Planing amas

Discussion in 'Hydrodynamics and Aerodynamics' started by Paul Scott, Sep 28, 2023.

  1. Paul Scott
    Joined: Sep 2004
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    Location: San Juan Island, Washington

    Paul Scott Senior Member


    Ok, brain is better, I thought I’d use some pics to illustrate thought process-

    to start with, the YouTube above, flat bottom hull mast forward, then:

    IMG_1456.jpeg

    Put those two together, so I’m sitting on the cross brace as hiking plank so I don’t need to hike out, and at two extremes, skinny stern:

    IMG_1455.jpeg

    Or fat stern

    IMG_1451.jpeg


    probably not with toothpicks for amas…:D

    the fat one will try to plane, maybe, but I’d have to deal with a moving center of float, cg, etc., so rails to move me longitudinally with smaller floats?

    the skinny one would, I think, require less movement fore and aft, maybe just rolling hips on the seat, and bigger floats?

    I have 2 rigs right now- 1). Mast forward (you tube) or 2) mast more in the middle (me)
    m IMG_0109.jpeg

    It’s a dipping lug…. (What could go wrong?)

    aside from the handling nightmare, the mast and plank could be one unit, which simplifies structure, makes moving the center of effort easier, and is located at the fat part of the hull.

    ^ indicates the outside parameters of where I’m at right now. Main hull doesn’t have to be a crease in the water, could be similar (that is flat) like the youTube hull seen here on her trailer:

    IMG_1023.jpeg


    I’ll wrangle up some cartoons.

    here is link to a great discussion about mini sailing canoe amas that I found really helpful (and corroborated another boat I did with 4’ by 4” by 4” amas-What can I say, I had a cello instructor who said I liked reinventing the wheel:)) :

    Mini outriggers - Open Canoe Sailing Group | Sailing Adventures https://www.ocsg.org.uk/sailing-canoes/mini-outriggers/
     
    Last edited: Sep 30, 2023
  2. Paul Scott
    Joined: Sep 2004
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    Location: San Juan Island, Washington

    Paul Scott Senior Member

    image.jpg Cartoon with dipping lug
     
  3. Paul Scott
    Joined: Sep 2004
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    Location: San Juan Island, Washington

    Paul Scott Senior Member

    Actually, this would be just the start if I were to commission another design with a naval architect…. It’s just part of the fun- Amati was supposed to be like a Jaguar XJ6- power, speed, and elegance: there was lots more……
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    May I suggest, given all the above, just have fun!

    Build various options to see what works and doesn't work.
    This way it is fun trying and fun learning...rather than going straight to a "solution" based upon numbers.

    It is a great way to have fun experimenting and learning lots about your own boat's abilities!
     
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  5. Paul Scott
    Joined: Sep 2004
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    Location: San Juan Island, Washington

    Paul Scott Senior Member

    It’s like stomp boxes and electric guitars, er, electric cellos- it’s an expensive but satisfying way to find yourself…:cool:

    That said, any rules of thumb?
     
  6. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    There are, but most likely not really applicable for this application.

    That said. Make a simple outrigger (ama) that is say 10% of the weight/displacement of your boat.
    Then make just one outrigger at 10%...place this on a simple pole/frame work. So it is rather like a Proa.

    Then simply by inducing a roll, by moving to either side of the boat....gauge the behaviour of the boat.
    Does 10% in a single ama, provide you with enough "stability" to feel - yeah, that's ok.
    If so, then split it, so you have 5% in each ama, to be a tri....conduct the same test again.

    Keep going until you find the right "balance" you are looking for, or rather - feel for....so 5% or 10% or 20% etc.

    Once that is done, experiment with the long.t location. By moving it from midships, fwd by 10% of the length, then 20% of the length fwd, and repeat aft.

    This way, you'll end up with a simple matrix of cause and effect...i.e the most "optimal" size and location of your ama.

    It will be fun experimenting and try these different options, and learning a lot about your boat too.
     
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  7. Paul Scott
    Joined: Sep 2004
    Posts: 623
    Likes: 118, Points: 43, Legacy Rep: 84
    Location: San Juan Island, Washington

    Paul Scott Senior Member

    Excellent- Cheap, cheerful and effective! Now if I could just learn the Jim Brown method of hand testing multihull models in a pool. Without building a tonne of waterproof models…. It just occurred to ask how many NA’s build models? Let’s see… Irens, Herreschoff….?….
     
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  8. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Last edited: Oct 1, 2023
    Paul Scott likes this.
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