Weather Criterion

Discussion in 'Stability' started by santoo, Nov 30, 2010.

  1. santoo
    Joined: Apr 2010
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    santoo Junior Member

    Dear All,

    Can anyone help me to solving my problem for pax ferry stability?
    In IMO Intact Stability Res. A.749(18) 3.2 Severe wind and rolling criterion (weather criterion) said that "Area 1" should be greater than "Area 2".
    In my case, Area1/Area2 49% (at LWL). I suspicious that freeboard and Air Draft are cause of fail, but i already try to modified draft level. And the result is just fail. I can't modified my hull and my layout arrangement.
    Can anyone help me? what can i do to solving this problem?
    I wait for replay.

    Thanks a lot..
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Santoo

    Well come to the real world of design. When your design/vessel does not meet certain criteria, you have to become creative to ensure the vessel passes. This is design!

    What is driving this failure??...you need to establish this. Usually in stability it is either hull form and/or KG. So, if you can't alter the hull form, alter the KG to suit.
     
  3. santoo
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    santoo Junior Member

    Ad Hoc, Thanks for your reply.

    I agree with you about hull form and/or KG. :):)
    I already try to change KG value in lowest position, but downflooding point at 29.2 deg of heel.
    I attach snap shot of may model, u can see the freeboard and downflooding point.

    So, what should i do next...? :(:(:(
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Nothing attached :(
     
  5. santoo
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    santoo Junior Member

    Upss... Sorry...


    [​IMG]
     
  6. Perm Stress
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    Perm Stress Senior Member

    Make your downfloding point ~50-60 degrees.
    Make hatches/doors watertight.
    Add some watertight deckhouse/superstructure/trunk.

    This should solve your problem.
     
  7. santoo
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    santoo Junior Member

    Perm Stress, thanks for your answer,

    About 1.5years i am work in stability calculation, especially for barge and tug boat. So this is my first experience to calculate passenger ferry (HSC).
    And opportunely i get a vessel with big enough of air draft and area.

    For make hatches/doors watertight as you said before, in my model a window is become a downflooding point. And a deck line become down to passenger room.
    You can see in my attachments.

    Thanks...
     

    Attached Files:

  8. santoo
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    santoo Junior Member

    Sorry,
    A wide window in main deck is downflooding point, isn't it?
     
  9. Perm Stress
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    Perm Stress Senior Member

    It depends.

    For damage stability it has to be WATERTIGHT in order to consider room as closed.

    For intact stability it has to be only WHEATHERTIGHT in oreder to consider room as closed.

    Many details also depend on regulations to be applied: Load Line Convention, Classification society rules, any local/special rules...
     
  10. Perm Stress
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    Perm Stress Senior Member

    OOPS!
    downflooding point is point, which, if submerged, make PROGRESSIVE FLOODING of otherwise closed compartments possible.
     
  11. santoo
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    santoo Junior Member

    Thanks a lot for your clear answer,

    About Load Line Convention, i don't have any reference for this one.
    Would you mind to explain to me about how to get freeboard value based on Load Line Convention?

    Thanks a lot for all your response, very helpful.
     
  12. Perm Stress
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    Perm Stress Senior Member

    It is not so easy to explain... :)

    It is a small book with lots of regulations. Search in library or go to IMO website and order it.

    However, if your ferry will sail inland waters of single country, Load Line Convention may be not applicable.
     
  13. santoo
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    santoo Junior Member

    Ok Perm...

    Thank you so much for your help...
    Hope i can be your good friend...
    Sorry, my english not so good...
     
  14. Perm Stress
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    Perm Stress Senior Member

    No problem.

    You welcome.
     

  15. santoo
    Joined: Apr 2010
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    santoo Junior Member

    Perm, my Ferry still become fail for weather criterion.
    U can see in my attachment, how about this?
    Freeboard area is so large, isn't it?
    What can i do? to make my ferry not fail in weather criterion.
    :confused::confused::confused:
     

    Attached Files:

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