Inclining Experiment: a more simple way

Discussion in 'Stability' started by quequen, Jul 17, 2011.

  1. quequen
    Joined: Jul 2009
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    Location: argentina

    quequen Senior Member

    I was searching for a simplest way to do an Inclining Experiment on small vessels and (roughly?) determining KG. I came to this simple deduction, and wish to know if this is right. If right, this can be easily inverted to get Heeling Angle for a given excentric weight, having KM, KG, and Disp. as data (I suspect it's not correct as it's too simple and I couldn't find something similar on many stability books). Comments will be appreciated...
     

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  2. quequen
    Joined: Jul 2009
    Posts: 369
    Likes: 15, Points: 28, Legacy Rep: 199
    Location: argentina

    quequen Senior Member

    Attached is a little spreadsheet using formulas from previous post. I'll appreciate if someone could compare outputs with some Inclination Experiment taken on real life.
    I wonder if it's accurate-enough for small vessels like sailboats, kayaks etc.
    Again, comments will be appreciated... :D
    Thanks
     

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  3. Paul Kotzebue

    Paul Kotzebue Previous Member

    Assuming the weight will move parallel to the deck line, as opposed to the heeled waterline as you have shown, then GM = Weight * Distance / Displ / tan (angle).
     
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  4. quequen
    Joined: Jul 2009
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    Location: argentina

    quequen Senior Member

    Thanks Paul, your formula is what I've seen on stability books, I will add it to the spreadsheet. What I thought is than when a small boat return to equilibrium, weight's movement line is no longer parallel to waterline, assuming that load comes from center deck. Also, I guess where the center of load's moment should be located: just from where it comes, or the vertical line passing CB and CG?
    Your designs are cool, by the way ;)
     
  5. Paul Kotzebue

    Paul Kotzebue Previous Member

    In an inclining experiment the heeling moment is always the weight multiplied by the distance moved. If I understand your question correctly, the answer is: just from where it comes.
     

  6. quequen
    Joined: Jul 2009
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    Location: argentina

    quequen Senior Member

    Attached is a spreadsheet having this simplified Inclining Experiment.
    And two images showing two different metods that produce exactly the same results. One of them uses tg(heeling) and G moves to G' over a line parallel to deck (the standard formula). The other uses sin(heeling) and cos(heeling) to correct Weight moment. In this second case, G moves to G' over a line wich is perpendicular to B'M.

    In reality, G moves to his new position G' over the stright line GW, wich is not parallel to deck nor perpendicular to B'M. I wonder if this produces a significant error :?:
     

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