Stability Issues on my TUG - pls help!

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

  1. DCockey
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    DCockey Senior Member

    In the US boats under 20' in length which are not sailboats, canoes, inflatables or multihulls, and which are intended to be used for recreation, have to meet a set of rules governing rated passenger capacity, motor power and floatation when swamped. Ike, a regular contributor here, has a website with a lot of information about the US rules. http://newboatbuilders.com/ The US Coast also has a website with the rules. http://www.uscgboating.org/regulations/boat_builders_handbook_and_regulations.aspx

    Information on Canadian rules for small boats is at http://www.tc.gc.ca/eng/marinesafety/debs-obs-construction-menu-2029.htm
     
  2. DCockey
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    DCockey Senior Member

  3. Tad
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    Tad Boat Designer

    In this country the only usual requirement for insurance is a a current survey, which does not mention stability (and few surveyors are qualified to assess) . In addition there is sometimes some requirement of owner/operator experience.
     
  4. TANSL
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    TANSL Senior Member

    Thanks DCockey for this enormous amount of information. I will provide of patience for review slowly.
    I have seen references to SOLAS and ISO standards, which makes me think that, as I said before, everyone says the same things.
    Thanks again.
     
  5. TANSL
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    TANSL Senior Member

    Sure you're right, I have no reason to doubt it. It just seems too risky for someone to secure a thing, without checking that this will not overturn or the amount of people it can carry safely.
     
  6. Rurudyne
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    Rurudyne Senior Member

    Indeed.

    Some time ago I came across an analysis of Spray by Andrade in the Rudder from a long time back, just a month after Spray was lost. ( http://babel.hathitrust.org/cgi/pt?id=mdp.39015022693553;skin=mobile#page/509/mode/1up )

    Aware that a particular NA had written about Spray himself I sent him an email with a link to the article just in case he thought he might enjoy reading it. He was kind enough to send me back a reply and one of the things he said was that the VCG apparently used for the article was wrong by maybe 8" ... which kinda got me thinking: Andrade had apparently published his own lines for Spray and so must have talked with Slocum at length at one point about the boat, so what if the assumed VCG was ALSO what Slocum's assumption, that Andrade based his calculations in part on what the sailor had told him?

    If Spray was less stable than Slocum thought it was it may have materially contributed to the loss. I know this is something we'll never know one way or another but it is something to ponder.

    This has been another completely random thought, now returning you to your regularly scheduled thread....
     
  7. GhostriderIII
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    GhostriderIII Junior Member

    That's what I would have done BEFORE making any changes. Too late now.
     
  8. jfrech
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    jfrech Junior Member

    Check this Front View out, now that looks like an extremely narrow tug for almost 38 feet long as well with respect to the amount of freeboard, as seen in the pic of the tug underway.
     

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  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Looks to be quite a lot of boat under the water comparing the two pics, I would hold off on fitting a large red panic button to the dashboard for a while.
     
  10. jfrech
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    jfrech Junior Member

    I figure about 3.5 to 4 feet under the water, you think that should be ok or by eye that looks adequate?

    Thanks for your intial responce, not sure if i m worring about nothing.
     
  11. TANSL
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    TANSL Senior Member

    I agree. Be careful because there's so much boat under the water that, perhaps, which is above water is not sufficient.
     
  12. JSL
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    JSL Senior Member

    It might still be a good idea to get a proper assessment. Probably a lot cheaper than an environmental fine or lawsuit if the boat should have an 'incident' due to stability or other issues.
    And if mv "Low Floater" sits low in seawater, it will sit even lower in fresh.
     
  13. nzboy
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    nzboy Senior Member

    I guess the litmus test will what she looks like in the water .My 2 cents after watching this post for a while is she is perfectly capable ship for her design parameters. I don't think putting a tall dog box and heavier motor would upset her stability to the point of being unseaworthy .With her low riding in the water this could be affected by ballast in Tads photo .If she is only 8 ton dry I suspect she would ride higher .Back to beginning of argument .Her beam is quite acceptable having a wider beam would increase initial stability but decrease ultimate. What do you want an ocean going self righting tug ? She would be quite happy in 1-2 metre swell. 4 metres ? I think you better look for a 20 metre tug .That being said the biggest factor in safety is her water tightness I mean you could install water tight doors and and windows with20mm glass if you had the money .Most boats that ply the seas have pretty poor stability very few with self righting potential especially if the doors are open .Most boats fill up with water due to poor maintainence or overloading for the sea conditions not design faults
     
  14. TANSL
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    TANSL Senior Member

    With the boats have to study many things before advising anyone to sail with them. A boat can have great stability and be a strong candidate to sink. Another boat may have very little stability but may be impossible to sink.
    Try to replace the lack of stability through watertight bulkheads or 20 mm glass is totally incorrect.
    Saying do not worry about the freeboard because stability is very large, is totally incorrect.
    No one has ever questioned the stability of the Titanic. she sank without a degree heeled.
    The "Erika" a very stable ferry, sank in a few minutes near the coast of Denmark.
    Be wise with boats, please. It is very easy to advise knowing that it is the neighbor who is going to sink .
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    What you say is fair comment, it is easy to counsel others with "don't worry about it ", but in this instance a thorough, properly conducted professional analysis of the situation is going to cost substantial money, it is either that, or the worry beads imo.
     
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