Small boat underwater collision bumpers

Discussion in 'Boat Design' started by sailingsharky, Jan 19, 2018.

  1. sailingsharky
    Joined: Jan 2018
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    sailingsharky Junior Member

    Hey all. Well I'm absolutely no boat designer although I've drawn many, 3d modeled many, carved a few, and sailed a lot...however I have always wondered about the idea of a bumper -not as in an inflatable dock bumper, but rather an underwater bumper to help with underwater collisions.

    The most obvious design elements would seem to be hydrodynamics, practicality, and lastly a question that I would like help on - the probability of a specific bumper location (in my idea a strip along the center of the boat) being effective and the area most needing protection. In other words, given the probability of hitting a container, what is the probability of the center line of the boat hitting it vs the side of the boat hull being the primary destructive force point of contact?

    My initial idea was to actually have a pole which would serve as a crush zone - but more practically, I think that a strip of wood or crushable material along the centerline of a boat - a few inches thick for example may help such a collision and be very cost effective and not very visibly detectable. What are your thoughts?
     
  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    These guys could have used some collision protection.

    "Jan 15, 2018. Ray Roberts' Farr 55 Hollywood Boulevard sank in icy waters 150km east of Flinders Island on Sunday night. She was being delivered back to NSW by a crew of six after the 2017 Sydney Hobart Yacht Race. All crew members were winched to safety.
    Veteran of 40 Sydney Hobarts, Michael Spies, with 15 Hobarts and 1984 Olympic sailing representative James Wilmot, were among the crewmembers rescued by Air Ambulance. Spies told Channel 7 that he believes a collision with a sunfish early on Saturday morning was the cause of the incident. It is the second encounter with a sunfish for the yacht, which lost its port rudder after a similar incident in the 2014 Hobart."

    Sunfish blamed for loss of racing yacht Hollywood Boulevard off Flinders Island - MySailing.com.au http://www.mysailing.com.au/offshore/sunfish-blamed-for-loss-of-racing-yacht-hollywood-boulevard-off-flinders-island
     
  3. jorgepease
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    jorgepease Senior Member

    can't believe a sunfish sunk a boat... Instead of a pole you could angle the bow up so it actually exits the water and tries to ride over a semi sunken container. That won't protect keels or drives, what kind of boat you talking about, speeds ...
     
  4. rwatson
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    rwatson Senior Member

    Big lumps of cartilage - what are the chances they hit one a few years ago

     
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  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Running into anything that weighs 2 or more tons, at speed, will make a bad hair day for any skipper. The damage is dependent of how lucky or unlucky you might be at the time, but designing a yacht for every eventuality is simply impossible, unless you desire to sail at 2 knots, need 10 - 12 knots just to leave a slip and have three the money for construction, than another of similar size and configuration.

    Rub strips work, but hitting something doing 10 knots, that weighs 2 tons plus and you catch it in or near, the most vulnerable spot on the hull or keel, well shitt will happen. As far as inflatable bumpers and the like, you can do what you want, but how much would you like to bet the best designed set of bumpers, will still have a big fish or semi submerged container find the areas, just between the bumpers for the impact, just to show you who's really the boss, when in deep water, farther from shore than you can swim back too.
     
  6. JSL
    Joined: Nov 2012
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    JSL Senior Member

    much like automobile bumpers do little protecting in a 'crash', ... 'boat bumpers' would be similarly ineffective.
    Plus, they would be just another item to maintain
     
  7. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    Don't now which to marvel at most? The question or some of the answers. There are some serious issues of safety to be considered in designing a boat but this is not one of them.
     
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  8. sailingsharky
    Joined: Jan 2018
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    sailingsharky Junior Member

    And just to clarify you're stating this because you believe that the probability of a hull puncture is small in comparison to what you think the work required would be to prevent it?
     
  9. sailingsharky
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    sailingsharky Junior Member

    Given the shape of a hull (say without a keel and moving forward at 8 to 10 knots), can anyone step through the probabilities of the different parts of the hull and that location's likelihood of being the collision location?
    It seems like understanding the above would be core in terms of determining the practicality of a bumper design (i mean, either the whole front of the hull needs yo be protected - not practical - or not). Also I certainly don't think anything inflatable would be practical or effectual. A 2 to 5 ton boat moving at hull speed I think could use a few inches of wood as a crush zone to drastically lengthen the length in time of an impact. *If* it indeed was the component that hit said object.
     
  10. sailingsharky
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    sailingsharky Junior Member

    And of course my point here isn't to say that having and underwater collision bumper ( really, call it a super sized rub strip down to the keel) would be that much more important than proper rigging, hull design, or a working engine Etc. However despite the unknown but certainly low probability of hitting a container, I do believe that the probability will only increase over the course of all of our lifetimes. And it's something that I'm simply curious about, especially if there could be a practical solution that could possibly even be retrofit on existing boats.
     
  11. sailingsharky
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    sailingsharky Junior Member

    Actually, I'd like to know how much i should bet down to the cent. I am sure engineers working on car bumpers have researched just that.
     
  12. sailingsharky
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    sailingsharky Junior Member

    My interest is in sailboats, so your standard 30-40 foot sailboat. 10 to 15k pounds at 8ish knots.
     
  13. jorgepease
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    jorgepease Senior Member

    10,000 Shipping Containers Lost At Sea Each Year...Here's a Look At One https://singularityhub.com/2011/04/05/10000-shipping-containers-lost-at-sea-each-year-heres-a-look-at-one-2/#sm.0000p0ifmj62zfnfxz329rtu8365p

    It's not just shipping containers, collisions with whales is on the rise as well.

    The boat I am designing (catamaran) has a hull that gradually curves up above up the waterline before going in to an inverse bow. The sail drives are angled off the side of the hull so they don't extend below the hull surface. A sort of keel gives them a bit of protection from something like a log. If I was to ram a container just below the surface I would probably just ride up over the top. The rudder and centered dagger are kickup, the idea of a collision out at sea does bother me, I am taking all precautions I can though I don't think in my case a bumper is worth it.
     
  14. PAR
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    PAR Yacht Designer/Builder

    I've only hit something one, maybe a container, but it wasn't identified. It was a subtle but obvious bump that halved our speed, in the older wooden ketch I was delivering. My first response was to check for leaks and we found one, a good one at that. A sprung butt block on the planking was the result. So a centerline guard would have been meaningless, a forward positioned guard would have been also, as the impact was aft of midship, just below the turn of the bilge, well outboard of the centerline. Had the course been a couple of feet to port, we'd have missed it completely. Not a predictable location and unfortunate, as the butt block was difficult to access. The leak was plugged both internally and externally and we carried on. Our efforts caused other issues, but this was unrelated to the impact. You can't design for every eventually, but you can skipper for darn near most.
     

  15. tom28571
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    tom28571 Senior Member

    No.
     
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