damage

Discussion in 'Stability' started by jollyricard, Dec 27, 2010.

  1. jollyricard
    Joined: Jul 2009
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    jollyricard Junior Member

    ok, now my problem is:
    How do I determine the position of center of gravity of the three conditions
    test prescribed by the SOLAS?
     
  2. nettersheim
    Joined: Sep 2010
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    Location: France

    nettersheim Consultant

    You are free to choose position of center of gravity (KG) as you like provided in the end you get the Holly Graal :

    A (attained index) > R (required index)

    Obviously it should make sense with intact stability figures and you will have to determine final GM enveloppe curve coping with intact and damage criterias.

    It is a long way to Holly Graal ;)

    Fran├žois-Xavier Nettersheim
     
  3. ontwerp
    Joined: Sep 2009
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    Location: Netherlands

    ontwerp Naval Architect

    How to define initial case GM or KG's

    Some ideas are:

    1. Put your design or intact stability book load cases in a graph of draught vs. gm for each load case.
    2. Draw an envelope curve between the draughts of the initial conditions (with the line being above all the GM's.)
    3. If some of your loadcases don't fit the line and they are not critical, then change them.
    4. Consider if you want your ship to function mostly at one draught or at a range of draughts when you draw your line (make the curve slope to the point where you want to maximize your capacity, or make a valley where you want the range).
    5. Make sure you have enough ballast capacity to achieve your DL GM!

    It is not too strange to have your DL GM 4x as high as your DS condition.
    Depending on your type of ship you could start with DL at 2.5m, DP at 0.65m and DS at 0.60m for your GM values if you have no load cases besides your lightest seagoing (which you need to calculate your draught and trim for your initial conditions). Then after starting with those values you can easily optimize (increase or lower GM values - keeping load cases in mind) until you have an A>R. (Assuming you use a damage stability software like NAPA or Delftship which allows for quick easy optimization.)
     
  4. jollyricard
    Joined: Jul 2009
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    jollyricard Junior Member

    ok, many thanks
    but
    I do not understand the following problem:
    for my ship : loading conditions (dp, dl, ds) are already established as
    solas 2009 or not?
    must I verify only these conditions?
    must I to fix the center of gravity of these conditions?
    must I to fix trim for these conditions ?
     
  5. ontwerp
    Joined: Sep 2009
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    Location: Netherlands

    ontwerp Naval Architect

    ds - subdivision draught or design draught, this is decided by you or the result of the maximum summer draught from freeboard calculation
    dl - lightest seagoing draught (including trim from load case) normally ballast arrival condition - you make this loadcase depending on your minimum draught forward from your slamming calculation for your foreship construction, or depending on damage stability (it can be a feedback loop, if your ship is not meeting index raise the GM, but then you have to add ballast to loadcase to meet minimum GM from damage stability, but then you have to change DL in damage calculation)
    dp - related to dl and ds, according to solas 2009 rules

    You must fix GM for these conditions. The GM values you choose will become your damage stability minimum GM criteria.

    Trim of DL condition must match loadcase lightest seagoing condition, trim of other conditions is defined by you. Read the explanatory notes for more information about how to choose your trim range.

    Does that help?
     
  6. jollyricard
    Joined: Jul 2009
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    jollyricard Junior Member

    yes, thank you;
    now I think I have solved my problem
     
  7. chandru447

    chandru447 Previous Member

    If you are looking for prob stability, i hav a material to describe this prob stab.

    send me an mail chandru447@gmail.com
     

  8. smp
    Joined: Jun 2012
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    Location: Greece

    smp Junior Member

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