Leeboards: professional or 'have a go'?

Discussion in 'Hydrodynamics and Aerodynamics' started by Graemecb1971, Jul 2, 2022.

  1. Graemecb1971
    Joined: Jul 2022
    Posts: 20
    Likes: 2, Points: 3
    Location: Uk

    Graemecb1971 Junior Member

    Thank you: no. Is there a program for that? I'm the recent owner, not the designer or builder.
    Science and IT background yes, boats and boating Nil . Bought the barge as my house and this is my version of DIY improvements.

    Again, this forum and the participants are fantastic!
     
  2. Flotation
    Joined: Jan 2020
    Posts: 175
    Likes: 35, Points: 28
    Location: Canada

    Flotation Senior Member

    In addition to the other helpful comments, typical leeboards pivot around a bolt. That same bolt also allows for some sideways movement of the leeboard. This will for a large part prevent them from helping against roll motion but will give you leeboards slapping against your hull when rolling. Do not recommend.
     
  3. Graemecb1971
    Joined: Jul 2022
    Posts: 20
    Likes: 2, Points: 3
    Location: Uk

    Graemecb1971 Junior Member

    Thank you; Good point
     
  4. Robert Biegler
    Joined: Jun 2017
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    Location: Trondheim

    Robert Biegler Senior Member

    What is your roll period? Generally high stability and low rotational inertia give you a short roll period, while low stability and high rotational inertia give a long roll period. Lacking a mast, your vessel should have relatively low rotational inertia. So if you have a long roll period, you have low stability. That even a moderate breeze gives you trouble suggests your problem is lack of stability more than lack of roll damping. Then extra windage could be dangerous unless you also increase stability, and that makes this a problem for professionals.

    I have seen the rule of thumb that the roll period in seconds should not be more than the beam of the vessel in metres. And I found a thread on the subject: Roll period https://www.boatdesign.net/threads/roll-period.46271/
     
  5. Graemecb1971
    Joined: Jul 2022
    Posts: 20
    Likes: 2, Points: 3
    Location: Uk

    Graemecb1971 Junior Member

    Thank you; I'll time the roll period next time we get any breeze.
    At this point I'm considering adding a few tonnes of ballast in the bilge.
    4t of water moved from bow to midships raised the bow by 20cm, so I'm guessing I can get away with 2t strategically placed along port areas of the bilge (we list slightly starboard as it is) and increase the draft just a few cm.
    I'll read the article a bit later too and wait for a breezy day
     

  6. Graemecb1971
    Joined: Jul 2022
    Posts: 20
    Likes: 2, Points: 3
    Location: Uk

    Graemecb1971 Junior Member

    Thank you to everyone for commenting and providing so much helpful advice.

    I'll freeze this thread now if that is OK. I've got a lot of reading to do and I think, thanks to advice on stability throughout this thread, that leeboards are not the solution but rather I should try and stabilise and balance her first.
    Again, many thanks
     
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