Multihull Capsize Prevention <split>

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

  1. CatBuilder

    CatBuilder Previous Member

    That might count. Do we have any info on the type of boat? Size?

    Although putting any boat into the steep breakers of a bar is a grave seamanship error, it could shed light on the discussion.
     
  2. waikikin
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    waikikin Senior Member

    Here power cats are used as high speed rescue platforms by our Volunteer rescue services & Police, Maritime services etc here's a vid.. http://www.youtube.com/watch?v=0CtedRYVF9U Doesn't mean they cant capsize. A good mate used to Coxswain a "Noosa Cat" in bright yellow/sprung seats/100s HP for surf, rock platform, & offshore rescue. Jeff.
     
  3. cavalier mk2
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    cavalier mk2 Senior Member

    You're right Oldsailor it was Glenn Miller but I read a recent study where a plane was reported spotted as the bombs where dropped. The quote was right though and illustrates the importance of heeding those nagging feelings concerning safety! The speculation about the out of fuel report was that it would be less demoralizing to the troops. No one really knows.....
     
  4. CatBuilder

    CatBuilder Previous Member

    That's right. It doesn't mean they can't capsize. I'm saying they haven't, and nobody has posted an example of one that has, so...
     
  5. MikeJohns
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    MikeJohns Senior Member

    That's more likely to make you less objective.

    This is a pretty fundamental question at the start of any vessel design; How far from the coast will it be operated?
    A Blue water vessel has a greater safety requirement to a coastal vessel not only for rescue concerns, but also access to both reliable weather forecasting and a safe haven within reach given a detrimental forecast.

    Wave statistics in deep water depend on the duration of the wind, the velocity of the wind over the water surface, and the fetch. Primary and secondary swell patterns are also dependent on proximity to land. So mid ocean is fully exposed blue water or however you'd care to describe it.

    The point about how many power cats was “what is their statistic representation in the data” compared to sailing cats in storms. Sure you can pick your routes and your times but it’s the smaller cats in rough seas that I’m talking about. Statistically they have had their share of inversions from waves.

    I don’t think you can argue that any sail area is overcanvassed. The examples I could give had some sail set since they were underway on sailboats. It’s easy to be an armchair expert and claim that the vessels were only lost due to the skippers lack of seamanship but I don’t think that’s fair.

    The MCA commissioned a detailed look at this in the 90’s from memory they wanted to quantify the risks from Wind and wave induced capsize in catamarans and then to tie that in tank test results for wave response. I’m sure Mr woods would be aware of those studies. They noted from memory that around 10% of cats inverted solely from wave action.

    The capsize mechanisms are well understood and the risks from surging and pitchpoling are quite high in sea states with wave height around the length of the vessel. In cruising cats this has been addressed with recommendations to lie to a drogue and cats have survived terrible storms with this method. But any skipper should understand the vulnerability of their craft.

    We should add collision induced capsize too.
     
  6. MikeJohns
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    MikeJohns Senior Member

    The bar was at low tide ebb so the water was relatively shallow and the waves were breaking, the cat pitchpoled while motoring in.
    It was a Lightwave 38.
    Examination of the boat hulls showed no contact with the bottom as there were some claims the boat must have nosed into the sand for this to happen. the mast did hit the bottom, but apart from a broken mast the boat was recoverable.

    A meta-analysis of accidents has been conducted before.
     
  7. MikeJohns
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    MikeJohns Senior Member

    Read what I said about power cats in my earlier post about them being more stable.

    Again, it's not a valid argument to compare a power Catamaran to a sailing catamaran. There is little similarity except in the number of hulls. The power cat will be around 25% heavier. The extra weight and often much lower CG makes a lot of difference to the seaworthiness.
     
  8. Corley
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    Corley epoxy coated

    I'm not sure absolutes are a good approach maybe a better way of looking at it is that catamaran capsize by wave action is a statistically very low probability relative to sea miles travelled?
     
  9. CatBuilder

    CatBuilder Previous Member

    That's pretty much what I'm saying. The probability is so low that it hasn't happened yet. Only performance cruising cats and racing cats have gone over due to sail handing errors. None of the capsizes have been due to sea state. All have been wind induced.

    Obviously, I looked into this quite a bit before deciding to build a performance cruising sailing cat.

    My new boat has the potential for wind induced capsize if sailed incorrectly.

    If I pull up the rudders and dagger boards, get rid of 100% of the sail area and just hide out below, there isn't much that can capsize the boat.
     
  10. CatBuilder

    CatBuilder Previous Member


    Incorrect. It was something I researched before deciding to build. It was researched with complete objectivity and I went through all the known capsizes. They were all sailing catamarans, either performance cruising or racing cats. All had too much sail up for the conditions and all were wind induced capsizes. Not a single one was wave induced. Wind induced capsizes are caused by operator error.

    As I said before, performance and racing catamarans demand the same respect an indy car, CBR 900RR, or drag racer might demand. High performance machines must be carefully operated. They present a great level of danger and are not very forgiving in inexperienced hands. They must be treated with respect and caution if you like living.

    All I can say here is that you are talking like a guy who works in an office (rather than at sea, as I do). Obviously we are only talking about boats that are capable of being "mid ocean" as you call it. My point is that term is a romantic notion with no actual meaning. It's something office people and people who do not spend time on boats say. It's what land people imagine in their minds when that "perfect storm" hits. It has no meaning as the worst of all waves do not necessarily happen "mid ocean." In fact, it is often very calm (too calm) during a crossing. From the posts above, we can see some of the worst of all waves happen right next to shore at an inlet. Pitchpoled at an inlet... now that's a serious wave.

    But I am digressing. The point is...

    You have failed to show a single instance of a wave induced capsize of a catamaran, be it power or sail.

    So what... not a single reference in your paragraphs above to what Richard Woods, one of the most experienced catamaran designers alive today says on the subject?

    Let me quote Richard one more time for you:

    ""Perhaps the most obvious statistic is that, to my knowledge, NO cruising catamaran has EVER capsized when under bare poles. To capsize with sails up implies a fair degree of "operator error", whereas its only when under bare poles that the boat MUST look after the crew."

    Richard's career designing catamarans spans nearly the entire modern catamaran era. Not only does he design his boats, but he has spent more time at sea in his own designs than nearly anyone I can think of.

    Here's another quote from his site (that I linked to previously in the thread):

    "Some years ago the Wolfson Unit at Southampton University conducted some model tests in their wave tank of both a power cat and a conventional deep V power boat to see which was the more stable in waves. People accept that a modern powerboat, like a Princess or Bayliner does not capsize, yet the test showed how EASY it was for a model powerboat to get rolled over by even relatively small waves. In comparison, NOTHING the Wolfson Unit could do would make the powercat capsize! Believe me, they tried everything!"

    The MCA tank test results you are referencing are either incorrect, or they didn't use an appropriate L/B ratio.

    Apparently, people who know and understand catamarans - people with actual experience crossing oceans in them (Richard Woods) - people who are world renown designers (Richard Woods) - people who have crossed seas in them (me) - people who work at sea in them (me) - do not agree with the conclusions you draw from your desk, as a steel boat monohull designer.

    I'm not going to pretend I know a lot about the nuances of steel monohulls. You probably shouldn't pretend you understand the nuances of catamarans.

    If there are wave induced capsizes of catamarans as you say there are, show us one.
     
  11. CatBuilder

    CatBuilder Previous Member

    Catamaran stability is determined by righting moment, which is a function of the hull spacing and buoyancy of the individual hulls. This isn't a monohull. If you want to read up on it, it's called "form stability" and it's the same thing that keeps your car upright when you go around a corner, as opposed to what happens in a motorcycle on the same corner. Google it.

    A power cat and a sailing cat are pretty much the same thing, except often a power cat will have a slightly smaller L/B ratio because it doesn't have a huge rig trying to tip it over. Extra weight is a liability in a catamaran, not a feature that makes it more "seaworthy."

    You really need to read up on cats. Nothing you are saying is right. I'm sorry, but it's not.

    Guess it's time to retire from this thread. It's getting a bit pointless to argue this topic based on conjecture and theory rather than fact and data.

    Fact: Still not a single example of wave induced capsize.
     
  12. Silver Raven
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    Silver Raven Senior Member

    Thanks 'Catb'

    Gooday & Thanks 'CatBuilder'. I sincerely hope that Richard (as in Woods) reads what you have said. Cause he's right !!! I more importantly hope & request - that everyone in this 'forum' place & other places in these 'forums' read the whole of the subject matter from the very beginning all the way through to the end. I feel most if not all people - will learn a lot - which is what is being attempted here - to learn - regardless of anyones personal ideas - we can all learn (even me - that's for Richard from me personally).
    If you want to learn from the discussion you have to read all of it. IMHO

    Cat - I agree - there is no - nor has there ever been a "mid-ocean" - what a stupid term - la- la land people say not-smart things. The danger with that is that they lead other less experienced people into danger & that may or will eventually cost someone their life. Not - IMHO - but fact.

    The only 'horrific' capsize - I can recall being mentioned in 1 of the forums,(which still scares me - big time) was a few years back of a cat - heading south - I think - just of the Central Western African coast - the boat got picked up & flipped - HOWEVER - the area the cat was in - is recognized as the most dangerous piece of ocean - in the world, or very close to the most dangerous. It's - from memory - rather close to the Western African cost (not "mid-ocean") I just can't recall - sorry - but I do know - that I put it into my mind to never ever go anywhere near there - which I had thought of doing previously to that.

    Cat - I'm not sure what caused it - as the last time I heard anything - they were still investigating the capsize. Probably a combination of many factors. A bit like - life itself. All I know is that - to be in that area in those conditions - in that boat - with that crew - I would have died - without doubt.

    Thanks for your input - again; 'Cat' thanks to you & thanks for quoting Richards very wise words of knowledge & hands-on experience - - sure hope Richard Woods reads this & I also hope others keep their minds open - - stop finding 1 word that is wrong & shooting everything down - including the messanger-boys - - open their minds & learn from the discussion.

    Best regards to all - ciao, james
     
  13. MikeJohns
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    MikeJohns Senior Member


    Now I'm confused, how does this differ with what I posted here:

    http://www.boatdesign.net/forums/mu...llision-survivability-38047-9.html#post556117

    I made the point that power cats were tremendously stable and I said why they are more stable than sailing cats.

    I made this point because you likened a power cat to a sailing cat with sails down which they are not, and I explained why.

    The MCA tank tests were to confirm the data collated from actual accidents so as to come up with a factual basis for assessing multihull seaworthiness. The study was conducted by Southampton, the same tests you are keen to quote (above). Have you read the report presented by one of the Southampton crew to one of the US sailing symposiums on this subject?

    As for examples I asked you a specific question, you didn't answer it. Before I post any vessel details of wave induced capsize, lets set the terms of reference first. I want to include cats that were under storm sails or even just a storm jib.

    It's supremely sensible to know the limits of the vessel you are on and not mislead yourself by collecting opinions that suit your prejudices.

    There are several wave encounters that can capsize a cat including the classic monohulls nemesis, the beam on breaking wave where a beam on breaking wave equivalent to the cats beam will usually capsize it.
    Once you accept the modes of wave inversion rather than simply denying them you might start to see how a small sail area would have almost no effect on a wave induced an inversion.
     
  14. oldsailor7
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    oldsailor7 Senior Member

    'Cat' thanks to you & thanks for quoting Richards very wise words of knowledge & hands-on experience - - sure hope Richard Woods reads this.

    I understand that Richard and his wife were caught in a mid ocean storm of such ferocity that they feared for their lives. They called a mayday and were taken off and the Cat was abandoned.
    Later, after the storm had abated the cat was found serenely sailing, all on it's own. Perhaps Richard himself could comment on this.

    In June 1981, John Hitch, Holly North and myself sailed from Sydney to Lord Howe Island in a club cruise, on board Johns Spindrift 45 catamaran"Hitch Hiker".
    The club cruise was a blow out, as 18hrs after the start a southerly buster blew in.
    The wind indicator showed 50kts gusting 55. We had 80 years of ocean sailing experience between us and we estimated (by judging from the height of the mast spreaders) that the waves were forty ft high.

    BUT they were also 400 ft long. The cat was on auto pilot on a close reach, with double reefed mainsail only. It would ride up the long slope of the wave smashing through the crest and sliding down the back in a flurry of foam.
    When the speed climbed to 18 kts we had reduced sail in stages in order to keep our speed down to a comfortable 11 kts and at no time did we feel in danger. This experience really reinforced our faith in a good catamaran to look after its crew in bad conditions.
     

  15. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Catbuilder,

    Do you know if cruising trimarans also are wave-capsize proof?
     
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