Inclining Test Using Double Bottom Tanks

Discussion in 'Stability' started by naserrishehri, Jul 28, 2013.

  1. naserrishehri
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    naserrishehri Senior Member

    DEAR FRIENDS
    Is it possible to use double bottom tanks as per attached file for inclining test ?
     

    Attached Files:

  2. gonzo
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    gonzo Senior Member

    What are you specifically testing for? I assume you are looking at increasing displacement by filling water tanks in the bottom.
     
  3. naserrishehri
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    naserrishehri Senior Member

    I'm going to use double bottom tanks for inclining test .
     
  4. gonzo
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    gonzo Senior Member

    OK, but what is the reason for the double bottom tanks? The drawing shows a double bottom that is flooded with water.
     
  5. athvas
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    athvas Senior Member

    Do u want to use the double bottom tanks as inclining weights?
     
  6. naserrishehri
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    naserrishehri Senior Member

    yes. i want to use ballast water as inclining weights .
     
  7. jehardiman
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    jehardiman Senior Member

    NO!

    That is a good way to to have another COUGAR ACE!

    Not only to you not know the exact weight and centers, you introduce free surface in the middle of the experiment.
     
  8. TANSL
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    TANSL Senior Member

    Although I do not like the idea, I am unable to say why I do not like it.
    Of course, you must absolutely avoid free surfaces. To find the added weight and center of gravity enough to have tanks sounding tables. I do not think that's a problem.
     
  9. jehardiman
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    jehardiman Senior Member

    Have you have actually metered a tank? It is not as clear cut as you seem to think and capacity curves can be off by tons. And that is just from temperture-density issues. The necessary accuracy needed for a proper inclining will never be achieved by using the ships own tanks.
     
  10. ldigas
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    ldigas Senior Member

    Temperature does not affect mass. It affects density and volume as a result of that, but mass stays the same.

    And although not the most precise solution, water ballast is used in inclining tests where solid weights are deemed inpracticable. However, some precautions are to be taken to ensure the test is properly conducted.
    Talking about large commercial vessels here.

    Something on that
    http://www.veristar.com/bvrules/B_3_a1_1_1.htm
    (ch. 1.1.2 I believe)
     
  11. TANSL
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    TANSL Senior Member

    jehardiman, the first thing I said was that I do not like the idea but you will have to give me some reason to convince me that it can not be done this way.
    I do not know if you know that in order to properly achive an inclining test, among other things, water density should be measured at a depth equal to half the draft of the boat. I do not know if we have a hydrometer, why can not we use it with the liquid in tanks.
    The volume of tanks, in any boat, is well known. The errors due to temperature may occur (what are these errors?) will not be greater than those produced with the total volume of the ship.
    So, I'm hoping that you show us reasons not to carry out the test this way, but for now, I do not see them. I'm not saying do not exist, but you should try a bit harder.
    Cheers.

    PS : One reason I can think that it is not feasible to use the double bottom tanks is because the heeling moment produced by them is not enough to heel the boat 2 or 3 degrees as required.
     
    Last edited: Mar 5, 2014
  12. TANSL
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    TANSL Senior Member

    I think I've found a reason to not do the test with the double bottom tanks: it is impossible to determine the zero point for measuring the deviation of the pendulum.
    What do you think?
     
  13. naserrishehri
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    naserrishehri Senior Member

    why impossible?
     
  14. TANSL
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    TANSL Senior Member

    I do not see how to do it without changing the displacement of the boat at some point. How you thought you get it?. Tell me about your procedure, please. DonĀ“t forget free surfaces.
     

  15. naserrishehri
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    naserrishehri Senior Member

    each level of water in double bottom considered as inclining weights .
    free surface effect shall be calculated by software and considered in
    calculations .
     

    Attached Files:

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