ama design and daggerboard placement

Discussion in 'Multihulls' started by olsurfer, Mar 6, 2017.

  1. olsurfer
    Joined: Mar 2015
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    olsurfer Junior Member

    I've searched threads here and SA but haven't found a source that covers the trend towards high percentage bouyancy in the amas and how it is distributed in the ama shape. I see amas that are almost pintails and others that have almost no taper towards the stern and end with a bigger cross-section. Also some have v bottoms while others have a much flatter run. I'm also interested in having daggerboards in the amas which opens up a whole other can of worms in terms of symetrical or asymetrical, canted or not and location of the daggerboards in the ama in relation to the mast (behind-even with-in front of). Where can I find a book or any recent design info that will help me with this? Thanks
     
  2. Doug Lord
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    Doug Lord Flight Ready

    ama design and placement

    How long and how wide is the boat?
     
  3. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    You can read up on Tony Grainger's thoughts here.

    https://www.graingerdesigns.net/the-lab/new-floats-for-the-pickle-forks/

    Floats with canoe sterns have some problems with squatting upwind so are generally less favored these days. So it's a balance you want buoyancy fairly low down to reduce heel but not so low that the float slams and you want the bows to be able to shed water easily.

    As a rule of thumb you want your daggerboard to be in the middle of the balanced sail area wherever that happens to be. On a trimaran you can position the mast well back if you like as long as you adjust the volume of the main hull to trim appropriately.
     
  4. olsurfer
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    olsurfer Junior Member

    length - 30ft beam - 24ft.
     
  5. Doug Lord
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    Doug Lord Flight Ready

  6. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    Shuttleworth's Multihull Design Considerations for Seaworthiness and Reflections on the design of Brittany Ferries G.B. have good discussions of stability indices and shaping amas to control the movement of the center of buoyancy as the loads change.
     

  7. olsurfer
    Joined: Mar 2015
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    olsurfer Junior Member

    Thanks tspeer, I knew of the Shuttleworthdesign (multihull design considerations) and thanks for the other link! I really fell for a Shuttleworth tri that was for sale down in Mexico but was destroyed and grounded from a hurricane just as we were starting to work out a deal. Broke my heart, such a beautiful tri gone in a heartbeat!
     
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