displacement calculation help!

Discussion in 'Boat Design' started by schnaarf, May 31, 2008.

  1. schnaarf
    Joined: Nov 2007
    Posts: 5
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    Location: perth

    schnaarf Junior Member

    Hi, I'm having a bit of trouble with a couple of questions and was wandering if anyone here could help!

    I've got these figures:
    LWL - 15m
    BWL - 4m
    Sail Area - 120m2
    keel weight - 2.5 tonnes
    ballast ratio - 0.25
    SG (salt water) - 1.025

    and need to find:
    Displacement Length or Dimensional Slenderness ratio
    Non dimensional SA/(Vol of Displacement) ratio
    Length/Bredth ratio
    Ballast ratio

    If anyone could help me get started I'd be grateful!

  2. Guillermo
    Joined: Mar 2005
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    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

  3. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    Hi, Schnaarf.

    Here's what I came up with:

    1.) Displacement/Length---= 84.7*
    2.) Sail Area/Displacement = 25.9
    3.) Length/Breadth------- = 3.7 (LWL/0.85)/(WL Beam/0.85)

    * (2.5 mt Ballast)/(0.25 Ballast Ratio)=10 mt Displacement

    Length = 17.5 m
    Beam --= 4.7 m

    These are all really good guesses based on fairly typical contemporary design practices. The actual boat may be longer or shorter and the Beam might be greater.
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