Atlantic 57 Catamaran Capsized

[belizesailor]

Originally Posted by Polux

I don't believe in luck. I don't know of any Outremer that has been capsized and they are hugely more, (by a big multiplier) than Atlantic cats. If you say that the SA/D is about the same the explanation has to be somewhere and since beam is about the same (and probably CG too), weight similar, the only significant diference is a much bigger tripping surface due to those fixed keels.

Any vertical surface that prevents the boat to dissipate energy sliding instead or rolling has a negative effect on dynamic stability and on a light boat with a small inertia even more.

Of course in a sudden micro burst gust or an unseen spout at night, you are not going to have time to pull up boards.

Would be interesting to get Chris Ws perspective on this with actual numbers. Ive seen this theory discussed many times, but never a real world case or actual calculations.

[ALAIN97133]

I don't have time to read all the answers, but I can tell that if the "sailors" on board the cat didn't know that a gale blowing from the North or North-West against a strong current flowing toward the North can raise monstrous seas, they haven't done their homework before leaving. In November/December 2014, I didn't go on the "inside" (ICW) from Norflolk to Beaufort NC 'cause I love motoring, I only did it 'cause I wanted to stay alive

[belizesailor]

Originally Posted by Polux

[COLOR="Blue"]...

Sure, builders try to find always very rare meteorological phenomena to explain why their cats capsize but it is not credible that all 3 Atlantic that capsized had all been hit by rare weather events while Catanas and Outremer that outnumber them by 100 times, or so have, escaped miraculously to those phenomena.

Ana was not a rare weather event, nor did the designer or owner try to present it as such, but a very predictable squall...based on season, actual systemic weather conditions, and the fact that the owner described a classic pattern of a strong squall closing in on him. He had plenty of warning, plenty of time, but did nothing...never even eased the mainsheet.

From my perspective, user error was the cuase.

[belizesailor]

(deleted...wrong thread)

[SVNeko]

Originally Posted by Polux

Quote" After a conversation with the crew of Leopard I am convinced the inversion was caused by a microburst or extreme squall. There was no acceleration just before the boat flipped and it inverted almost instantly. They had eased the sails and decided to forego a sail increase until after dinner. The crew described a "roar" and we're immediately inverted. If it can happen to these guys, it can happen to anyone. They don't get more experienced or cautious than this crew. " Unquote

Yes it can have been a micro burst or a water sprout but being almost hit directly by one of those things I would say that they would have known clearly and would not raise the possibility of a big gust coming from a squall. On those rare phenomena after the huge wind goes away (after some short minutes) the sea becomes wild for a while, in my case with waves coming from different directions to the point I didn't know to where point the boat.

It is so unusual and weird that would probably have been refereed.

The explanation is probably the simpler one and the one that lead to the capsize of several big performance cruising cats, a sudden and unexpected big gust of wind provoked by a squall. That was the case with the Tp52 already mentioned, with that Australian cat can capsize in the River Derwent refereed on the beginning of the thread and also the case with the Atlantic 44 (probably also the other 57), and the case of a French performance, cat more than a decade ago, victim of a big gust coming from the mountains when he was turning a cape (with a very experienced crew).

Sure, builders try to find always very rare meteorological phenomena to explain why their cats capsize but it is not credible that all 3 Atlantic that capsized had all been hit by rare weather events while Catanas and Outremer that outnumber them by 100 times, or so have, escaped miraculously to those phenomena.

I don't believe in luck either, but I do believe in odds. And, albeit small, there is a chance that all 3 Atlantic cats just were in the wrong place at the wrong time. However, I can understand the desire to try to explain this seemingly high proportion of capsizes. I do not think the mini keels have anything to do with it though. I think the only way a sliding cat would dissipate energy would be by reducing the apparent wind by the speed of the catamaran sliding to leeward, which would be negligible. I do think AC cats are significantly lighter than Outremers.

As an aside, I wonder why APs aren't connected to wind speed information. I can imagine a helpful program linking wind and course where if the wind speed jumps by, say, 10 knots, the AP luffs the boat up if close hauled, or something along those lines - some helpful course alteration instead of just dumbly staying on course. Obviously, you should steer during a squall, but this could be a failsafe for those times when for whatever reason you are not steering.

[Polux]

Originally Posted by belizesailor

Of course in a sudden micro burst gust or an unseen spout at night, you are not going to have time to pull up boards.

Would be interesting to get Chris Ws perspective on this with actual numbers. Ive seen this theory discussed many times, but never a real world case or actual calculations.

Yes but actually the Atlantic has fixed keels plus boards. The daggerboards on an Outremer performance cat have a much smaller water surface compared with the fixed keels and boards used on the Atlantic:


Anyway I would like to correct some information: On that list of big performance cats I had given that had capsized due to gusts one of then was an Outremer 45 and I had said that I did not know of any Outremer capsizing.

I remembered the accident, remembered the circumstances and that it was a big performance cat but forget about the brand. I searched for it and found out that was an Outremer.

I don't know if the investigation of that accident was posted here. It has very good information. As I said the boat was sailing not far from the coast (2nm) to escape to waves, a distance they probably appeared enough (and to me too) to escape for most of coastal wind disturbances and gusts, but unfortunately it was not the case.

Passing a cap they were hit by a huge gust, released the main but was not enough and the cat capsized causing the death of most of the crew. The skipper and crew were very experienced ones with 40 000nm on that boat and two transats.

They say on the report that they had too much sail out and that the sail should be ajusted to gusts, but it seems unfair to me. On coastal conditions I have been on weird situations were the wind passes from 10 to 25k almost instantaneously, how can one adjust sail for gusts on those conditions? With the sail adjusted to 25k the boat would stay put in 10k winds.

Here is the investigation report:
http://www.bea-mer.developpement-dur...COEUR_Site.pdf

[catsketcher]

Thanks Polux for the info, I wish I could read French.

I think most catamaran designers would not try to distinguish too much between the Atlantics and similar cats like the Outremer et al. There could be something to do with the fineness of the hulls (the Atlantic looks finer) but really it is the centre of gravity combined with the centres of buoyancy that resists capsize - most similar cats have similar basic parameters. I would avoid making too much of the Atlantic capsizes unless someone can find a smoking gun.

It is possible for extremely unlikely events to happen more than once to the same group. Take the case of Malaysian Airlines. They lost a plane in mysterious circumstances (Australia is still looking for it) and then later one of its planes was shot down over the Crimea. Both incredibly rare events considering that there are about 1 million people in the air at any one time.

When I look at the Atlantics I don't see anything wrong - lots of boats have minikeels, they have wide beam, good steering position, high bridgedeck clearance, much more netting (that should increase stability in wind events) than almost any other cruising cat, low centre of gravity (again a good thing) and nice sail controls.

Maybe we should all be very concerned rather than saying - It won't happen to my condocat. If a well designed and built cruising cat of 57ft can capsize then we all can. In fact I think that capsize prep is poorly done on most cats.

Most cats will float very low after capsize. You can't stay in the hulls unless the boat has inverted flotation (Ana did). You must be able to access the liferaft on most boats and tether it to the cat. I don't see many people ever truly considering how they will deal with capsize anywhere near the way that our mono friends acknowledge the reality of sinking.

If you sail on a cat it can capsize. Prepare for it. Kankama has inverted flotation up the front so her bows will float high. We carry an axe to cut into the hulls to get into the sealed forward section. Most cats use the forward section for toilets and in hull stowage so they will float lower. These sailors will need to get into a liferaft/dinghy and work out a way to get into and out of the boat if they are going to use food and water from the mothership. What I am a little sad to see is people thinking that if they get a particular style of boat they will not be subject to capsize - its basic physics. Any cat can capsize. If something as well designed as an Atlantic 57 can then all of us on sub 50ft boats should be scurrying down to the boats and working out where to put the underwing lifelines etc.

I used to do a lot of writing for magazines and remember when the mag covered a production cat capsize on the Wide Bay Bar. The publisher got rung up by a very angry production cat builder (not the builder of the inverted boat). He made it very clear that his advertising money was not going to be forthcoming if we ran more articles of the same. I am not saying that the production builders will be doing this still but the lack of articles on capsizes of production boats could in part be due to very good PR departments. I would hope that sailors are clever enough to understand that there is no magic name of boat that makes them immune from problems at sea.

The again acknowledging risk can make people unsettled. When I was painting non skid on the bridgedeck bottom of Kankama a friend was worried and told my wife what I was doing. "Phil wants to capsize" he told her. Actually the thought scares me quite a bit. I just accepted it and dealt with it, he pretended it wasn't possible so he wouldn't have to deal with it. I think my actions were safer.

cheers

Phil

[JPA Cate]

I think my actions were safer.

I think so, too catsketcher, it seems quite prudent, especially since the hulls must of necessity be slippery. Your friend thinks you have an attraction to capsizing, but you're not alone in preparing for things we don't want to happen. Sometimes I wonder if a monohuller should mention something to a catamaran person.....

There's a flybridge Lagoon in the next berth from us. They do have a liferaft, mounted in such a way that it is not accessible from the cockpit, and will be in its cave under water if it were to capsize, trying to float up. I hope the owners are good swimmers, because they're going to have to dive and pull that puppy out. I hope it will slide out easily, but one wonders....... and I don't know.

Ann

PS, I did mention it, but I don't think the woman understood what I was on about.

[arsenelupiga]

Originally Posted by Polux

On coastal conditions I have been on weird situations were the wind passes from 10 to 25k almost instantaneously, how can one adjust sail for gusts on those conditions? With the sail adjusted to 25k the boat would stay put in 10k winds.

spot on. Now you get better idea for existence of condo cats. And it is not space. To suit non-alert, lazy crew. Lagoon can be turned around in 45 kn with full sails on, decent margin but not full proof. Not many turned, so i guess is good enough.

Cat paramters have changed and sucessive lagoon cats have less and less sail area and are heavier. Comparable perfomance to older models is gained by other means - stiffnes of the boat, better aerodynamics, etc.

Reality is, weather getting nastier, due to human interference, (10 B consumers) so boats must be more conservative.

[mikereed100]

Originally Posted by Polux

Yes but actually the Atlantic has fixed keels plus boards. The daggerboards on an Outremer performance cat have a much smaller water surface compared with the fixed keels and boards used on the Atlantic

They say on the report that they had too much sail out and that the sail should be ajusted to gusts, but it seems unfair to me. On coastal conditions I have been on weird situations were the wind passes from 10 to 25k almost instantaneously, how can one adjust sail for gusts on those conditions? With the sail adjusted to 25k the boat would stay put in 10k winds.

While the Atlantics do have mini keels, they represent a relatively small percentage of the total underwater surface profile. I may be wrong, but I doubt they would have much influence on static stability. Also, the fact that 2 out of 10 Atlantic 57's have capsized is too small a sample size to draw any useful conclusions.

The Atlantics are very well conceived and seaworthy boats and I don't think it is productive to look for a design flaw to explain the capsizes of Leopard and Anna. I think, instead, that it is more useful to keep in mind that boats on the performance end of the spectrum require more care and attention from the crew, especially when short-handed in unstable conditions.

Regarding the second paragraph above, I think most performance oriented cruising cats will move along quite well with a deeply reefed main and small jib. My own boat, which is somewhere in the middle of the performance spectrum, will do 4-5 knots in those conditions.

[Polux]

Originally Posted by mikereed100

...table conditions.

Regarding the second paragraph above, I think most performance oriented cruising cats will move along quite well with a deeply reefed main and small jib. My own boat, which is somewhere in the middle of the performance spectrum, will do 4-5 knots in those conditions.

You mean in 10k winds? But do you really sail coastly at 4 or 5K because there is the possibility of some gusts from the mountains when you can sail at 7.5 or 8K? And you do that for hours?

If so you are probably an exception, I don't believe that most that sail performance boats have that kind of patience or care sailing on zones where gusts can be possible, being it a monohull sailor or a multihull sailor.. Plenty of them on Greece shores, Islands and continent.

Note that there are plenty of cats sailing on those zones, also performance cats and I am not saying that accidents happen frequently, quite the contrary, they happen very rarely on exceptional but real situation and that is because those situations are very rare that very few will do as you suggest and will pass hours sailing at 4K with reefed sails on 10k winds, when they could sail at over 7 only because a very unusual and rare situation can happen.

[seaskip]

Originally Posted by catsketcher

Here is an interesting article that does include large and heavy cats in its talk about rig design. A fair way down is a section on cruising cats. Some of the basics are

- heavy and large cats have huge righting moment - the loads on flying a hull are so large designers can just assume the sails will be doused or blown out before you lift a hull.
- mast designers are not sure if this is a good idea

Info – AES

It would be interesting to do more research on the number of capsizes and the SA/D ratio (Bruce number). I can pretty much guess that the higher the SA/D ratio the more likely a capsize. It is basic physics. The question for me, and maybe others is, where is a cut off, over which you are unsafe.

It is a bit trickier than it sounds. Condo cats have a much higher centre of gravity than other cats. On top of this the loads and motion of a higher CG and heavy cat are much higher. High sheet loads may cause injuries and cause owners to be less likely to do things like reef or trim sails properly.

Multi designers have always wrangled with power and weight. For most of my time in multis we were always getting rid of weight - excess weight made the boats less safe - structurally and with the problems like bridgedeck clearance. The more modern cats handle weight so much better and yet it is hard for me to change my tune because I like the feel of a nice lightish cat.

John Shuttleworth designs performance cats and tris. He has a few good artiles on this. One here

Considerations for Seaworthiness

Interestingly when I use Shuttleworth's formula and plug Kankama's (my 38ft cruising cat) rough numbers in I get an answer that says I will fly a hull in 24 knots. That doesn't seem right. I will have to go out with a tape measure and have a check. I have never flown a hull in her yet (and hope never to get the chance). Is anyone else interested in plugging their numbers into the equation and getting some more answers?

cheers

Phil

Hey all,
I've done my homework FWIW.
It comes out something like this. I've used a couple of approximations erring on the cautious side.

From Shuttleworth design, with thanks.
Static stability is a measure of the stability of the boat in flat water, and is given by the following formula. (ref 2 )

equation1.................1
Where :
D = displacement (lbs).
CE = height of the center of effort above the center of lateral resistance (CLR) in feet. Use C of E to Waterline for quick calculation.
SF = windspeed in MPH that the boat has to reduce sail.
SA = sail area in square feet.
B = beam between the cenerlines of the outer hulls in feet.
This formula gives designers a measure of stability as an indication of the power to carry sail. i.e. the ability of the boat to resist capsize by wind action alone. There are two factors that can reduce SF. Firstly if the boat has a high angle of heel at the point of maximum stability, (worst in trimarans of type 2, and minimal in all catamarans) the correct SF is given by replacing beam in 1 with beam overall x cos(angle of heel). Typical values for SF can vary between 12 mph for a Formula 40 racing catamaran, to over 40 mph for cruising multihulls. Modern light cruiser racers would be in the range of 24 to 30 mph. So it is clear that in addition to the different types of multihull listed above the initial static stability can vary enormously.

My try at the equation for a Seawind 1160
D=22000lbs. Listed D is 7000kg or 15400 so I've added some cruising load.
SA=750 sp ft
B=16ft. I've seen 2 different figures for total Beam around 20-21'4" so...
CE= 25.5ft. All we could think of was to use a drawing of the sail plan from Seawind and scale it using the LOA of 38ft.
Ive tried to paste the formula but can't make it work, so here's my answer.
Reduce sail at 28.5 mph.
This is obviously amateur hour mathematically, but I'd welcome any comments or corrections.

[44'cruisingcat]

Originally Posted by Polux

They say on the report that they had too much sail out and that the sail should be ajusted to gusts, but it seems unfair to me. On coastal conditions I have been on weird situations were the wind passes from 10 to 25k almost instantaneously, how can one adjust sail for gusts on those conditions? With the sail adjusted to 25k the boat would stay put in 10k winds.

Here is the investigation report:
http://www.bea-mer.developpement-dur...COEUR_Site.pdf

One reef. Would easily handle 25 knots, and on that boat still sail quite fast in 10.

[44'cruisingcat]

The static stability calculations give a theoretical number, which is based on rigid sails sheeted straight down the centreline in beam winds.


In reality it will take MUCH stronger winds to lift a hull.

[Polux]

Originally Posted by ALAIN97133

I don't have time to read all the answers, but I can tell that if the "sailors" on board the cat didn't know that a gale blowing from the North or North-West against a strong current flowing toward the North can raise monstrous seas, they haven't done their homework before leaving. In November/December 2014, I didn't go on the "inside" (ICW) from Norflolk to Beaufort NC 'cause I love motoring, I only did it 'cause I wanted to stay alive

Maybe you should have read because there was no gale and the photo of the boat capsized taken from the rescue helicopter, some hours after the capsize show a flat sea.