Mast beam for large cat

Discussion in 'Wooden Boat Building and Restoration' started by windfiderthai, Nov 25, 2016.

  1. windfiderthai
    Joined: Nov 2016
    Posts: 3
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    Location: thailand

    windfiderthai New Member

    I have built several 50 foot aluminium catamarans using a multichine flat panel design.
    These boat where quite successful but the build process was difficult and expensive.
    I am considering changing the materials from alloy to cold molded mulichine ply to make it easier to build here in Thailand.

    My question to the forum is regarding the beams.
    The calcs for the bulkheads/stringers and hull skins are easy to work out but I cannot find any real reference books or info regarding the possible structure of the aft and main mast beams.
    I have an old copy of Roger Simpsons book which is full of great info ,,but not specific enough re the calculation's for the beams.
    The concept would be similar to Simpsons "truss beam" and "box beam" arrangements.

    In the alloy plans I used 6mm with vertical stiffening section every 200mm welded at 100mm centers ,,but how to make this in ply!!!!

    The calcs i have worked out so far are 12mm hull skins over 18mm ply bulkheads spaced at approx 1 mtr spacings with 40mm x 19mm dressed timber stringers at approximately 300mm centers all exoxied together with all items fully epoy sealed.
    This seems to be the basic scantlings as referenced from the Gougeon Brothers excellent book.
    Anyway I am rambling on now ,,
    would be great-full for any comments or assistance .
  2. messabout
    Joined: Jan 2006
    Posts: 3,272
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    Location: Lakeland Fl USA

    messabout Senior Member

    Windfiderthai, you are not being deliberately ignored by the members here. The question that you have asked is not at all clear. Just what do you wish to discuss? I take it that you are concerned with the cross beam design and construction. Is that the subject for discussion? A 50 foot cat will surely have cabin structure and other things that span the two hulls. That structure will play into the design possibilities.

    Cold molding of a multi chine boat is a puzzling description. Cold molding is usually done with curved sections, not flat panels..........Did you mean laminating?
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