How to know if a design's righting moment is enough?

Discussion in 'Stability' started by PhilippeCE, Apr 16, 2022.

  1. PhilippeCE
    Joined: Apr 2022
    Posts: 20
    Likes: 4, Points: 3
    Location: Montreal, Quebec, Canada

    PhilippeCE Junior Member

    BlueBell likes this.
  2. AlanX
    Joined: Mar 2022
    Posts: 113
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    Location: Perth, Western Australia

    AlanX Senior Member

    I did that, It capsized the first outing, had to add ballast:
    76.jpg

    Worth the effort to realise you have too much sail area.

    It righted easily (builtin water tight bulkheads) but very sore after bailing out a tonne or so of water.

    AlanX
     
    PhilippeCE and BlueBell like this.
  3. PhilippeCE
    Joined: Apr 2022
    Posts: 20
    Likes: 4, Points: 3
    Location: Montreal, Quebec, Canada

    PhilippeCE Junior Member

  4. AlanX
    Joined: Mar 2022
    Posts: 113
    Likes: 20, Points: 28
    Location: Perth, Western Australia

    AlanX Senior Member

  5. PhilippeCE
    Joined: Apr 2022
    Posts: 20
    Likes: 4, Points: 3
    Location: Montreal, Quebec, Canada

    PhilippeCE Junior Member

    @AlanX maybe it would have been more stable if you would have kept the width all the way aft. but that would have changed the style of it.
     
  6. AlanX
    Joined: Mar 2022
    Posts: 113
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    Location: Perth, Western Australia

    AlanX Senior Member

    @PhilippeCE,

    The far aft section adds little to the righting moment as if has (relatively) little displacement.
    Having said that I would not do a double ended boat again (except for a small cat pontoon or canoe).
    But I am still a fan of the flatiron/sharpie hull shape:
    18' sharpie 6-7-2013 2-45-14 PM.jpg

    Basically, you set boat's balance by setting the bow/stem just in the water.
    As the boat is loaded, the aft/stern just sits lower.
    When heeled, the hull presents a "V" to the water flow.

    Here is a pontoon/catamaran version:
    FlatIronpontoon.png

    Regards AlanX
     

  7. BlueBell
    Joined: May 2017
    Posts: 2,116
    Likes: 651, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . . .

    100% accurate, easy, cheap, instant and reliable results.
    A formula, hah. Hands on engineering is the way to go.
    And what a learning experience!
    Way to go AlanX.
     
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