Question about beam to length ratio on a catamaran

Discussion in 'Boat Design' started by Driedcacti, Apr 23, 2016.

  1. Driedcacti
    Joined: Apr 2016
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    Driedcacti New Member

    I want to learn how to calculate the beam to length ratio/coefficient. Is there a formula or a calculator?

    My second question is, what are the drawbacks of a catamaran with wide beam, for example as in shuttleworth's aerorig 52 or bandaloop or any other design that features a wide stance.
    Thank you,
  2. Richard Woods
    Joined: Jun 2006
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    Location: Back full time in the UK

    Richard Woods Woods Designs

    you have to differentiate between WL beam, centreline spacing, overall beam and LWL/LOA. It is the WL beam and CL spacing that are important.

    So the ratio you want is LWL/BWL, but better still would be the slenderness ratio, or displacement -length ratio

    I am one of the few designers to have experimented with varying the hull spacing on my own boats. I found no disadvantage when sailing with the wider beam, in fact I prefered it. That was 22ft WL and a 17ft overall beam, so it was wider than many trimarans (like the Telstar for example)

    The major disadvantages are finding somewhere to slip/haul/moor a wide boat. Extra weight (conversely more room).

    Also many early multihull builders had narrow sheds and that limited the beam they could build. But they couldn't tell the public that, so "invented" the fact that "wide boats are unseaworthy"

    You can read more on my website, try the FAQs page and Useful Articles sections

    Richard Woods of Woods Designs
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