Fishing Vesels stability

Discussion in 'Stability' started by Guillermo, Mar 8, 2008.

  1. Guillermo
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    Guillermo Ingeniero Naval

    Freeing ports are of upmost importance for the safety of a fishing vessel. AdHoc is right about the minum size they must have. I don't know how it is in other countries, but in Spain if a fishing vessel does not comply with the regulamentary freeing ports area, it is not allowed to go to sea.

    A problem often encountered is that crews do close such freeing ports, or severely limit their effective area by using multiple rods to form a grille, either to avoid sea water coming in through them or then to avoid fishes and/or ropes, etc, going out through them. Sometimes freeing ports are obstructed by on deck fishing gear, boxes, ropes, etc. This severely affects the ability of freeing ports to quickly evecuate water, putting the boat in danger of capsize. I know at least three fishing boats lost because of this reason, one of them causing five causalties and six another.

    Talking about limiting rules, we do not have the 65' limit in Spain, but other limitations. As I have told before in this thread, the EU is limiting the total GTs of each country's fishing fleet as a contributing rule to limit the fishing effort on the fish stocks. Spain is one of such countries.

    GTs are related to the underdeck and overdeck volumes of vessels. Rules allow an owner to build a new fishing boat if he/she scraps one or more old fishing boats totalling an underdeck volume equal to the underdeck volume of the desired new boat. Overdeck there is the possibility to increase volumes to allow for more comfortable quarters and better protection for crews.

    In my opinion this kind of ruling has proved to be perverse, as owners and designers force boats designs to the limits of the rules, producing sometimes dangerous units. If you are an owner and are limited by the underdeck volume of your old boat to build the new bigger one you want (longer and beamier) because you want to catch more fish (united to a bigger power of engines and fishing gear, of course), then you ask your designer to design such a boat. And what does the designer do? If he/she wants to keep you as a client, matching your desires of a longer and beamier boat, he/she has to 'play' with moulded depth and hull forms to match the available underdeck volume. In the limits this produces boats with a severely limited loading ability when stability criteria are to be matched (lack of enough freeboard)

    This designed low loading ability drastically limits fuel and fishing gear carrying ability as well as limiting captures to be carried. So designers and boatyards produce boats which only comply with stability criteria the day they pass the stability tests. In real life operation such boats are overloaded with fuel, gear and catches, severely affecting their stability.

    This is killing people in Spain. Unluckily we had to regret two more casualties in the last two weeks, because of two fishing boats capsizes, one of them in excellent weather.

    Fishing efforts have to be limited by the quotas asigned to fleets/boats, not GTs or size of the boats. Catches are the ones which should be tightly inspected both at sea and in ports, the way they are inspected in NAFO waters, etc, not the measurements of the boat. If a FV owner builds a boat too big or too small for his/her quota, that should be his/her enterpreneur's risk.

    Decreasing stocks (overfishing), low fish prices and always increasing operational costs are in the root of all this problems.

    Cheers.
     
    Last edited: Sep 23, 2009
  2. Guillermo
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    Guillermo Ingeniero Naval

    Hi all!
    Here you have the link to the web page where the papers and presentations at the seminar on Fishing Vessels' Crews and Stability have been uploaded:

    http://www.ingenierosnavales.com/wfe2009.asp

    There are two still missing, for different reasons, but I hope we'll be able to solve that soon.

    Cheers.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    The Deakin paper is, as always, excellent.
    The wave ht formulae was developed during the MCA research projects on HSC stability, for the next update of the HSC Code.
    http://www.mcga.gov.uk/c4mca/rp509_summary_report.pdf
    The results were remarkable and was felt at the time worthy of further investigation as it appeared to hold true for all ship types, nice to see it finally being used across the board.
     
  4. Guillermo
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    Guillermo Ingeniero Naval

    Yes, Barry's work is of great interest. I hope our maritime authorities use its reccomendations for our fleet of small FV.

    I also would like to bring this thread readers' attention to the fact that the system developed in Iceland has brought ZERO stability related accidents in the last six years. It can be done if both authorities and fishermen want to.

    Cheers.
     
  5. mallia.s
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    mallia.s Junior Member

    IMO book

    It seems that this topic has become quite hot!...

    Has anybody got 'Code of safety for fishermen and fishing vessels' published by the IMO, or at least appendix 6 of this book, as It has a test how to 'approximate a small boat stability by means of the rolling period test'

    Cheers!!

    Will greatly appreciate any help
     
  6. Guillermo
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    Guillermo Ingeniero Naval

    I do have the Code, but what you mention is in Part B, Annex III and its Appendix.
    How can I help you?
     
  7. mallia.s
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    mallia.s Junior Member

    Good evening!

    Well, actually I was browsing through the book on Google Books, so I can not really see everything. Even the table of contents is not always available.

    To put you in the picture, I am trying to evaluate a 22ft fishing boat hull in terms of stability as part of a thesis. I was looking through this book as to find some standard tests to evaluate/establish the basic stability criteria of the mentioned boat. At one time I managed to 'sneak-peak' one page of 'how to approximate a small boats stability by means of the rolling period test', which is on page 17* (I can not recall correctly), from the book: 'Code of safety for fishermen and fishing vessels' by the IMO. So this all boils down that I don't know exactly where this section lies in this publication, and have got no excess to it!

    If you could tell me how the rolling period test procedure is carried out, it would be greatly appreciated!

    Best regards

    Steve
     
  8. Guillermo
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    Guillermo Ingeniero Naval

  9. mallia.s
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    mallia.s Junior Member

    Thanks for the link, but the page that shows how to apply your data is not visible, unfortunately.

    Thanks
    Steve
     
  10. Guillermo
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    Guillermo Ingeniero Naval

  11. mallia.s
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    mallia.s Junior Member

    yes, it is a bit weird. I also tried to open the link using an other internet browser, but even a fewer pages were displayed!

    thanks for your help sir!


    good day

    regards

    steve
     
  12. mallia.s
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    mallia.s Junior Member

    Hi, just a small question, how do you apply the parameters to find 'F' in the GM equation. I am using the rolling periodic test from the web page: http://www.tc.gc.ca/marinesafety/tp/tp2534/appenix-to-appendix-iii.htm

    Here, it only sates: 'where F is ...(to be determined for each particular vessel by the Administration).'

    Is it related to the diagram related below? How is this to be translated?

    Can someone give an example with the metric version.

    Thanks for your help!!


    steve
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    The clue is given in
    2. The method depends upon the relationship between the metacentric height and the rolling period in terms of the extreme breadth of the vessel

    In other words, you must determine the natural roll period first, then use the nomogram to obtain the GM.
     
  14. Guillermo
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    Guillermo Ingeniero Naval

    Sorry for the delay in answering but I've been traveling.

    For a given vessel you shoud perform both a rolling period test and a full stability experience. From the first you have the period and from the second you can calculate the initial GM for the desired load condition for which "F" wants to be known (F varies with the loading of the vessel). Then you apply the simple formula F = GM * T^2

    If you do not have the possibility of doing a proper stab test (i.e. you do not know hull lines) then F is estimated from some known values. For displacement fishing vessels F uses to be taken as 0,8 as an approximation.

    Cheers.
     

  15. mallia.s
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    mallia.s Junior Member

    Hi again,
    The fishing vessel is a 22ft (6.7m) LOA and 2.5m Beam extream. After doing the rolling period test, the time for 1 oscillation came out to be T = 2.53s.
    I would now need to find the GM.
    What value should I consider f? (as B is known as well - 2.5m) using the formula GM = [(f.B)/T]^2, right?

    Thanks for your patience!

    Regards

    Steve
     
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