Stability Issues on my TUG - pls help!

Discussion in 'Stability' started by jfrech, Apr 3, 2014.

  1. jfrech
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    jfrech Junior Member

    Thank you for that pic, nice to see where the waterline level lies.
     
  2. Vinassman
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    Vinassman Junior Member

    I may be burned fir heresy if I say that but isn't there a quick and dirty way to estimate the stability of this tug? I mean if the OP is only interested to check the transverse stability, can't we just estimate the VCG with some good margins and if the results are fine then the matter is closed?

    If we take the geometrical center of gravity of the hull plus say 10%, won't we be able to get some conservative results?

    I'm just trying to help here :D, don't throw me in the fire :).
     
  3. TANSL
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    TANSL Senior Member

    Your attempts to help are very laudable, but we said something strong deserve it.
    Sufficient or insufficient stability may depend lives, so please do not take shortcuts.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    A quick audit of the weight of the additions since its previous incarnation should allay fears.
     
  5. TANSL
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    TANSL Senior Member

    Okay, but as long as the position of the C of G of the ship before the transformation is known.
    In any case, if the vessel is required to comply with any regulations, there are several occasions where it is mandatory to perform a new inclining test. I do not know them by heart so I'll list only a few of them:
    - The total weight has changed by a certain percentage (I forget which). Changes in number and distribution
    - Have changed the lines of the hull.
    - The engine has been changed
     
  6. DCockey
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    DCockey Senior Member

    As far as I'm aware no legal/regulatory stability requirements apply to pleasure boats the size of the jfrech's tug in the US and Canada. In the original post jfrech said "I intent do use vessel as a pleasure cruiser", not as a commercial vessel.

    For smaller vessels which are subject to stability regulations Transport Canada has developed a "simplified stability test" which does not need the vessel's lines or CG location. It involves testing the vessel with movable weights representing the weight of the maximum passenger and cargo capacity and is described at http://www.tc.gc.ca/eng/marinesafety/tp-tp14619-menu-1524.htm . Even though it is not required by Canadian regulations jfrech could test his boat with this method. The website notes that the method is more conservative for maximum load than the results from applying the ISO regulations and methodology. The USCG also has a similar simplified stability method which can be used by smaller vessels subject to stability requirements in place of the full inclining test and metacenter calculations methodology.
     
  7. TANSL
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    TANSL Senior Member

    The USCG, like many other governments of many other countries, have a method to assess the stability of vessels under XX GRT (can not remember the value of XX, around 30 GTR). This method is being abandoned by many administrations, being obsolete, to apply the method of ISO 12217, is but an experience of stability made ​​certain "recipes" that simplify, sorry, do not simplify the contrary, but tries as possible, roughly determine the position of the C of G without the need for hydrostatic calculations or definition of the cross curves of stability.
    I have no idea what the government of the United States of America or Canada are doing but it would be wise to ask them how they want action with that boat.
    Recreational craft, at least in Europe, have a very extensive regulation, which is not easy to fulfill.

    Correction: I have to correct myself. The simplified experince not try to find out the position of the C of G of the ship but simply check that under certain conditions (full load) ship high heel does not exceed a certain angle and also the deck is not immersed
     
    Last edited: Apr 12, 2014
  8. DCockey
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    DCockey Senior Member

    The US and Canadian simplified stability methods are alternatives to a full stability analysis. Generally a greater number of passengers/cargo can be approved if the full stability analysis is done. I know of an electric launch which was permitted the desired twelve passengers after the full stability analysis was done, but was only allowed six or so under by the simplified method.
     
  9. TANSL
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    TANSL Senior Member

    Everything that follows are my opinions. As I do not know the rules USA or Canada, I can not guarantee anything about what there is. What I can say is that there is no "alternative" methods that everyone can choose or reject. Each vessel must comply with to be met without alternatives.
    On the other hand I want to comment that the boat got to give him the classification of passenger vessel for 12 passengers was ill-advised. A merchant ship, with twelve passengers or less need not be classified as a passenger ship.
    And finally, to say that, in my oponión, regulations in all countries is always very similar, if not it's the same. If there were a country, more benevolent than others, all ships would ask the flag of that country
     
  10. Tad
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    Tad Boat Designer

    Once again....In Canada there is no stability requirement for existing private pleasure craft of this size and construction date. There are all kinds of standards which could be applied, but none are required. The vessel's safety in operation is left up to the owner, and what value he places on his life and that of his friends or family. Apparently in this case that is less than $1500.
     
  11. DCockey
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    DCockey Senior Member

    What boat are you referring to about 12 passengers? I don't recall seeing anything about the original poster wanting to carry 12 passengers.

    If it the electric launch which I mentioned above, it is a completely different boat than the OP's tug. I mentioned it because it is an example where the simplified stability method is very conservative compared to the full analysis. There was nothing ill-advised about it being rated for 12 passengers.
     
  12. TANSL
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    TANSL Senior Member

    Once again .... I do not know what happens in Canada, but from another point of view, I would be surprised if, for example, an insurance company would like to open a policy with a reasonable price for a boat that does not meet nothing and no one knows how or certify fleet conditions..
     
  13. TANSL
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    TANSL Senior Member

    Maybe I misunderstood this paragraph.
    Perhaps I have misunderstood "was permited" (not clasified). Sorry.
     
  14. DCockey
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    DCockey Senior Member

    That may be true for larger vessels used internationally. But it is not true for smaller vessels, and vessels used within a single country. Boats used in the US and Canada, unless short-term visitors, need to meet the applicable US or Canadian regulations only. And for some boats those rules are significantly different than rules in other countries; sometimes more strict, sometimes less strict.
     

  15. TANSL
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    TANSL Senior Member

    I do not doubt you're right. You know very well what you mean, I guess. I'm curious to know what these regulations to be met by small boats in USA or Canada. Any help?. Thanks.
     
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