ISO 12217-1 Calculation Swamped Stability and Buoyancy Test

Discussion in 'Stability' started by Arteaga27, Mar 21, 2024.

  1. Arteaga27
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    Arteaga27 New Member

    Hi, I would like to know if it is possible through calculations to validate Swamped Stability and Buoyancy indicated in Annex F.
    In the standard you can read the following: "The methods described in F.2, F.3 and F.4 shall be used, either by actual test or equivalent calculation. "

    I want to know about equivalent calculations.

    I haven't found anything in forums or books.

    I appreciate the answers, Thanks
     
  2. TANSL
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    TANSL Senior Member

    Of course, when one is carrying out the basic project of a boat that must comply with ISO standards, there is no other solution than to verify compliance through theoretical calculations. These calculations are no different than those required for any other ship that must comply with, for example, SOLAS. Nothing special, then, in the ISOs.
     
  3. Arteaga27
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    Arteaga27 New Member

    Please could you tell me where I can read about these equivalent theoretical calculations, because I understand that in these tests water should enter the boat and comply with stability and flotation. What I don't understand is how to calculate the amount of water that would enter. Thanks
     
  4. TANSL
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    TANSL Senior Member

    The swamp test, as I understand it, consists, with the boat in a certain load condition ( which we will call Swamp Test Load Condition STLC), in the following:

    - Real test:
    1.- with all hatches and watertight doors closed:
    2.- fill all floodable spaces with water as high as possible (that "highest" has to correspond, logically, to the lowest point of the bulwark or side because from that height the water overflows over the bulwark) .
    3.- check that the boat maintains a large part of the bulwark above the waterline. That is, the ship, once flooded, retained enough buoyancy to not sink completely)
    - Therefore to carry out the theoretical verification:
    1. The total volume of water that can be shipped is calculated up to a height that corresponds to the lowest point of the bulwark/side. (see attached picture)
    2.- calculate the weight of that volume of water and add it to the weight of the STLC.
    3.- With this total displacement, the draft to which it corresponds is interpolated into the hydrostatic values.
    4.- it is verified with that draft, that part of the bulwark is out of the water​

    The STLC load condition must be the light ship + plus the weights indicated in table F.5 of the standard, placed so that the trim of the boat is the design trim.
     

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    Last edited: Mar 21, 2024
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  5. silvestre
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    silvestre Junior Member

    The standard mentions the possibility of using "equivalent calculations" instead of actual tests for the methods described in sections F.2, F.3 and F.4. However, it does not provide details on what calculations would be considered equivalent. I have also not come across any specific calculation methods or formulas outlined in forums or reference books for this purpose. Perhaps reaching out to the technical committee that developed the standard or naval architecture experts could provide more clarity on acceptable equivalent computational approaches.
     

  6. TANSL
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    TANSL Senior Member

    Maybe I should have explained the test in more detail :
    The tests aim to demonstrate that there is adequate buoyancy and stability after the boat has been flooded. In one case it is assumed that the ship sinks horizontally, without heeling or trimming, and in the other it is assumed that the ship is first heeled by placing certain weights and then sunk.
    Therefore, it is a matter of, by adding weights, flooding the boat and then checking its conditions. To do this, the rule says that the boat should be tilted or submerged so that water enters until the level of the boat inside and outside coincides. So what you must calculate is the amount of water that can be put in each test and see if the indicated requirements are met.
    In case F3 you must assume that the boat has been tilted with weights previously placed under the conditions marked in figure F1. With this inclination, calculate the total amount of water you can ship. Once the amount of water loaded is known, the equilibrium flotation in the initial load condition is calculated, plus the weights used for the test, by moving these weights to the points marked in figure F.1.. Heel, now, should not exceed 45ยบ
    In test F.4, the boat must float with at least 2/3 of the gunwale out of the water.
     
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