beam stability

Discussion in 'Boat Design' started by amateurboater, Aug 8, 2015.

  1. amateurboater
    Joined: Jul 2015
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    Location: maine

    amateurboater New Member

    On a semi planing hull does excess beam cause instability in extreme weather conditions? The example we're using is a 46' Wesmac semi planing hull being built with a 17' 6" beam versus the standard 14' beam. I'm not saying the beam is excessive in this example but it seems to me at some point beam becomes excessive. Thanks for any feedback.
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    It would be necessary to analyze your boat, do some calculation to answer with some rigor but without more data that you have provided us, think that increasing beam, as a general rule, can, in some cases, decrease stability, it seems unlikely. Any additional information?
  3. amateurboater
    Joined: Jul 2015
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    amateurboater New Member

    Tansl- Many thanks for the reply to

  4. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I would not know on that size boat, nor exactly your intended use, but I do know on kayaks or canoes (should be similar for larger hulls I suspect), wider is more stable in calm conditions, and can carry more excess load. but the wider it gets, when in rough seas, the more it tends to get knocked around (a rough ride), though it is not really any more likely to capsize. It takes more skill in a narrow kayak, but it is more controllable in heavy seas.

    Seems to me a wider hull would come up on plane much easier on the same size and weight hull, but it will have more drag when in displacement mode. This means it would use more fuel per mile, and travel at a lower speed at the same throttle setting. but might get you there faster at intermediate speeds at higher throttle settings.

    You need to ask yourself why you want the additional width, and if the trade offs are worth it. It seems to me that the cost of building a boat that size, it would be money well spent to have someone how knows how check how the performance and ride will be affected before you spend all that money building it and find out it was a mistake.

    good luck.
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