Calculating Transver BM of a catamaran

Discussion in 'Stability' started by Grimorum, Mar 15, 2016.

  1. Grimorum
    Joined: Mar 2016
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    Location: MALAYSIA

    Grimorum Junior Member

    Hi All,

    I am a beginner in studying naval arch.

    Encountered a problem as follow and I cant seem to solve it.

    Each of the two hulls of a catamaran has the following dimensions

    Ord. No. 1 2 3 4 5 5.5 6
    1/2 Ord(CM) 0 4 6.2 7.2 6.4 4.9 0

    Length of each hull = 18m
    Displacement each hull = 5.3meter cube
    Ordinates are spaced evenly.

    the hull center lines are 6m apart.

    What is the transver BM of the boat?

    I convert all dimensions to meter, then using Simpson first rule to calculate the y cube. Then using the formula: (1/3)integrate y cube dx and with the excel sheet, using this transverse second moment of area and divide it by the volume of displacement.

    The answer I get is very far from the answer of 3.12m.

    Hope someone can enlighten me in this question and best would be list out your steps.
     
  2. RAraujo
    Joined: Apr 2010
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    RAraujo Senior Member - Naval Architect

    Are you taking into consideration that you have 2 hulls and also the added transfer second moment of area due to the fact that each hull is 3m apart from CL?
     
  3. Grimorum
    Joined: Mar 2016
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    Location: MALAYSIA

    Grimorum Junior Member

    RAraujo, very much appreciated, you just rang a bell in my head with that transfer second moment of area with the parallel axis theorem. totally forgotten about that. Got the answer now.
     
  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    If BM means "Bending Moment", you should get a result in kg.m.
     
  5. Grimorum
    Joined: Mar 2016
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    Grimorum Junior Member

    BM in my case is the Center of buoyancy to the metacenter.
     

  6. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Oops, sorry for my stupid mistake. I should have read your post more carefully.
     
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