Damage stability of fishing vessel

Discussion in 'Stability' started by Adarsh Edakkote, Apr 2, 2019.

  1. TANSL
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    TANSL Senior Member

    For a boat of 8.23 m, the curve of floodable lengths you got is very good, according to how I interpret it.
     
  2. RAraujo
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    RAraujo Senior Member - Naval Architect

    upload_2019-4-8_8-8-6.png


    The only reference to stability I could find, in the referred Rules, are as per above and no reference to floodable length...
     
  3. Adarsh Edakkote
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    Adarsh Edakkote Junior Member

    See below point number "k"(This is as per KIV 2015 amendments)
    upload_2019-4-8_17-13-11.png
     
  4. Adarsh Edakkote
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    Adarsh Edakkote Junior Member

    Ya.My calculation was correct .The flooding calculation is approved.
     
  5. TANSL
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    TANSL Senior Member

  6. RAraujo
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    RAraujo Senior Member - Naval Architect

    Good you sorted it out!

    I note the 2015 amendments but just asking for flooding calculations without mentioning any other additional information (type and dimension of damage for example) or criteria for compliance is not enough...
     
  7. TANSL
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    TANSL Senior Member

    The concept of floodable length has little to do with the length of the damage. In the calculation of floodable lengths the dimensions of the damage do not intervene at all. Nor are there any more criteria to fulfill than not sinking the margin line. Nothing else is needed.
     
  8. RAraujo
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    RAraujo Senior Member - Naval Architect

    TANSL
    1. Flooding calculations, as mentioned in the amendments, might not be related to floodable lengths (could be the equilibrium and stability conditions of the vessel after the flooding of any main compartment for example);
    2. There is no reference to margin line in the same amendments;
    3. For floodable lengths calculation a minimum GM may also be considered.
     
  9. Adarsh Edakkote
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    Adarsh Edakkote Junior Member

    Yes correct
     
  10. TANSL
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    TANSL Senior Member

    The correct phrase is not "might not be related ...", but "it is NOT related ...".
    If you start doing this calculation on a ship, you can check that you do not need to know the damage's size at all, but if you do not know the position of the margin line, you can not calculate correctly. Do not give me the reason without more, please, just try to do the calculation. Then, if you keep thinking that I am wrong, explain why and I will gladly admit it, without any problem.
     
  11. RAraujo
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    RAraujo Senior Member - Naval Architect

    TANSL,
    I think you are missing the point - just saying that flooding calculations are required is not enough.
    It makes no reference to what type of calculations are required (they do not mention floodable lengths nor margin line at all) and for some type of flooding calculations, like, for instance, those on deterministic damage stability, the size and location of the damage are required. Thus the word "might"...
    And yes, I've done plenty of floodable length and damage stability calculations... And I've drafted a number of regulations myself so I know when one is not properly written.
     
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  12. TANSL
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    TANSL Senior Member

    RAraujo, OK, I think I've already clearly said everything I had to say.
    You have my respect, even if we do not agree.
     
  13. Umair
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    Umair Junior Member

    Hello sir,
    I am doing naval architecture, as a project I am working on a tool to calculate damage stability by using programming code. But I have issues in manual calculation for that reason I can't move to the code.

    I have already written a code to calculate KN CURVES which is 95%+ accurate to the available commercial softwares. Now I want a help to calculate damage stability just floodable lenght curve. I am facing some issues like selection of method (btw I have selected loss of buoyancy method) is it accurate?

    secondly how the iteration will work? Because in each iteration my draft values get increases and after 6-8 iteration ship actually sinks
    Can you please share some manual calculation if you have any study related material?

    Thanks
     
  14. RAraujo
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    RAraujo Senior Member - Naval Architect

    Have a look at Principles of Naval Architecture, Vol. I, Chapter III, Section 4... There is a lengthy explanation on how to do it manually (no KN curves required for floodable length calculation though)..
     

  15. TANSL
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    TANSL Senior Member

    Iterations should include increases and decreases in draft as well as positive and negative trim of the boat. A lower average draft (that is, the draft in Lpp / 2) can mean a greater displacement when changing the trim. Keep that in mind for your calculation procedure.
    I don't think anyone can offer you a sample of a handmade calculation simply because when there were no computers that calculation was not done.
     
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