Sailboat Beam and Performances

Discussion in 'Sailboats' started by Triman, Sep 16, 2007.

  1. Triman
    Joined: Aug 2007
    Posts: 10
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    Location: Switzerland

    Triman Junior Member

    Hy to all;
    I have a question about the beam of a sailboat and his effect on overall performances: in the last years we can see very different design concepts about sailboats: from the very wide hulls (Minitransat-IMOCA 60') to the very narrow ones (Esse 850, AC). Of course, they may have different pourposes (ocean sailing v/s club racing), but if we think about a small allround sailboat (ab. 8m - 27') with some accomodations, on a modern hull design, how will the overall beam affect performances and seaworthiness? On that size range, assumed the boat is well designed and built, are the performace differences between a 2,55m hull (still trailerable) and a wider hull (2,80 - 3m) really significant?
    Many thank for your answers;
    Good Wind
  2. Stephen Ditmore
    Joined: Jun 2001
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    Location: Smithtown, New York, USA

    Stephen Ditmore Senior Member

    Beam helps stability at the heel angles boats typically sail, especially where it impacts how much people or other forms of movable ballast can be located to windward to contribute to stability. Beam therefore influences how much sail area the boat can effectively carry (if you know righting moment at 30 degrees you can make an initial estimate of recommended sail area based on one pound of pressure per square foot of sail). Beam does not typically help stability at 80 degrees or more, which is what is needed for safety in potentially catastrophic situations. In the case of the size range you're talking about light weight and wide generally equals fast, but for the formula to work in your favor your MUST keep it light, and your boat's ability to self right will require the center of gravity be kept low (which means carrying ballast).

    There are plenty of examples of good narrow boats, such as the Etchells 22 and the Wylie Wabbit, in that size range - so either can approach can work, as you suggest.

    My feeling is that the max trailerable beam will work just fine as long as you keep the hull, deck, and rig light, the ballast low, the crew weight to windward, and the sail area appropriate (which can be determined once stability can be calculated). Some form of wings or racks, such as this boat has:
    might help quite a bit if you have either signif. crew weight to windward or water ballast in the windward wing.
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