Model Boat Design

Discussion in 'Boat Design' started by sail fast, Apr 28, 2010.

  1. sail fast
    Joined: Apr 2010
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    sail fast Junior Member

    I am in the process of making modifications to an existing design and need info on righting moment formula. I need to reduce total weight by at least 2.5 lbs. and can do so by lengthining(sp) the keel.This will shorten the waterline length.
    sail fast
     
  2. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

  3. Paul Kotzebue

    Paul Kotzebue Previous Member

    If you're changing length, weight, and keel depth, finding an equivalent righting moment (which changes with heel angle) is much more than applying a formula.

    I suggest getting a copy of "Principles of Yacht Design" and read the chapters on hydrostatics and stability. You're going to need to do some research.
     
  4. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ====================
    Is that on a 36/600? That will be hard to do-especially if yours is already one of the light boats at around 5-6lb! I'd suggest a new design with the max wl length and narrowest hull possible. I don't remember: is movable ballast still illegal? Thats one solution but it would make a boat that would require more channels and lots of practice to sail well-but it would be a rocket.
    Again, in the old days(10 years ago) light boats were around 5-6lbs with an 80% B/D ratio-4-to 4.8lbs of ballast. Losing 2.5lbs from a boat like that will be tough-and likely impossible without either a wildly deep keel or movable ballast. We can guesstimate how deep the keel has to be for a skinny 36-to lose that much weight and have the same RM would probably require an 18" keel going to 36". If I were you I'd contact Lester Gilbert or Graham Bantock and see if their research has revealed negatives other than the obvious ones for that kind of keel length on a 36" hull. Both those guys were helpful to me in the old days.
    Good Luck!
     
  5. sail fast
    Joined: Apr 2010
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    sail fast Junior Member

    The boat I need to loose weight on is a Pointing 36 by Amen, it is a 9.5 lb boat and looks like a Mistral by Bob DeBow. The Keel is a good 6" shorter than my CF TalonII which is less than 5lbs.
    Sail Fast
     

  6. sail fast
    Joined: Apr 2010
    Posts: 6
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    Location: Arizona

    sail fast Junior Member

    Model Boats

    My name is sailfast and by this website you are a model bouider, are they AMYA Class boats? I have been building and sailing them since 1991 and in 1944 sailed those that were equiped with steerimg vanes.

    sail fast
     
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