Seeking a textbook on multihull structural forces

Discussion in 'Multihulls' started by nacrajon, Oct 13, 2014.

  1. nacrajon
    Joined: Jan 2009
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    Location: Australia

    nacrajon Junior Member

    I thinking about replacing the beams on my 21 ft demountable tri to gain a wider beam and more righting moment.

    Is there a reference text around that I could buy as I want to double check my structural calcs and ensure my assumptions are correct.

    Any recommendations?
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    See what they say about this issue any Classification Society regulations or the ISO 12215 standard.
  3. oldsailor7
    Joined: May 2008
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    oldsailor7 Senior Member

    What do your existing beams, (Akas), look like.?
  4. nacrajon
    Joined: Jan 2009
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    nacrajon Junior Member

    Boat is a Virus Magnum 21 classic, I want to convert it to S spec. Beam would change from 4m to 4.8m. Demountable tri, alloy mast extrusion with 81mm ID across the main hull. Cross beams slide in with 80mm OD and from memory 2mm wall thickness.
    I can only get 5000 series 80mm tubing in Australia or go carbon at significant expense. There is approximately 0.5m that is telescoped and held in place with a retaining pin. Floats are clamped with a saddle.

    I've got a non standard 22m gennaker and longer rudder and improved centre board.

    This boat has been in the Bass Straight for the last two weekends sailing so I'm looking for reliability, not ultimate light weight.

    Manufacturer has gone bust so I can't buy the parts over the counter, I will reverse engineer it.
    Last edited: Oct 13, 2014
  5. Alik
    Joined: Jul 2003
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    Alik Senior Member

    Well ,You have to re-calculate the rig as well. It is not likely to be designed for increased righting moment. So, You would need a book on rig design as well :)
  6. Richard Woods
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    Richard Woods Woods Designs


    Richard Woods

  7. cmckesson
    Joined: Jun 2008
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    cmckesson Naval Architect

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