changing the shape of the boat

Discussion in 'Sailboats' started by tamkvaitis, Jan 3, 2007.

  1. Vega
    Joined: Apr 2005
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    Vega Senior Member

    Thanks Doug, interesting stuff.
    A safety feature, preserving the boat in bad weather while running (bow up) and allowing more freedom on the design, optimizing planning in good weather (bow down). We will see if it works;)
     

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  2. Guillermo
    Joined: Mar 2005
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    Guillermo Ingeniero Naval

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  3. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Howdy,

    This is not right.

    Bethwaite boats show quite the opposite - that was their breakthrough.

    Before Julian built his skiff moth derived Prime 18 footers everyone was trying to get as much "planing surface" as possible.

    Julian went completely the other way with boats of much less surface area that require much less sail area to sail at much better speeds.

    The other areas the boats were improved were a much lower rocker - which would normally mean that the transom would drag - but in this case the transom is much narrower and the crew move forward anyhow until the dynamic lift is enough to get the bow up.

    Also instead of the flat sections being all at the back of the boat (we all thought the boat planed on the back - didn't we :) - we used to all design the backs of our boats to go upwind and the bows veed to go upwind, Julian subverted that by having a much flatter but narrow section right though the body of the boat by choosing a more "parabolic" section for the bow - though I think Michael Nash may have been heading in that direction already with his NS14 designs.

    Nope - big wide sterns are slow on average - the bethwaite boats don't have them.

    Michael Storer
     
  4. Vega
    Joined: Apr 2005
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    Vega Senior Member

    On a 60ft boat having as crew a lonely skipper I believe that he would have difficulty in doing that.
     
  5. Ramona
    Joined: Feb 2007
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    Ramona Senior Member

    The Bethwaites could have saved a lot of time by just studying the lines of a Finn dinghy. How could a hull designed in about 1936 be so right. Hull forms like the NS14, early moths etc. "jump" on to the plane, the Finn merely goes faster as it goes from displacement to planing mode.
     

  6. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    The Finn is a very wonderful boat - so I partially agree - but the modes are quite different - you just need to look at the bow wave of a Finn to see the difference.

    Any wave or spray created by the boat is drag - and the Finn does have a big big spray pattern up front when she is going.

    The NS14 doesn't. And neither NS14 or Finn have the high speed angle quite as well sorted asthe 18 - though the NS is closer if you look at the bottom shapes.
     
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