, again, if anyone wants one final stab at it:

    If I mount two (2) 15 or 20hp motors on the hulls in question what will happen? I did some actual water tests with two 8 hp motors and the boat seemed to bog down when fully throttled. Is it worth my time to test 2 more larger motors? I am looking for at least 10 knots of speed in flat water. ..if not a bit more...with that setup.

    Gracias!
     
  2. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    Although each one of us who have studied your question we have arrived at very different results, in all three cases it seems clear that with 20 hp you will be able to reach 8 to 10 knots.
    De nada!
     
  3. Ad Hoc
    Joined: Oct 2008
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    Likes: 451, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Thats because of 2 main reasons.

    1) The main prismatic hump of the resistance for your boat occurs at around 7-8knots. This means the greatest resistance and also, all vessel will squat/trim while going through this transition phase (if that is the intention).

    2) Because you wish to go faster than this, with more power, your hull shape will not allow it, well not without massive amounts more power for a small increase in speed. You need to alter your aft shape to allow the water flow to "cut-off"...so not going to a taper/point. But square and flat-ish.
     

  4. TANSL
    Joined: Sep 2011
    Posts: 5,923
    Likes: 239, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    This whole question could be given two different approaches:
    1ยบ.- What can I do with the hulls and the engine I have?
    2nd.- What should I change to, for example, get a speed of 15 knots ?.

    For the second approach I think you should think of a totally different hull.
     
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