Multihull Collision Survivability

Discussion in 'Multihulls' started by Skint For Life, May 12, 2011.

  1. MikeJohns
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    MikeJohns Senior Member

    Not if safety is the main requirement of the SOR.

    The human operation of a vessel is a very significant factor. But sometimes unexpected things happen at sea, and/or the humans are too incapacitated to operate the craft safely. That’s where a quick self righting boat will always be safer than a non self righting boat by any sensible assessment.
     
  2. cavalier mk2
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    cavalier mk2 Senior Member

    Not if it comes up with a compromised deck and cabin and the fills and sinks. Or injures or kills its crew in the process both of which have happened. Better to dive for the hatch and worry about righting when things calm down. Rolling back up with the sails still set and no time to prepare is no good. Nor is being swept out of the cockpit and being pulled by the runaway. These things have all happened to monos working on automatic. You could fit a multihull with sensors and auto flooding/righting features. I think you'd be safer with a manual system.
     
  3. buzzman
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    buzzman Senior Member

    Provided you limit your definition of safety to "self-righting capability".

    For example, a multihull riding to a drogue or para anchor will be inherently "safer" than a mono in the same conditions, as the wider beam helps to prevent the excessive rolling monos tend to suffer from.

    This is "safer" for the crew as they are less likely to suffer falls or injuries as a result of the boat's heeling and rolling.

    I think we've acknowledged that the only real advantage monos have over multis is the inherent self-righting capability that comes with the counter-weighted lead keel design.

    However, I think it's also fair to say that a mono with a fast leak requires constant (and exhausting) pumping and baling, whereas a mono with such a leak - in the main hull - would be supported by the amas, and so not necessarily require pumping immediately.

    However, if the crew of the mono didn't pump/bale they'd probably sink, whereas the crew of the multi would in all likelihood, be much "safer" - as in: less likely to drown if they didn't pump/bale.

    Blanket statements like "a mono is safer than a multi" (or vice versa) are inherently unsound.

    I think we can agree that the monos self-righting capability is useful, especially as it will probably enable the boat to continue its journey, even under jury rig.

    But as far as "safety" is concerned, this is not the whole story.

    For example, an argument could be made that a multi with an EPIRB aboard is inherently "safer" than a mono without one.....

    But let's not go there, or we'll be to-ing and fro-ing like a Chinese ping pong tournament!
     
  4. boradicus
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    boradicus Senior Member

    Exactly
     
  5. CT 249
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    CT 249 Senior Member

    Great comment, Buzzman. Thanks for not being one eyed.
     
  6. buzzman
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    buzzman Senior Member

    A sailor is a sailor, whatever boat he/she chooses: mono or multi; dinghy or cabin boat; and whatever use they put it to: gunkholing on weekends; inshore/offshore cruising; inshore/offshore racing; single-handed or multi-crewed.

    Life's too short to focus on the differences.....

    Vive le vent! Vive la mare! Vive l'ocean!

    And death to all landlubbers.....!!!! :D :D :D

    Hah, harrr! Hah, harrr!!
     
  7. MikeJohns
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    MikeJohns Senior Member

    No! Once again they are completely different craft with completely different attributes. There are just as many reasons you'd choose a monohull over a multihulli as vice versa. It's only when you specify your SOR that you can clearly define what's better or worse and say why.
     
  8. MikeJohns
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    MikeJohns Senior Member

    Yes of course but again you are cherry picking. Decks and cabin tops can be, and are built to standards chosen so this will not happen. There are many racing monohulled sailboats that are deficient in deck strength that were designed to ABS OSRY scantlings. Earlier ABS rules were deficient in the keel attachment laminate requirements. By the same token numerous multihulls have suffered catastrophic failure from early scantling deficiencies before the loads were fully understood. But so what ? These arguments always take the best of one type and the worst of another.

    There is never anything safe about being in an inverted craft. A lot of people have been lost from inverted multihulls because there is nothing proactive you can do to go and recover them.
    For a multihull the moment it inverts it is essentially lost. It may be salvaged but it's a wreck until it's salvaged.
     
  9. redreuben
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    redreuben redreuben

    Could somebody clarify for me please, apart from the keel/self righting the advantages are ?
     
  10. redreuben
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    redreuben redreuben

    Oh fruit we're doing multi V mono again ! Oh well, aint going to go away !
     
  11. boradicus
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    boradicus Senior Member

    The title of this thread is "Multihull Collision Survivability." I believe it was meant to be a more pragmatic discussion about multihull survivability rather than a discussion about the merits of their survivability versus that of mono hulls. I think that is the point of the thread.
     
  12. cavalier mk2
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    cavalier mk2 Senior Member

    Mike you should read "Capsized" the book Callahan cowrote with one of the guys from the RoseNoelle, they came back in such good shape after over 100 days everybody thought it was a hoax at first. Compare it to the survival account of the people who were out there that long in a dink and liferaft after their mono hit a whale. I know which boat I'd rather have been on. With a manual righting system or parasail for inverted sailing they wouldn't have been out there that long.....

    I sail both multihulls and monos and think both approaches have merit. As far as safety goes our wing deck configuration makes everything so much easier along with not heeling. I've hung on in mast to the water knockdowns in monos while racing, they then usually spin out too and I can't figure out how this is inherently safer. Nothing like doing a head count while everyone is hanging by the lifelines or falling into the water. Again proper preparation and operation is key. A few years back in SF everybody was surprised when a well regarded and sailed boat disappeared while racing a 2 hand. They found the boat had lost its deck.....

    So this is a multihull thread and a collision one at that. Capsize can happen after collisions so it is worth looking at but monos are thread drift and not contributing much to the discussion.
     
  13. buzzman
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    buzzman Senior Member

    CM2

    I agree, with the monos getting involved in the thread it's drifting off course.

    If anyone wants to start a "Monohull Survivability" thread feel free to do so.

    I have been thinking about in-mast/on-mast inflatable bags that could assist with raising a multihull mast back at least to water level.

    I know there is at least one such commercial product available, the Crewsaver, but it is designed to remain inflated, and therefore affects wind over sail:
    http://www.crewsaver.co.uk/Crewsaver/Crewsaver_Leisure_Products/index.html?catid=46

    Farrier was designing a masthead inflatable system at Corsair in the early nineties, here's what he has said:
    http://www.f-boat.com/pages/background/capsizearticle.html

    My idea was along the lines of Farrier's system but to enable owners to DIY rather than have to purchase some super-expensive "product".

    Farrier mentions requiring 200lb to prevent capsize in an F-27...can someone who knows how to use a calculator tell us what they equates to in litres capacity....maths is *not* my strong suit....
     
  14. redreuben
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    redreuben redreuben

    91 litres
     

  15. buzzman
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    buzzman Senior Member

    OK, cool.

    My idea was to use a fibreglass SCUBA bottle - there is a small one that's used for back-up, but will need to check what it can handle in terms of volume, pressure etc.

    Lots of people go in and out of scuba as a sport, so 2nd hand stuff is often available relatively cheap.

    Then fixed copper or ally tube down the inside of the mast, with flexible armored tubes out of mast at base, threaded joiner, fixed tube into external access compartment containing cylinder with simple, basic, lever op ball valve.

    My idea was to have the system reversible, so that a vaccuum could be created in order to return the bag to its 'pack size' in order that it could be re-usable without having to climb the mast or whatever in order to repack it, and so it would progressively reduce in size rather than sudden decompression which could enable it to flog and get damaged....

    Anyone got any comments..? Preferably not *rude* ones...... lol
     
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