24 ft Proa Design

Discussion in 'Multihulls' started by Jacobra, Nov 21, 2020.

  1. Jacobra
    Joined: May 2017
    Posts: 2
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    Location: Seattle

    Jacobra New Member

    Hi all, I have been working on a pacific proa camp cruising design to recycle a hobie 16 rig. I don't have it completely modelled but it’s worked out far enough to get the idea.
    The hull shape is based around seating ergonomics which give the main hull it’s flair, and a self bailing floor ~4 inches above the waterline. Below the waterline are semicircular hull sections with 18.5” waterline beam. Steering will be done through Newick style dagger rudders. The ama rotates up and over for trailering sorta like Richard Woods’ Strike trimarans. Auxiliary power will be an outboard mounted to one of the main beams.
    Designed displacement is 1,000 lbs and the self bailing floor goes awash at 1,850 lbs assuming the ama sinks evenly.

    Construction is strip built and fiberglassed with plywood bulkheads and decks. Preliminary weight estimates show that if I’m lucky I can keep it around 500lbs.

    Any thoughts on the design so far?
  2. BlueBell
    Joined: May 2017
    Posts: 1,682
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    Location: Victoria BC Canada

    BlueBell "Whatever..."

    I think it looks great!

    Why would you calculate it including the sealed ama?
    Remove the ama from self-bailing vs floor-awash calculation.
  3. garydierking
    Joined: Sep 2004
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    Location: New Zealand

    garydierking Senior Member

    Are you using the dagger rudders for all of your lateral resistance? No daggerboard through the ama?
    Manfred.pech likes this.
  4. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    I love the shapes, but to build them will require a high skill level and many more hours of labour, if it's a labour of love thats fine. I assume the design is a one off for own satisfaction ? If you intend to sell plans then be prepared to be asked for a sheet ply version.

  5. Jacobra
    Joined: May 2017
    Posts: 2
    Likes: 0, Points: 1
    Location: Seattle

    Jacobra New Member

    That's a fair point, I was thinking of it as max weight with reasonable weight distribution when in reality additional load would likely be in the main hull. Unfortunately I forgot to add the ama to that figure so they are actually as follows:
    Main hull loaded to floor level with ama at designed displacement - 1,850 lbs
    Main hull loaded to floor level with ama remaining level - 2,176 lbs

    My current plan is to only use the dagger rudders for lateral resistance, but it's probably worth building a case into the ama anyways. I just don't like the idea of going all the way out to the ama to raise or lower the board. Seems like a pain when beaching and makes it harder to adjust center of lateral resistance while underway.

    Thank you, this is planned for a self build only. I expect it will take more time both in hull construction and fit out, but I think the curves will pay off with more motivation to finish the project. :)
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