Extended steel hull advice please

Discussion in 'Stability' started by auspain, Aug 7, 2010.

  1. auspain
    Joined: Aug 2010
    Posts: 3
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    Location: Australia

    auspain New Member

    I would like advice please on the extension of a yacht I want to buy.

    Its a 38 Boro Steel Ketch, with an added step down stern to make it a 40.

    Two things concern: 1st it appears to have a small keel for its size and I wonder about its self righting ability? Second, with the extended stern how it will sit in the water and what affect it may have on the yacht?
    Pictures are here.
    [​IMG]
     
  2. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    Depending on the steel thickness of the mod, it will be lower at the stern than it's current trim by I'd guess around 200 mm.
    You may need to add trimmer ballast up forward and if you want the same initial stiffness in the hull (stability) you'll need to add ballast to the keel or just deepen it by 100mm or so. This compensates for the trimmer ballast and the extra steel.
    The designer has died so it's going to be trial and error.

    It's Ok if its cheap, you might even find it sails quite well on it's new longer waterline without any ballast changes. As a rough guide as soon as it's in the water you'll usually see just from walking from side to side a few times in sync with the roll period how tender or stiff the vessel is. Without the data there's no way of properly assessing this on the hard.
     
  3. auspain
    Joined: Aug 2010
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    auspain New Member

    Thank you Mike for your reply, very help full. The yacht needs some interior work and electronics, due to a small fire.
     
  4. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    That would require a survey.
    If it's near Hobart I'd be able to take a quick look at it for you for free.
     

  5. auspain
    Joined: Aug 2010
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    Location: Australia

    auspain New Member

    Not close. Thank you kindly for the offer.
     
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