Multihull Capsize Prevention <split>

Discussion in 'Multihulls' started by MikeJohns, Jun 23, 2011.

  1. ImaginaryNumber
    Joined: May 2009
    Posts: 422
    Likes: 45, Points: 28, Legacy Rep: 399
    Location: USA

    ImaginaryNumber Imaginary Member

    News from Eclipse: Richard Woods Abandons Ship, 19th January 2006
     
  2. cavalier mk2
    Joined: Mar 2010
    Posts: 2,103
    Likes: 46, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    You guys need to mention center of gravity too. A power car with no rig and bigger engines and more fuel low needs less beam.
     
  3. MikeJohns
    Joined: Aug 2004
    Posts: 3,176
    Likes: 198, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Yes they are not equivalent vessels and the observation comparing power cats with sailing cats sans sails was flawed.

    I said before we could write a tome of Naval Architecture on the differences.
     
  4. MikeJohns
    Joined: Aug 2004
    Posts: 3,176
    Likes: 198, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member


    This might give you a good comparison, this is from Wolfston looking at 68 inversions there's a detailed report dated 1999 available from Wolfston.
     

    Attached Files:

  5. MikeJohns
    Joined: Aug 2004
    Posts: 3,176
    Likes: 198, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    I think you are deliberately misunderstanding the basis for all safety requirements. Which is proximity to the coast The likelihood of being caught in bad weather is very low for most power cats that I know of since they operate within 50 Nm of the coast and there is a nice service called weather forecasting. You missed the point I was making and concentrate on "mid ocean" just substitute with Blue water or whatever term you use culturally to denote unable to run to shelter.

    The breaking wave on a bar was due to the swell breaking due to shallow water, the point is that it's a breaking wave that is dangerous and it the owner perhaps believed some of the hype that gets posted about cats invulnerability to capsize.

    I don't want to post examples and have you say they are invalid because they had a small amount of headsail. So as I asked lets set and talk about terms of reference before I go to the effort of finding and posting recent accounts.


    Richard is a member of the forum, I would like to talk to him directly and in context, not through a third party quoting someone possibly out of context.

    Why? because the science doesn't agree with your opinion.

    It’s all naval architecture. Look at your logic here: Personal ignorance about something doesn’t extrapolate to another persons ignorance on another subject.


    You want facts but post third party opinions which are not facts. When facts that you can check are referred to you simply say they are wrong. So as I said, I want to know you will accept them. No sailing vessel underway in heavy weather would run without a headsail since broaching is a dangerous situation for a cat since beam on is a capsize vulnerability.

    Cats running under storm jibs alone have been violently flipped by waves, you could go and find the reports yourself.

    I re-iterate that your claim that no cruising cat has ever been inverted by waves is not only wrong, it's dangerously misleading. When they invert from breaking wave action it is in dangerous seas. The same waves make the upturned hull dangerous to be on unless it’s well designed for inversion survivability. There have been enough deaths where the upturned hull was untenable, emergency beacons unreachable and or rescue just too late. That’s an important consideration if people are going to be for example deep in the Australian bight or the Indian ocean or mid Atlantic where severe weather can not be avoided.
     
  6. ImaginaryNumber
    Joined: May 2009
    Posts: 422
    Likes: 45, Points: 28, Legacy Rep: 399
    Location: USA

    ImaginaryNumber Imaginary Member

    Thanks, Mike. Very interesting charts. I assume these are all sailboats, not powerboats? Do you know if these are cruising multis, or are racing boats included too? Do you know what the number of catamarans and the number of trimarans are for each piechart?
     
  7. Silver Raven
    Joined: Oct 2011
    Posts: 437
    Likes: 11, Points: 0, Legacy Rep: 67
    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Pie chart ???

    Gooday Mike. Thanks for the 'pie-chart'. Who came up with those figures ?? What is their professional design experience & how many ocean sea miles have they done.

    I'd sure like to hear what Richard Woods & Nigel Irens would have to say about the 'pies' analysis !!!

    Why are the 'pies' not covering the same subjects in the same language ??

    They don't use the same terms & I can't equate them against eachother in order to learn what I'm sure they want to teach me. Sorry I missed it but I'm to old & just want to go back on board & go sailing. Thanks for any help. Ciao, james
     
  8. MikeJohns
    Joined: Aug 2004
    Posts: 3,176
    Likes: 198, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    From memory:
    63 Catamarans and 67 Trimarans which had inverted. And all sailing craft over 10m. But this is heresay untill I either find the paper or get it again from the Wolfson institute.

    It clearly indicates that Trimarans give more warning in wind related capsize but in larger breaking waves are more vulnerable. But the best survivability for any multihull in heavy weather is to lie to a good drogue and maybe have a spare and look to your chafe guards.

    If anyone is interested there is an interesting phenomena with cats that doesn't apply to Tris in beam on inversion as follows:
    The cat can be knocked past it's AVS beam on by a breaking wave but doesn't go over because it's being pushed sideways quite quickly with a force below it's centre of mass, then the breaking part of the wave hits the lee hull and re-rights the vessel. This has been observed by sailors onboard in storms ( going over and then back) and has been verified in wave tank tests. But you'd have to be lucky.
     
  9. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    I’m not sure you understand statistical analysis.

    The number of sea miles is irrelevant. The quality of the data is relevant.

    They are a world renowned independent testing house, part of the industrial arm of Southampton University. Their knowledge and expertise is beyond compare.

    What someone has to say about XXX or YYY..is an opinion. What the facts show are irrefutable, these are “knowns”, as D Rumsfeld would say! A fact is known and widely accepted, and an opinion is based upon facts or subjective experience. Statistical analysis is based upon a collection of known facts without any opinion. That is in the conclusion aspect….an opinion based upon the facts.

    Thus I have no idea what relevance your question has to their “sea miles” credentials?

    I have the original 1995 report which the later, 1999 report is based upon; (which i also cannot find?) I wanted to post the report here but i keep getting a mismatch error report from BD Forum and it wont upload??

    PS...just realised why I can't uplaod the file. It is 18MB.!!..a tad over the 10MB limit :(
     
  10. Silver Raven
    Joined: Oct 2011
    Posts: 437
    Likes: 11, Points: 0, Legacy Rep: 67
    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Thanks Ad Hoc. I get it - or think I do. Still asking why the same terms - around the 2 circles aren't used??? I'm sure you'd know - cause all it does is confuse me. Ciao, james
     
  11. Gary Baigent
    Joined: Jul 2005
    Posts: 2,959
    Likes: 102, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Not sure quoting a dodgy war criminal is appropriate to this discussion point, Ad Hoc - but I take your humour.
    Another analogy is balanced viewpoint journalism - that also doesn't exist.
    The relevant point about facts is the "widely accepted" part ... until something or someone comes along and disproves it. Then there's a new fact. Cheers.
     
  12. Silver Raven
    Joined: Oct 2011
    Posts: 437
    Likes: 11, Points: 0, Legacy Rep: 67
    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Sorry to appear dumb BUT



    Gooday 'Ad Hoc' - just me again - the bloke - that - doesn't understand statistical analysis - Yea - Right - I personally think that you have a personality disorder - can't be challenged - can't have authority challenged.

    Last time I heard & read such - overall 'facts' was when 99% of the whole world said & I do quote - Multihulls can't go to windward - - multihulls can't point as well as monohulls. YEA RIGHT NOT

    I still do not agree with the 'facts' as you & them -'claim' as - Gawds-law - that is until tomorrow or the next day - when we all learn a new truth - Gawd man even Einstein admitted he would be found wrong.

    Oh & by the way - so are you - incorrect - that is !!

    Am I meaning to challenge you - you bet your last bloody GBP I am - you and all the other 1-eyed monstors with blinkers on. We'd still be paddeling 'river-pods' in the Thames if we all believed your mob. The world is round not flat.

    You have a grand day & enjoy your sailing - cause we'll enjoy our sailing c/w foils & wing-masts whilst going to windward - close hauled - at 1 1/2 times the speed of the wind.

    Ciao, james
     
  13. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Well, here's an extract, as an example (since I cant uplaod the whole report):

    Page 44  from 1995 MCA Report.jpg

    First line...breaking wave 1972, capszied after 3rd wave.
    Second to bottom line...breaking wave...capsize after structural failure.

    These are called facts.

    Not sure how you can disprove the attached later after the event?? :confused::confused:

    Seems you have a partner in crime Gary, who fails to accept "facts", you appear to base them on opinions....oh well. Your prerogative :eek:
     
  14. Gary Baigent
    Joined: Jul 2005
    Posts: 2,959
    Likes: 102, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Not disproving your list, Ad Hoc - and it is a list of "kindof" facts ... but not all the information is recorded - nor do I disbelieve that waves cannot invert multihulls, not my argument. However, reading the NZ listings, (pity the boat names weren't listed - immediately you are suspicious and question the substance of the "facts") ... for example one of the early capsizes listed, (I'm guessing from dates and boat length) was caused by a famous world girdling monohull sailor, here on a catamaran, confronted by savage winds and seas, reduced sail by tying a knot in his large headsail ... with predictable results. So just one example of not ALL the "facts" being recorded, kept quiet because of embarrassment - (and I'll bet there are others that are similar) but probably listed as inversion by wave or wind.
     

  15. CatBuilder

    CatBuilder Previous Member

    Speaking of statistics, I notice a trend here.

    The older, most experienced multihull designers and masters are posting one way, while the monohull designing desk jockeys are posting a different way.

    Perhaps they are frightened of the loss of office work in a monohulls design studio to the catamaran design studios? Maybe this is why they attempt to discredit catamarans, while never having actually sailed one?
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.