Trimaran project needs direction

Discussion in 'Multihulls' started by sailwisco, May 1, 2016.

  1. sailwisco
    Joined: May 2016
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    Location: Wisconsin

    sailwisco New Member

    First post in the forum so please bear with me. Building a trimaran that I am designing as I go... not ideal but thats the project. 3 questions that I would like to bounce off some other builders.

    Looking for some suggestions on building the cross beams/akas. Using some Hobie Cat 16 hulls as the amas.

    #1) Was hoping to use the stock Hobie cat "knuckles" to join the two. If I build wood akas, any ideas on a good way to attach the aluminum knuckle to the wood aka? The shape is unique(teardrop?) and I worry that it might be tough to mate the two snuggly.

    #2) Should I bother trying to make them fold? I have seen some simple designs that use a hinge on top or bottom but that might be too much hassle. Folding would decrease set-up time but likely increase construction? Whats the trade-off?

    #3) Aka construction. On my outrigger project, I laminated plywood to achieve the curved shape I was looking for. On this project, was thinking about a box construction. Suggestions?
  2. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    1) Go to
    2) buy a set of plans
    3) build to good plans

    If you don't know how to design good beam attachments then you won't be able to design a decent boat that holds together. Save a lot of time, effort, and money and use a good set of land to start with.
  3. tamas
    Joined: May 2009
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    Location: Brisbane

    tamas Junior Member

    Hi sailwisco, I started with a thought and got the job done ok, Plans are a good idea which I think will save you time in the end. I am not familiar with the hobie 16 knuckle but you can always glass extra pieces to stiffen. I have a blog at which might help. I opted for a folding system, I am glad I did, setup before sailing is very simple although it was a pain getting it to work well at the time of construction but that is made up at sailing time now. I have a flat bottom aka which works fine.

  4. jamez
    Joined: Feb 2007
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    Location: Auckland, New Zealand

    jamez Senior Member

  5. Skyak
    Joined: Jul 2012
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    Location: United States

    Skyak Senior Member

    I considered making a tri out of my hobie 3.5. I think it uses the same knuckles but each float only has about 200lb buoyancy. The problem I see for you is the limited contact area and section inside the knuckle. It is likely to be the weak link in your design if you limit yourself to the wood that can fit inside it. For the forces a 16 can generate I think you would be better off just connecting to the tubes sticking out of the float. Box section akas would be much lighter per stiffness -plywood verticals for shear, straight grain top and bottom.

    I am a fan of fast setup and trailering. Bolger said it best -boat use is inversely proportional to the amount of time it takes to get on the water.
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