Calculating KG

Discussion in 'Stability' started by ed198, Sep 24, 2018.

  1. TANSL
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    TANSL Senior Member

    ... so you can use the formula in post #4.
     
  2. ed198
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    ed198 Junior Member

    Ok thanks ...what does KC refer to pls?
     
  3. TANSL
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    TANSL Senior Member

  4. ed198
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    ed198 Junior Member

    Ah ok don't have that...
     
  5. TANSL
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    TANSL Senior Member

    What is really what you have, inclining experience data, calculations, drawings, etc ... of your boat?
     
  6. ed198
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    ed198 Junior Member

    I have the drawings on Rhino however only trial version ...and as mentioned Gm calculation from the inclination experiment...
     
  7. TANSL
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    TANSL Senior Member

    To calculate the GM at a certain displacement and trim you need to have performed the calculations of the hydrostatic values. One of the values obtained in these calculations is the KC value. Do you have any calculation or how have you come to deduct the value of the GM?
     
  8. ed198
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    ed198 Junior Member

    If you can't help no problem...as far as i know you can calculate GM from the inclining experiment which i did
     
  9. TANSL
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    TANSL Senior Member

    Yes, I can and I want to help and that is what I am trying to do from post # 4 ..
    Trying, no doubt about it, to help, I'll tell you that if you already have the GM, you just need to calculate the Rmt and the KC (see formula in post # 4). To obtain these two values it is enough that you look at the hydrostatic values (which I suppose you have already calculated).
    It would be of great help, for someone to help you, to tell us how you have made the experience of stability and the data you have obtained from it: draught at fore and after perpendiculars, length of the pendulum, average angle of heel, weights transferred, distance of translation of the weights, main characteristics of the shipboat, body lines plan, hydrostatic values ....
     
  10. tlouth7
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    tlouth7 Junior Member

    It sounds like you have a 3D model of the boat? In that case you could find the centre of buoyancy in CAD. The easiest way is to create a solid of the underwater hull (check this has the same displacement as you found by weighing the boat). The centre of mass of this solid is the centre of buoyancy.

    You can then use TANSL's formula
     

  11. jehardiman
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    jehardiman Senior Member

    Tansl is correct, you can calculate GM without knowing KC (called KB here in the USA) or KG. You really need the curves of form to get KG from the GM. See the following post ( and ignore the snark)… Calculation of GM https://www.boatdesign.net/threads/calculation-of-gm.8852/#post-60405
     
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