16ft beach cat design advice

Discussion in 'Multihulls' started by ch3oh, Mar 9, 2015.

  1. teamvmg
    Joined: May 2008
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    Location: christchurch,uk

    teamvmg Senior Member

    That drawing would have confused an idiot wouldn't it?
    Oh - I'll get me coat!
     
  2. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    We made her stretch to the very opposite, 1300mm wide.. Glassed those seams over with 300gsm 50mm tape. Timber is 20x20 spruce on deck edges, 20x15 mid-sheet. Should I go for ply dagger trunks and boards with a square top section or option 2: foil-shaped boards top to bottom and use them as moulds for glass trunks? I'm thinking square, as it would be easier to experiment with different foil profiles and spans?
     

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  3. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    Last night we managed to steam bend the first hull to a deck jig. What a pita, but worked out eventually. My mate made a steaming unit out of a compressor air tank heated by a ring burner. There was a 8 bar safety valve and we hit a steady 2 bar while the steam was running. A hydraulic hose delivered the goods into a plastic tent with wet towels against the hull skin. Lines came out great, there's about 80mm of rocker and enough volyme to carry a case of extra beer per crew member.
    I noted that the hobie front beam was cracked underside, starting from the dolphin striker hole. I managed to source some 60x3 60xx T6 round tube freebies and decided to build new beams. Their stiffness is my main concern- a quick math says they are only 58% the stiffness of 80x2 tube recommended for the blade. Then again a mosquito flies hull with 50x39x3 square beams :rolleyes:
    Today we'll measure the hull form and fine-tune the bulkhead lines to what the ply wants to bend into.
     
  4. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    We pulled hull #1 out of the jig without decking. A bit risky since id doesn't yet posess full torsional stiffness but since it's a one off prototype thingy its easier to have some play. Then we bent #2 in without breaking the bow like on the first one. 3 bulkheads glassed in, of which 2 are H shaped douple ones for beam landings. Rest will be 20mm foam.
     

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  5. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    It's about time for an update. The first (port) hull has all the stuff inside. Chainplates are made of 0,8mm stainless and laminated between 3 layers of plywood. Daggerboard boxes are 4mm ply with 12mm ply reinforcements. They are glued in with triangular wood strips to add surface area and held sideways by strips of wood. There's 7 foam semi bulkheads that we intend to cut to deck shape with a hot wire cutter.
     

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