Seakeeping Standards

Discussion in 'Class Societies' started by abAndad, Aug 19, 2013.

  1. abAndad
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    abAndad Energetic Naval Architect

    Hi everybody,
    Does any have any Standard for Seakeeping of Semi-Displacement Ships and High-Speed Crafts?
    I find few formulas in DOD Standard, but it is not sufficient; How about ABS, GL,LR,...:?:
     
  2. Murat124
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    Murat124 Junior Member

    acceleration in X,Y,Z directions as the multiplier of g ( 9.8 m/s^2), wave period and wave height and probability ( for wave model (s) as the response of the vessel
    these are criterias for using in preliminary design. They are used for indicating criterias stability divisioning and for strength of the hull there are some softwares on the market which can calculate this values for a vessel
     
  3. timj68
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    timj68 New Member

    Great information. Thank you.
     
  4. gonzo
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    gonzo Senior Member

    European standards have limits on acceleration and frequencies.
     
  5. TANSL
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    TANSL Senior Member

    That's news to me. Could you explain it in more depth, Gonzo? What standards do you mean ?.
    Thank you
     
  6. Murat124
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    Murat124 Junior Member

    For the passenger crafts, comfort as it is essential ??
     
  7. TANSL
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    TANSL Senior Member

    It is not just comfort. The cargo transported by a ship, for example containers, may be subjected to accelerations in the order of 3 to 4 g's that the structure must withstand.
     
  8. Murat124
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    Murat124 Junior Member

    Then you should secure your containers better :) Your argument poins out container stacking- stowage design. it does not directly related seakeeping of the hull and does not changes any thing other than inner space dimensions of the holds
     
  9. TANSL
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    TANSL Senior Member

    Murat124, thank you for your kind advice: better make sure my containers.
    Can you explain what you were talking about in your post # 2 ?. I think I'm saying something like that.
    Seakeeping, maneuverability, stability, ... are behaviors that are strongly influenced by the possibility of bad fixed weights. I do not know if the comfort has a lot to do with the seakeepping.
     
  10. Murat124
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    Murat124 Junior Member

    Pascat Landing Craft

    if anybody who is related with Hover Craft or air cushioned vessel can give me explanation information about pascat technology used equipments for making air cushion
     
  11. gonzo
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    gonzo Senior Member

  12. TANSL
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    TANSL Senior Member

    Thanks Gonzo, nice article. I'm not sure what you want me to underline in it.
     
  13. Murat124
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    Murat124 Junior Member

    English Reading Skills :)
     
  14. BMcF
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    BMcF Senior Member

    "Seakeeping" covers a pretty broad area of topics.


    We refer often to STANAG 4154 for seakeeping objectives, particularly for naval vessels.

    ISO 2631 provides very useful guidelines and "limits" for human exposure to acceleration as it affects or promotes fatigue and/or the incidence of sea sickness.

    DnV put out a fairly detailed set of parameters in their "Comfort Class" initiative, some years back. I'm not sure it that is still available.

    In more recent years, with the various studies of coxswain injuries incurred on smaller fast military vessels, updated and/or new shock and vibration limits are being imposed.

    So, what reference you turn to depends very much on what facet(s) of the broad area called "seakeeping" that you are focused on.
     

  15. cmckesson
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    cmckesson Naval Architect

    4154 vs MII/MSI

    Hello Bill. Just a note that STANAG 4154 is excellent regarding methodology, but the limits proposed in the appendix are actually relevant only to monohull craft. They were derived by back-analysis of reported seakindliness of US combatants, I think the work was done by Ed Comstock. They do include some assumptions about periods that are only actually true with monohulls. (There is a buried assumption that the pitch period is about 3x longer than the roll period...)

    I go into greater length on this in my book. But the point here is that I respect the methodology, but suggest one be open minded about the selected criteria. MII and MSI may be better criteria for an unconventional hull.

    Also, somebody asked about PASCAT. What in particular would you like to know? There are several members who know a lot about the subject...
     
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