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  #31  
Old 05-07-2009, 02:29 PM
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PAR PAR is offline
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I think some misconceptions should be dispelled.

Except for racers, which typically have a maximum positive righting moment in the 110 degree range, most mono's have 120 degrees or more. This simply means if you get knocked down, an occurrence much more common to mono's then multi's, you'll pop back up once the pressure eases. This is the case the vast majority of the time with a mono. Even if you do manage to turtle a mono, wave and wind action will usually roll her back over onto her belly. Of course any boat that experiences a roll, deep enough to immerse the rig, will come up with damage.

Going turtle in a mono is a very rare event, assuming your ballasted appendage hasn't dropped off and you're left with a very top heavy monolith to die in.

In the same vain, multi's by their very nature can't come remotely close to the extreme roll angles of a mono, without capsize at the very least, possible going turtle. Once turtled, the multi has a similar extreme initial stability value as if it was upright, making righting very difficult, if not imposable without assistance. Multi sailors know this full well and avoid these angles at all costs.

Many attempts to keep multi's from going turtle have been tried. Masthead floats seem best suited, if a bit odd looking, effective none the less. It's a lot easier to right from a capsize then a turtled position.

Statistically, multi's also don't experience capsizes very often. This is a result of several anomalies in the data gathering aspects of the statistics. Sailing relatively level in a multi, any heel over say 15 degrees or so and they get so nervous that they dump pressure much sooner then a mono sailor who wouldn't feel uncomfortable sailing at twice, possibly 3 times that angle. The fear of capsize and the comfort level inherent with multi sailing, usually forces them to avoid knock downs more then a mono sailor. As a result the statistics are slanted a bit.

Again statistically, neither mono, nor multi's go turtle very often. Most will never experience this in a life time of sailing adventures. There will be plenty of "horror" stories about rails awash in force 7 winds, all but the most insane sailor will sacrifice their sails before their lives. It's generally cheaper to make repairs to pride, ego and ship then have your family declare you lost at sea. This element of self preservation has saved skippers for generations, multi or mono.

Capsizes are equally as rare, but knock downs are fairly common. There are many mono sailors that will tell you of an incident where their spreaders touched or they buried the mast head, but popped back up once the gust was past. I know that I've had so much confidence in a boat that I was in, that I wasn't very concerned about a knock down. I knew the rig could tolerate it and that she'd come back up. Of course this is the wrong attitude to have in some sea states, but it's a common theme among mono sailors.

In the end you can live in fear or know your boat and personal skills as a skipper. Just like rogue waves (I've experienced one and seen another), these sailing events are very rare and you shouldn't focus too much on them, other to insure it's position on your priority list and it's related details (trap door, survival gear, etc.).

Placing your self in a dangerous position, such as sailing farther from shore then you can swim, inherently makes some desire the need for self rescue or other "feel good" element of the yacht design. The compromises we make to get to sea are the same ones we must accept in order to live with our decisions. If you're building a custom, you can raise the priority of capsize prevention up on the list. Of course as in all things in design, you'll have to sacrifice something in return. If you're working with an existing design then you are limited to the design brief established by the original concept, with the exception of a few upgrades. Learn to live with these compromises or select another design. Skipper skill and crew awareness are more important then design or equipment considerations, in the vast majority of incidents. When one looks at the reports of these incidents, it becomes obvious that there is a common theme and it's a human factor in large majority of cases. This is something that can be addressed, but most often is the one element of the equation that is over looked.
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  #32  
Old 05-07-2009, 04:45 PM
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rayaldridge rayaldridge is offline
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Quote:
Originally Posted by PAR View Post

Statistically, multi's also don't experience capsizes very often. This is a result of several anomalies in the data gathering aspects of the statistics. Sailing relatively level in a multi, any heel over say 15 degrees or so and they get so nervous that they dump pressure much sooner then a mono sailor who wouldn't feel uncomfortable sailing at twice, possibly 3 times that angle. The fear of capsize and the comfort level inherent with multi sailing, usually forces them to avoid knock downs more then a mono sailor. As a result the statistics are slanted a bit..
Well, that's true, but probably a bigger factor is that the stability of a multi is so much greater than a ballasted monohull of similar length. It takes a lot more energy to roll a multi than a mono. For example, in Chris White's excellent book, he compares a 50 foot cat to a 50 foot monohull. The monohull will put her rail under at about 70,000 ft lbs of righting moment. The cat will not lift a hull until it reaches 200,000 ft. lbs. of righting moment. Of course once that happens, the monohull's righting moment will begin to decline, but the cat's will drop very rapidly to nothing. The point is that getting to the danger zone requires much more extreme conditions, in a cat.

There's another element to this that I haven't seen discussed as often as perhaps it should be. When in a survival storm, the cat will be much safer when left to lie ahull. This isn't just because of its greater initial stability-- it's also because of its vastly greater roll moment of inertia. In the analysis of the disastrous Fastnet race in which a number of lives and boats were lost, it became apparent to the analysts that once a boat was rolled and lost her rig, additional capsizes became much more likely. This is because the CoG of the mast lies at a substantial distance from the roll center of the boat, and therefore has the leverage to resist sudden rolling forces, as would be encountered in a breaking wave. Consider that a cat, and to a lesser extent a tri has a lot of mass out on a substantial lever arm, and you can see another reason why multis are much less likely to be capsized by a breaking wave.

I'm not a fan of mast top floats, except maybe for boats intended for sheltered waters. The windage of a float, with its leverage atop the mast, seems dangerous to me. I know that wing masts can be dangerous in gales, for the same reason.
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  #33  
Old 05-07-2009, 06:26 PM
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A lot of tough lessons were learned from the race around the rock in '79. No designs since that era display those poor qualities. There were a number of reasons for the decline in yacht design, but rating rules and poor manufacture short cuts were the major players. Modern design don't have these bad manners in mono's.
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  #34  
Old 05-07-2009, 07:43 PM
Ad Hoc Ad Hoc is offline
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Just to throw a slightly different complexion.

HSC vessels for example, require reserve buoyancy built in. Range from 25% increase, for rivers, inlets etc, to 250% for offshore.

As for wanting/wishing to legislate for that "once in a life time" wave, pointless. This is all about risk and hazards of risks and performing a risk analysis of the vessel, its route the whole lot. Each risk is given a probability, with an associated acceptance or fail, just as in the aircraft industry. Fire regulations on HSC vessels are more onerous than an aircraft, because the philosophy is different and hence the risk is different. Everything in its place and context.

I was "fortunate" not to be on board a delivery trip of a vessel we had just designed. It was a 50m HSC catamaran on-route via the Yellow Sea. The boat was caught between 2 Typhoons. Encountered 10m waves for over 18 hours. The vessel didn't make much more than 2 knots head speed. But, being a catamaran, apart form the stiff motion (everyone had to lay down, couldn't stand up), the vessel was fine. Arrived at her destination somewhat later than expected, but with some minor cosmetic damage. The only reason why the vessel went to sea, when it should not have done (enough warnings about the Typhoons), was because the owner had just paid for the boat and had his own crew on board (as well as yard crew) and wanted the vessel in time for the major ceremony that had being heavily publicised for months. Major loss of face if it didn't arrive ontime.

Having lots of money to own a run a large shipping company doesn't mean one understands all the risks!
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  #35  
Old 05-07-2009, 09:48 PM
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Landlubber Landlubber is offline
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Ad Hoc,

How many times have we heard that story, after a while you learn to say "NO" to these people that insisy on leaving when we all know we should not.
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  #36  
Old 05-07-2009, 10:16 PM
Ad Hoc Ad Hoc is offline
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Landlubber
Well that is the whole crux of the problem.
When someone owns a boat and WANTS to do something despite the weight of advice from professionals, weather forecats etc, they can do so with impunity! They ignore the consequences....

Hence stricter legislation is the key, not designing for the once in a life-time/unsinkable boat...since accidents do happen. Just separate the real accidents (which are very very minor) from the pure negligent behaviour of others.
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  #37  
Old 05-07-2009, 11:08 PM
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It would have to be 99:1.

Sooooooo many times I see accidents waiting to happen, and yep, they do.
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  #38  
Old 05-07-2009, 11:41 PM
john.G john.G is offline
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Quote:
Originally Posted by Ad Hoc View Post
Landlubber
Well that is the whole crux of the problem.
When someone owns a boat and WANTS to do something despite the weight of advice from professionals, weather forecats etc, they can do so with impunity! They ignore the consequences....

Hence stricter legislation is the key, not designing for the once in a life-time/unsinkable boat...since accidents do happen. Just separate the real accidents (which are very very minor) from the pure negligent behaviour of others.
Under maritime law the decision as to whether to put a vessel to sea resides with the master not with the owners and/or agents. Because should the vessel founder then the responsibility is held to the master. Even if the master says "no" and is ordered to sea against his judgement, should the vessel fail then the master not the owner is held liable.

Of course saying "No" can get you sacked. Been there, done that - there's a whole class of commercial vessels operating in this area that I refuse to put to sea in as they are currently configured.
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  #39  
Old 05-07-2009, 11:58 PM
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Marshmat, I agree with much of what you say about PFD's but still think they're overhyped. For anyone who wants to go further into safety equipment discussion I've started a new thread:
http://www.boatdesign.net/forums/open-discussion/single-purpose-emergency-equipment-help-hinderance-27278.html

On multihull stability, I'm building my own boat with relatively low tech materials. Doing all my own labour, materials are my biggest single cost. I can afford 4 tons of "raw" boat, which gives me (very roughly) a choice of a 28" mono or a 45" cat. I'll give people one guess which I think will be more stable in large waves.

It would be nice to see some more data on how much work to tow over a multi - I've wondered about a sea-anchor and electric winch or big outboard on the dinghy might do the job if used with a block and tackle. I agree with PAR that righting at sea is more about psychological security than actual likelihood though.
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  #40  
Old 05-08-2009, 12:41 AM
catsketcher catsketcher is offline
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Don't worry about self righting

Gday all

Multis went through the self righting phase in the 70s and 80s. Dereck Kelsall made a workable 35ft cat that actually was built and tested by Gunter Ullrich. Multihulls magazine published a whole book called "The capsize bugaboo" which had lots of different theories in it. Yet the emphasis shifted to different areas, why? Because cats don't capsize often at all, so why have huge amount of effort and money tied up in something that will occur rarely?

Saying this I put my money and time into capsize strategies as drawn by my cat's designer Robin Chamberlin. He was surprised when I asked for inverted flotation and full bullheads fore and aft as he said that most consumers ask him to take them out. I don't know why. Having the ends of the boat sealed off from the accommodation robs me of two hard to use beds but means the inside of the boat never gets wet, I get large gear lockers, airflow in rain, and the peace of mind that if the worst was to befall us we would have a very large mothership to live on till help came.

Someone is probably going to get upset at the mention of help but it is a reality that help is more easily summoned now than at any time in the past. I just have to give people a long time to be able to get my family off when conditions are safe.

It is very easy to get a cat ready for inverted life. Put your batteries outside, put vents on your water tank breathers and fillers, build in a nice bottom (inverted top) to a bow locker, divide the bows and sterns off from the accomodation (leave seal able air vents), leave an axe near your outboard pod (when offshore), put non skid on the bridgedeck bottom (makes fairing unecessary) get netting ready for your food lockers. If the worst happens you will have a hard time (waiting inside) until the boat settles and then you chop a hole up the front under the bow locker floor and jump in. Your calamity pack goes with you and you turn the EPIRB on. Hell on my boat I even have the SSB radio mounted low so it may be above the inverted flotation line. It hides away so that no one would know I have an SSB if a thief was looking.

Read books like Chris White's and Jim Brown's. They deal well with survivors of capsize. Try and get the Capsize bugaboo and when building think of how you could make your cat float higher when inverted.

All off my cat's features make her safer right way up too. She is one of few 38 footers that you could punch a hole in and stand a 45% chance of getting a watertight compartment. In fact you could chop the front 3.2m and back 2 metres off and not get any bilgewater in the main bilges. AND there is very little consequence of this to amenity - she is a great boat to live on because of the safety features - it means wet sails, garbage, resins and fuel smells never make it inside.

These are safety features I have installed on my family cruiser. You may be able to think of more but as you build a boat make sure you don't drastically reduce your boat's safety for some nebulous interior gains.

cheers

Phil Thompson
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  #41  
Old 05-08-2009, 05:56 AM
Ad Hoc Ad Hoc is offline
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john.G

Yes i am aware such rules. But here in Asia, such things tend to be looked at differently, shall we say. The Master would not have been the only one to loos his job if he didn't sail, his whole family etc. The owner of the vessel, whom also owns the operations side, pretty much owned the whole town..a major big wig. One doesn't say no!

Having said all that, that is the commercial world. This post is ostensibly about pleasure/leisure/personal/private craft. As such these maritime rules/laws "generally" don't apply. Try applying the law to a guy on his jet-ski who went too far out, got caught in the main channel current, or a the lone sunbather on his inflatable bed fell asleep and drift way offshore.

These very same people are bound by laws/rules of society such as when the get into their cars, or walk around in general. Why should being in/on the water be any different?
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  #42  
Old 05-08-2009, 09:41 AM
Boston Boston is offline
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because its just kinda assumed that stupidity rules
get on a boat and leave your mind behind seems to be the rule of thumb
happens so regularly its become whats expected
I might have mentioned that it was a miracle any of us cape kids survived growing up with the ocean out the back door
I little good old fashioned fear of the water is what most people lack is what I always noticed
gets em in trouble all the time
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  #43  
Old 05-08-2009, 10:25 AM
john.G john.G is offline
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Quote:
Originally Posted by Ad Hoc View Post
john.G

Yes i am aware such rules. But here in Asia, such things tend to be looked at differently, shall we say. The Master would not have been the only one to loos his job if he didn't sail, his whole family etc. The owner of the vessel, whom also owns the operations side, pretty much owned the whole town..a major big wig. One doesn't say no!

Having said all that, that is the commercial world. This post is ostensibly about pleasure/leisure/personal/private craft. As such these maritime rules/laws "generally" don't apply. Try applying the law to a guy on his jet-ski who went too far out, got caught in the main channel current, or a the lone sunbather on his inflatable bed fell asleep and drift way offshore.

These very same people are bound by laws/rules of society such as when the get into their cars, or walk around in general. Why should being in/on the water be any different?

Yes I understand that. Here isn't that different. I was blacklisted out of an area of the industry here as a troublemaker for my stance on the issue I questioned.

My biggest fear at sea is not rogue waves, cyclonic conditions, container strikes or being trodden under the forefoot of a supertanker. It's the fools cutting under my bows in a speedboat that I'm going to kill one day. The law of the sea does apply to them - it's just that no-one seems to enforce the law, and the fools themselves don't know the law.

Ultimately it is impossible to regulate against stupidity. Just most of the fools are lucky, and some of them aren't.
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  #44  
Old 05-08-2009, 02:52 PM
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Richard Woods Richard Woods is offline
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In 1979 three of us had just crossed the Atlantic and were crewing on a Frers One-tonner in Cowes Week. As the week drew on we realized just how unseaworthy the boat was and that the owner and his friends (the rest of the crew) were very inexperienced. There was a “Solent gale” on the Thursday and we had to retire from that race. The owner was still keen to do the Fastnet race but we said we wouldn’t do it. Fortunately we managed to convince him to withdraw. The boats we were racing against were all of a similar standard (both in terms of the boat and crew experience). Sadly, as we all know, it was these boats (Ariadne, Grymalkin etc) that came to grief a few days later. To us it was no real surprise, given the conditions they encountered.

A couple of weeks later I started work for Derek Kelsall on the very day that Gunter deliberately capsized and re righted his 35ft catamaran (in a lake next to Derek's yard). It has never capsized when sailing (of course) yet the design was very compromised to make it self right. I saw it sailing in the Caribbean in 2003.

Having been in a survival situation I can say that what you think and plan to do in the comfort of your office or armchair is not what happens in reality. If you have a fire at home do you try to put it out yourself, or call for help? Why do governments invest huge sums in SAR, EPIRBs etc if they don’t expect/want people to use them??

Florida has some of the toughest enforcement of Coastguard regulations in the USA. People have been fined for not wearing lifejackets on a short dinghy ride to shore. Yet this is a state where you don’t need to wear a crash helmet when riding a motorbike. Something to do with “civil liberties”. There are a lot of very stupid motorbike riders in Florida. Fair enough, they are all skilled riders – of course – but it is the other vehicles they met on the road that will kill them or leave them paraplegics.

As far as unsinkable boats are concerned, I copy this from another forum where I wrote

“News from 1992
From a fax from Pete Benjamin, of Heritage Manufacturing, the S-African builders of the Sagitta: " My charter Sagitta Bojangles was put on the rocks at a place called Rooi Els. The charterers claim the anchor rope parted at 3am and they were awakened by horrible sounds of the boat grinding on the rocks. To cut a long story short, when the tide went out they effected emergency repairs and the Sagitta was refloated on the following high tide by crowds of people - minus a keel and a badly damaged starboard hull as well. They motorsailed to Gordon's Bay and although the modules were awash the bloody thing didn't sink!!!!' It made national TV and I think that the safety aspects of the watertight compartments are not to be overlooked as is the incredible design feature that led her to being such a safe boat - Thanks folks!”

I say a lot more in my Perfect Storm articles, see the Articles section of my website.

Richard Woods of Woods Designs

www.sailingcatamarans.com
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  #45  
Old 05-08-2009, 04:47 PM
ImaginaryNumber ImaginaryNumber is offline
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righting by stern over bow

Quote:
Originally Posted by bad dog View Post
is there any value in discussing how to get the mast skywards again?

Here is Tony Bigras's idea for a stern-over method:
Flood bows
Use weighted lever to pull sterns over bows
Pump bows dry

http://www.ideaintegrator.com/boats/o7/flipper.htm

main site for aluminum cat Osram VII
http://www.ideaintegrator.com/boats/o7/o7.htm
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