Stability Problems

DELFTship forum Hydrostatics and stability Stability Problems

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    • #38154
      Luiz Fuchs
      Participant

      Hello,

      I’m facing a problem with the stability of my “system” (see the picture)

      The “system” is composed by two retangular vessels (10x20x3m) that are carrying a metallic structure (60×7.5×7.5m). They will be used to transport the structure to the construction point.

      I assumed there’s no relevant pitch movement and the main problem is the roll movement.

      Assuming the software gives the righting arm based on the roll movement, why when I increased the transversal length (from 20 to 30 m) the stability presents worse results and when I decreased the transversal length (from 20 to 10 m) presents better results (bigger righting arm)?

      Attachments:
    • #38155
      Maarten
      Keymaster

      Hi,
      Can you share your model so we can have a look?
      thanks

    • #38158
      Jesus Cruz
      Participant

      It doesn´t make much sense what you are saying?, can you share an image showing the coordinates system?

      If you share the file I will run some calculations, and give you my thougths about it

      Regards

    • #38202
      Luiz Fuchs
      Participant

      Sorry for the delay,

      Here is the File.

    • #38204
      Jesus Cruz
      Participant

      Can you send it in 6.35 versión please, I can´t open newer versions….

      Thanks

    • #38205
      Luiz Fuchs
      Participant

      Hello!

      I can’t save in an older version, i don’t have access to the pro version anymore. :dry:

      thanks for the support!

    • #38206
      Jesus Cruz
      Participant

      Send me the drawing and data to cruzmayora@hotmail.com so I can reproduce your file in my 6.35 versión software and check the problema.

      Regards

    • #38214
      Sharat Jami
      Participant

      Hello Ifuchs,

      I hope this shall give you an idea about how the righting arm curve of a beamy hull and an narrow hull looks like
      Slide12.gif

      you can also see the comparision for different kind of hullforms
      ConstWidthPlus.gif

      So in your case the hull is pontoon, i.e it has high initial stability, but it shall last for only upto 10 – 15 deg, after that there is a consistent, decrease in GZ value and it vanishes around 40-45 deg i.e you, so these kind of vessels will be best suited for coastal water operations.

      the more wider you make the more stiff the vessel will become. so your max GZ value will increase at same lesser angle
      ,
      I have simulated your case kindly refer the GZ curve comparisions i have found.
      CASE-1: Width 30 m
      Screenshotfrom2016-03-2601-22-59.png

      CASE-2: Width 20 m
      Screenshotfrom2016-03-2601-24-27.png

      CASE-3: Width 10 m
      Screenshotfrom2016-03-2601-27-18.png

      I hope i must have clarified.

    • #38226
      Luiz Fuchs
      Participant

      mail sent.

    • #38229
      Luiz Fuchs
      Participant

      “jsharatchand” thank you for helping with your great report on this forum
      and
      “cruzmayora” for helping by e-mail (really, it helped a lot) :laugh:

      thank you guys!!1 😛

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