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Thread: Hull shape

  1. #1
    Join Date
    Aug 2003
    Location
    Canada
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    920

    Default Hull shape

    I have heard that a flattish aft section makes a boat go downwind better. Can anyone explain why? In laymans terms?
    Thanks
    Don
    Don Case
    Vancouver Island

  2. #2
    Join Date
    Aug 2003
    Location
    Minnesota USA
    Posts
    3,811

    Default Re: Hull shape

    I'll take a stab ---- flat underwater sections promote/encouage the boat to plane (rise up and hopefully on top of the hull displacement wave) where there can be a bit more speed. Since many off-shore races are or have long downwind legs, hulls for the round-the-world events are optimized for off-wind sailing. Once up on a plane, hopefully the hull will trave at the true speed of the wind. Boats with less hull weight or displacment (multihulls, skiffs, scows, etc.) need less of the flat large sections, and can often EXCEED the wind in broad reaching legs. (ice boats and land yachts can do same "upwind" in some conditions and the right wind directions - creating their own apparent wind.)

    I'm sure others will assist in explanation/theory.

  3. #3
    Join Date
    Apr 2005
    Location
    Toulouse (Fra)
    Posts
    3,288

    Default Re: Hull shape

    This is what I knows about flat bottom hulls.
    I just prepared a little sketch with few words :



    Uploaded with ImageShack.us

    ClaudioD
    Last edited by claudio; 12-23-2010 at 05:16 PM.

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