Making this boat self righting.

Discussion in 'Stability' started by zurk, Apr 22, 2014.

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  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I think you have the job ahead of you, self-righting powerboats are specialist designs that are tailored to that requirement, I doubt you will find a recreational boat that includes that capability. Yours could be the first. Not saying it can't be done, but it won't be err....a push-over. :D
     
  2. PAR
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    PAR Yacht Designer/Builder

    An oxymoron . . .
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    What might work, and I don't guarantee it, is a belt of bouyancy along each side, say from the gunwale about 2/3 of the way down to the chine, on the inside of the boat. Sufficient to float the boat, but not more than say, 10-15% over what is needed. Now, if you install bouyancy high up in the cabin, but only on one side of the boat, that imbalance, when the boat is inverted, should be enough to tilt it to the point where the lower side has no reserve bouyancy, and will go under further, and the boat *should*, assuming the COG is not too high :confused: right itself, but with barely any freeboard, and mostly full of water. Not much chance you will be getting underway with a drowned motor, though. Maybe that configuration of bouyancy will remain sufficiently stable for the boat to be bailed out. Or maybe not, depending on the sea state. However, if you get the sums wrong about the weights and flotation volumes, the whole lot could go to the bottom, or stay upside down . Someone may now like to critique the hell out of this idea. :D
     
  4. TANSL
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    TANSL Senior Member

    We had the solution in front of our noses and we were not able to see it.
    Cheers
     

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  5. zurk
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    zurk Junior Member

    well i'll remove the outboard and go to real world testing. try with 1000/1000 side and 200/200 top first.
     
  6. zurk
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    zurk Junior Member

    and the only reason you feel that way is because the boat industry is not mass market. can you imagine buying a car which had not been crash tested ?
    there is no reason a boat cant be safe when upside down and self right/remain stable when flooded other than the fact that designers dont want to sacrifice a non mass market expensive vehicle for getting data on an accident when their margins are low.
    i dont mind doing it because [a] im trusting this boat is built well and is new if its not i wouldnt want to trust my life to it anyway and [c] i have the equipment for recovery. of course no engines and fluids on board for getting damaged so i dont forsee any problems.
     
  7. TANSL
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    TANSL Senior Member

    zurk, in most cases, we are not the first to have an idea but it has almost always been someone who had it long before us.
    In ships, almost everything is invented. We can improve many things but there are few options to new things.
    In most cases, if one thing does not apply to boats is because, having tried it is not considered useful.
    You continue with your tests because of errors you can also learn. (And do not listen to anyone, okay?)
    Good luck.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    To illustrate a description I posted earlier, and I am not recommending you do this at all, but maybe is as idea that might work. A boat that has bouyancy tubes along both sides will be stable, like a catamaran when upturned, unless you restrict the bouyancy, and have the cabin flotation well off the centreline. Assuming the thing rights ( full of water though) it will become unstable as you bail it out as the boat rises, unless the buoyancy band on the side is distributed evenly in the vertical plane. Try it with a model in the bath-tub, if it doesn't work you probably have the mix of volumes/weights wrong, or it is a dud idea all round, which I then accept the blame for. :D
     

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  9. SamSam
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    SamSam Senior Member

    I have a problem imagining batteries and bilge pumps are even going to work at an 80 degree angle, much less pump out much water.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    Zurk seems to be in the business of telling what can be done, but asks how to do it.
     
  11. gonzo
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    gonzo Senior Member

    "there is no reason a boat cant be safe when upside down". I think you have obviously never capsized.
     
  12. Navygate

    Navygate Previous Member

    Zurk,
    I avoided this thread as the title seemed absurd.
    But today, I just had to peek..
    If you would allow, I'd like to make a few simple comments.
    There are less self-righting boats out there than self-righting.
    The ones that do self-right do so out of tremendous compromise.
    They also rely on a number of circumstances being maintained,
    like void spaces being kept... well, void, etc, etc.
    The idea, concept or fantasy of retrofitting a vessel to be self-righting is pretty far out there.
    Now, if an eager boat owner were to pursue it versus a Naval Architect it would be absurd.
    The best of luck to you.
    I hope you never capsize, I have and it's not good.
    :)
     
  13. PAR
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    PAR Yacht Designer/Builder

    I hope he does capsize, so he gets an idea of the dynamics involved. Preferably in something quite small, so he doesn't need a crane. Intending to capsize, say in a 12' dinghy, will offer a world of information. Ditto if the boat was swamped, yet still afloat. He'll quickly see why a swamped boat isn't stable, in spite of his best efforts. I've done both (more then once) and he'll be in for a rude awakening, when he leans over the side, to dump the first bailing bucket full of water.

    I think he just doesn't have any concept, nor understanding of the difference between a fully self righting craft and one that is essentially non-capsizable. You can have 120 -130 de3grees of AVS and still exspect to self right, because of the conditions associated with these events, which he also doesn't understand. He doesn't way to talk about why he requires this need, which is the real problem with this thread.

    Boats are designed for their purpose in life. Not having a clue about an SOR or this perception of selfrighting, over capsize prevention with an adequate AVS, he's going to run into this type of flack and negative response.

    Simply put, knowing the parimeters of the design requirements will yield the possibilities available. Not having as much as a clue about the SOR, he's asking for a crap shoot at invisible targets.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    There is a world of difference between a boat that capsizes and then rights itself, ready and able to resume its travels, and one that rights itself, but awash with water and the propulsion and other systems no longer functioning, and who knows what may have befallen the crew. It is very hard to see how the former is obtainable, without extraordinary expense, and the loss of much of its utility for normal uses.
     

  15. SamSam
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    SamSam Senior Member

    I have no idea how to design self righting, but I do remember an article years ago of a company doing a rollover test for a vessel they built for the Coast Guard that would be operating in one of those horrendous Washington state inlets where getting rolled over by the surf was almost normal.

    In calm water they pulled the boat 180 degrees over, expecting it to right itself. What happened was a fire extinguisher came loose from the wall and broke out one of the cabin windows, the cabin flooded and the boat remained upside down.

    So, as far as I can tell, having a cabin that remains water tight is the main, primary, essential, number 1 priority for a boat to be self righting.

    As far as I can tell, Zurks boat is an open cabin type boat with no serious capabilities of being watertight.

    The only way I can imagine making his boat self righting would be to install some kind of 'active' system that would automatically inflate bladders in the event of a capsize, something akin to air bags in cars.
     
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