Help needed- metacentric height and other restrictions

Discussion in 'Boat Design' started by Alfonso, Dec 4, 2010.

  1. Alfonso
    Joined: Sep 2008
    Posts: 40
    Likes: 2, Points: 0, Legacy Rep: 68
    Location: Croatia

    Alfonso Junior Member

    First I want to apologize myself for copy-pasting this tread. I know that is not popular.... But since I haven't got any replies in ''Stability forum'', I pasted it here, hoping that more people could read this and try to help.

    In advance, thank You for Your time!

    I need some literature or formulas that would help me to exclude some of generated projects due to stability criteria.
    I know there are regulations for minimal metacentric height, but what is with maximum?? There is a formula that says:


    T-roll period (min. some 7-12 sec)

    and you can give roll period that You want, but it does not suits me. Because, for the same ship I get GMmin=0,3m and GMmax=0,39 (for roll period 8 sec)???

    Is there any criteria for minimum KM, or BM.... Or something like that??

    Type of ship is: fishing vessel

    Thank you
  2. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    One reason for lack of replies, is that your question is not clear. Secondly, if you are reviewing/designing a vessel, in this case a fishing vessel, that is required to satisfy stability criteria, then you just follow the rules given to ensure the design satisfy that which is required. There is no magic.

    I suspect that you are either a student, or working in a company that offers no assistance to gradutes or something similar.

    You should read the attached paper. It will give you the answer to all your questions.

    Attached Files:

  3. Alfonso
    Joined: Sep 2008
    Posts: 40
    Likes: 2, Points: 0, Legacy Rep: 68
    Location: Croatia

    Alfonso Junior Member

    Ad Hoc

    Yes, I might have been a little unclear. I'm working on a simple software which would generate a large number of ''project ships'' given main dimensions, their ratios and step. Lets say that You give:

    Lmin=20m, Lmax=40m, step 0,5m

    You do the same with breadth ad draught. Program than calulates everything it can for each ''project ship'' given different statistical data and persumptions. Final goal is to find economicaly justified main dimensions.

    Of course I want to exclude as many projets as i can using different criteria. So the question arises: Is there any simple stability criteria other than GMmin? I found the GMmax criteria using formula in upper post, but... It doesn't seem to work right.

    Thank You for Your reply and link. I'll read it and ask questions later, if I have any!

    Best reguards!

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