Maxsurf Modeler Tanks

Discussion in 'Stability' started by Mitch1990, May 14, 2020.

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  1. Mitch1990
    Joined: Feb 2020
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    Mitch1990 Junior Member

    I have taken to using floodable length analysis, it takes some pretty serious calculation to determine the attained subdivision index according to the code
     
  2. Mitch1990
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    Mitch1990 Junior Member

    I have run the flooded length analysis using the defect criteria in maxsurf which is a max trim angle of 10 and minimum GMT and GML of 0.2, is this something I should be able to find in the ABS?
     
  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Don't complicate your life, my friend. The study of floodable lengths has nothing to do with stability criteria. Perhaps it would be good if you gave a review of the theory of all these issues.
     
  4. Mitch1990
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    Mitch1990 Junior Member

    Sorry I was talking two conversation at once, I need to calculate the projected surface area for wind pressure in order to develop the limiting KG curve (this I know understand) and another component of the design is to determine the subdivision attainment index. It is the subdivision attainment index that has me a little stuck.
     
  5. TANSL
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    TANSL Senior Member

    As far as I know, the area exposed to the wind should not be necessary to calculate the curve of the KG limits, but I can be wrong. In any case, that area is easy to determine. Draw the longitudinal profile of the ship, including superstructure and everything on decks, and measure the area above the waterplane as well as its barycenter.
    As for the subdivision, I suppose you are trying to do the stability study after damage by the probabilistic method. If so, I am afraid I cannot help you, apart from recommending that you read what the IMO/SOLAS indicates in this regard and that you do not try to do the study by hand. Trust Maxsurf but knowing perfectly the data you must enter for each study.
     
  6. Mitch1990
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    Mitch1990 Junior Member

    What is the meaning of a convergence error in maxsurf?
     
  7. Mitch1990
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    Mitch1990 Junior Member

    For those interested, I simply restarted my model and now it works just fine... no failure to converge at all. Although I was getting results with pass/fail previously and now I am getting not analysed.
     
  8. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Have you sorted out your issues now?
     
  9. Mitch1990
    Joined: Feb 2020
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    Mitch1990 Junior Member

    For completeness, the original error when applying the IMO stability criteria for severe wind was based on a cross referenced calculation not being conducted. How do I stop this from happening in the future? it is seemingly random in that I can open and close maxsurf stability and the error will resolve itself.
     
  10. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Im not 100% sure what your asking - what do you mean by

    This is not clear
     
  11. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    There is nothing random in the calculations made by a software (unless it have been asked to generate a random number, and even then it only uses a procedure that is actually pseudo-random). Software does not think, and even less does it think each time in one way. Fortunately, the software does nothing but carry out, very quickly, what the programmer has asked it to do. So, the cause of that "randomness" you should look elsewhere.
    The user always has the tendency to think that the program is failing but what is more likely is that the fault comes from the user.
     
  12. Mitch1990
    Joined: Feb 2020
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    Mitch1990 Junior Member

    You're not wrong, maxsurf is quite difficult as software just to interface with. After going through all the criteria, I needed to conduct large angle hyrdrostatics before conducting the limiting KG analysis. I am not sure if this is required as I couldn't find it in the Maxsurf documentation, but it works. Is it to do with heeling lever calculations?
     
  13. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    When calculating the KG limits, the program heels the boat at various angles, at each displacement, until one of the stability criteria is not met. Although some applications do not, Maxsurf, when heeling the boat, also applies the trim that would actually occur.
    I don't know if this can clarify your doubts.
     

  14. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Are you talking about separate issues here?

    Are you not sure large angle stability is required,
    or
    Are you are not sure if limiting KG is available in maxsurf?
    or
    something else?
     
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