Any approved Naval Architecture software?

Discussion in 'Stability' started by Guillermo, Apr 26, 2008.

  1. Guillermo
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    Guillermo Ingeniero Naval

    I have already asked this question in some other threads of these forums, but I've got only a few answers and none of them from software developers.

    Is there, in the whole wide world, any Naval Architecture software (and I'm meaning stability ones, basically) officially approved by any governamental body, classification society, notified body or any other standardizing organization? In its case: what kind of approval?

    I have been told there are none in the USA and the UK (SNAME and RINA letters to our Association). Any other country?

    Cheers.
     
  2. Bijit Sarkar
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    Bijit Sarkar Naval Architect

    To my knowledge, there is no naval architecture software with such approvals, if by NAS you mean developing the design from the basic concepts. That would be like a govt. promoting a particular software company.
    However, softwares are there , TRIBON, MAXSURF, NAPA, SHIP CONSTRUCTOR, CADIA, and maybe more that are being used by govt. agencies, navies, and govt shipyards all the world over.
    Most classification soceities , however, have softwares for scantling and computational needs. LRPASS, DNV-Nautilus, IRS are but some of them that I know of.
    Most govt regulatory bodies accept their output.
     
  3. Guillermo
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    Guillermo Ingeniero Naval

    That's not the point.

    Problem is when you get diverging results for the same hull and CoG when you use different softwares. I have run up to four well known software programs for several boats and I got surprisingly diverging results in most of the cases.

    Governmental bodies ask to approve the Stability Booklets previously to the entry into service of commercial vessels, among them fishing ones. Many times this kind of boats comply 'in the border' with some of the IMO stability criteria at certain load conditions. In these situations the vessel may comply with one software and do not comply with other. Not complying can have a disastrous effect on the economies of a boatowner and his crew, if the boat is not allowed to go to sea till very expensive correcting works are carried on the boat, just because a given software is saying it doesn't comply with one criterium. But what if you run the stability with another software and the boat complies? Or the contrary, what if you think the boat complies but it doesn't? Which one do you trust? Which one the authorities trust? How we dare not to be sure about what we are doing? I have asked the Spanish authorities in written several months ago about how to proceed, after sending them a full study on a seagoing tug, run with all four software programs, and I'm still waiting for the answer. And as far as I know I'm going to be waiting all eternity. And the problem seems to be quite the same the world around.

    Has anybody experienced a similar problem?

    Cheers.
     
    Last edited: Apr 30, 2008
  4. Guest625101138

    Guest625101138 Previous Member

    Guillermo

    You should not be relying on governments to make the case for you. This is something they happily avoid. Also they are unlikely to endorse a particular product. I have seen some codes that are regulated written around specific equipment, although not named, but not software.

    You need to have confidence in the tools you are using. It is really up to you to test their accuracy.

    Why not test each of the software you have on something that can be easily calculated such as a cylinder, box and trianglular section. You can add complexity by combining simple sections. Tabulate the results and post a comparison - a "road test" comparison of stability software. I am sure there will be some interested followers.

    Rick W.
     
  5. Guillermo
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    Guillermo Ingeniero Naval

    Not some codes, but hundreds of codes on equipment, not to talk about the variety of codes on stability. Why not on stability software? Why it hasn't to be tested against a known database of known types of boats, to be approved prior to commercial use, i.e.? I have put this question to some relevant professional organizations and got two not excluding answers: a) it's not an easy task. b) authorities do not want to take on them the liability in case something goes wrong.

    And it can be there a third reason: software developers are not interested at all in this approval process happening.

    I propose something perhaps more interesting (simple forms may not be adequate for a comparison): choosing a real case of an existing fishing boat (no name, etc) and providing these forums' members with the hull in DXF format as well as a DWG general layout, lightship's CoG position, flooding point, table of capacities of tanks and solid loads' CoGs and weights for the four basic IMO criteria. Then interested members can run the thing by themselves and compare results afterwards.

    I'm not yet sure about the legal implications of publicly informing of what the name of the software used, as well as posting info on a particular and perhaps identifiable boat . Maybe a solution could be privately working only with a group of interested members. What do you think? Volunteers?

    Cheers.
     
  6. Guest625101138

    Guest625101138 Previous Member

    Start with the simplest test to see if they pass this one then work up in complexity. It is likely that the complexity of tankage will be where the good and also rans separate.

    The only stability software I have is Freeship. I have purchased Delftship but its stability component is an extra. Freeship and Michlet give identical initial stability.

    I can give Freeship a go for a complex hull but tankage would create complexity beyond it.

    I have seen people confused with units. For example some software gives RM in kgm whereas others give Nm. The factor of 10 difference is usually something that you pick up on but it does still cause confusion.

    Rick W.
     
  7. Guest625101138

    Guest625101138 Previous Member

    Naming the software used with the results is a public service. Only issue would be with the hull specifics if it is identifiable without the owner's permission.

    My preference would be a public thread with a concocted hull having the required complexity. However it is still worth knowing if the software types are doing the basics correctly. Sometimes errors can creep in due to the resolution used. So even the same software with different settings could give different results.

    Rick W.
     
  8. PI Design
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    PI Design Senior Member

    Hi Guillermo,

    I'm not sure if this exactly fits the bill, but the UK Ministry of Defence developed the GODDESS software (in the 70s/80s) for their stability calcs. In the late 90's GODDESS was replaced by Paramarine - which is commercially available through GRC (part of QinetiQ - formerly the Defence Evaluation & Research Agency). So, in summary, Paramarine is essentially a UK MoD derived stability software that is commercially available. I assume therefore it is offically approved by the MoD.
     
  9. MikeJohns
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    MikeJohns Senior Member

    Sounds interesting, I'd like to see the differing outputs so I know exactly what you are referring to.

    If you send me the hull and data I’ll give you the righting moments, flooding angles from my software.

    I’ve always run hulls through two packages and so far have never had any disagreement.

    cheers
     
  10. Guest625101138

    Guest625101138 Previous Member

    I will volunteer a hull for analysis.

    Not your typical hull but one that I am very interested in the stability.

    The LOA is 12.3m. Design displacement is 1.1 tonne. KG = 0.65m.

    Tankage is negligible.

    Rick W.
     

    Attached Files:

  11. joz
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    joz Senior Member

    Have you tried to so a search on the net on what yacht designers and naval architects use from their websites. You will find that some design firms list what programs that they use in order to design your boat. That you be a good start in seeking your the type of software that you will need to use.
     
  12. water addict
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    water addict Naval Architect

    for stability, the standard in the us govt is shcp. It was originally written by the govt. There are different versions floating around.
     
  13. gadfly
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    gadfly Junior Member

    In my opinion, ship stability calculation is simple.
    If th results calculated by different softwares are different, it shoud be the difference of their HYDROSTATIC CURVES.
     
  14. Guillermo
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    Guillermo Ingeniero Naval

    Thanks everybody for your contributions.

    I will send Mike and Rick (as well as any other interested) the files on a particular fishing vessel for you to run and then we'll share results (But Rick, I don't know if Freeship has enough capability. Not specially complicated tanks, but there are at least 12 of them)

    Water addict and PI design: those two softwares seem to be powerful tools. I didn't know them, thanks. They say they are considered 'industry standards' but it seems to me that's more a consuetudinary standardization than a formal one. All well known stab softwares have an implicit approval by their results being accepted in everyday's life, but that's not a formal and public approval (I know authorities use to test new softwares's results before admitting them for official stab calculations, but they do not 'stamp' the product explicitly approving it)

    Gadfly: Most programs produce very similar hydros, that's not the problem. Problems I've found are subtle and random differences in the KN curves as well as different KG positions derived from the same stability test.

    Cheers.
     

  15. Guillermo
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    Guillermo Ingeniero Naval

    Insisting on my post #3:
    not getting 25º for the maximum GZ, can become a disaster for a FV owner and crew. If this angle is 24º+ instead of 25º just for one of the IMO load conditions, authorities may stop the boat and ask for corrections to be carried on. This may bring, i.e., the necessity of putting the boat ashore, inmovilize it for several days or weeks, adding extraordinarily high ballast weights at the keel to gain those tenths of a degree, run a new stability test and calculations, and then submit these to be approved. A lot of money to be spent and a lot of days without going fishing. I've seen this happening several times. And this is for the simplest cases.

    But, what if using another software the angle is 25º (or higher) for all conditions and the problem could be avoided?

    Cheers.
     
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