Catamaran Trampoline Length as a Fraction of Boat Length?

Discussion in 'Boat Design' started by Iridian, Jun 15, 2021.

  1. Iridian
    Joined: Jan 2020
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    Location: MD

    Iridian Junior Member

    I know this question may be a bit hard to answer as it's likely dependent on hull shape, weight, wave piercing vs non-wave piercing bows, and height of the trampoline, but in general, what fraction of the total boat length should be devoted to the trampoline to sufficiently avoid waves crashing over top of the deck and minimize slamming? Assume standard bridge deck clearance.

    Recognize that the perfect solution would have no deck, and the entire thing would be a trampoline, but that's not exactly viable.

    For example, the Ed Horstman 55' has a really short trampoline:

    [​IMG]

    As does the Bruce Roberts Eurocat 1500:

    [​IMG]

    In contrast, the Schionning Arrow has substantially more trampoline length:

    [​IMG]

    And the Balance 526 takes the cake with a massive trampoline:
    [​IMG]

    How much trampoline is enough?
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    My boat is 32' waterline and has about 3' trampoline, which is about 10%...

    I have seen some boats with massive trampolines, but don't see the point unless they are trading it for weight. A tramp is lighter than any hard option.
     
  3. Iridian
    Joined: Jan 2020
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    Location: MD

    Iridian Junior Member

    What sort of bows does your boat have? If you have wave piercing bows I'd expect it probably has to be substantially longer than something with more buoyant bows.
     
  4. fallguy
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    fallguy Senior Member

    Wave piercers.. canoe hulls... Richard Woods design

    Another thing is the tramp can be holes or mesh and so the choice of material would affect slamming in the rough stuff...
     
  5. fallguy
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    fallguy Senior Member

  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I would say each of the boats you pictured would have different propensity to pitch. Perhaps, and I am only guessing, the boat with the most net is the least likely, but I could be wrong. This is at least a conversation starter and well beyond my cv in accounting!
     

  7. Tony.Ellen
    Joined: Nov 2019
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    Location: Sweden

    Tony.Ellen Junior Member

    A good article with some figures to start from.

     

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