Calculations stability

DELFTship forum Hydrostatics and stability Calculations stability

Viewing 5 reply threads
  • Author
    Posts
    • #38309
      AvatarTran Van Cua
      Participant

      Hello Everybody, I have a Ship with length = 21.0 meters, Beam = 5.9 metes, Height = 3.0 meters. Almost of all is normal, but when I calculations stability for it, Heel angle only is 0, 10, 20, it not larger.
      Example: Displacement = 120, Hell angle is 0, 10, 20, it not larger.
      Displacement = 60, Hell angle is 0, 10, 20, 30, 40, it not larger.
      Displacement = 10, Hell angle is 0, 10, 20…..80, 90.
      I don’t Know about this.
      Is there anybody who can help???
      Thanks in advance,
      CuaNTU

      Attachments:
    • #38319
      AvatarRobert Holme
      Participant

      GM of 1.727m? are you sure this is not KM?

      IIRC GM should vary with displacement and where in a vertical plane the weight is added or subtracted.

      HTH

      Regards
      Bob

    • #38320
      AvatarTran Van Cua
      Participant

      I mean, Heeling angle only full 0 – 90 when I calculator with Displacement is very small compare to Ship. if I calculator with right Displacement is heeling angle only 0 – 20.

    • #38321
      AvatarTran Van Cua
      Participant

      Please help me!

    • #38336
      AvatarSharat Jami
      Participant

      I think its a classic mix up which everybody experiences for the first time when they execute stability on any software.

      The major idea of stability depends on buoyant hull which is considered, if there are any openings on the hull, the stablity GZ curve stops at that particular angle where the point gets immersed.

      I am showing a case study for better explanation which was executed in Freeship GPL software. which is primitive version of Delftship.

      A Box of dimensions L=21 m,B=5.9 m,D=1.5 m is submerged for a draft T = 0.5 which corresponds to Disp = 63.499 T,
      stability is assessed for 2 cases. for constant draft/disp.

      Case-1: Deck Surface closed.
      DeckClosed.png
      GZ curve comes as follows:
      GZDeckClosed.png

      Case-2: Deck Surface Open
      DeckOpen.png
      GZ curve comes as follows: you can actually see a sudden collapse in GZ, that is because at that angle the water starts flooding inside thus changing the displacement, hence here a much advanced concept of dynamic stability including ingress of water is applied to predict stability.
      GZDeckOpen.png

      Normally when performing intact stability check the body which is floating needs to be completely enclosed, a complete enclosure can be checked by an option called check model in delft ship. if leak points are observed your hull is open to flooding.

      I hope i have solved the issue.

    • #38337
      AvatarTim Stewart
      Participant

      Thank you jsharatchand, for taking the time to explain this.

      Regards Tim

Viewing 5 reply threads
  • You must be logged in to reply to this topic.