Atlantic 57 Catamaran Capsized

[catsketcher]

In going from 10-25 knots there is not much difference between monos and multis. Both will have trouble dealing with quick changes. If we have large sails up for 10 knots interesting things will happen no matter how many hulls one has if you get hit by 25.

Of course if we are worried then we can use a sheet release system. I have never used an automatic one, or even seen one in the flesh. I do carry one though - it's called ME. I can release my main in a second or two. Around the Whitsunday Islands we get large gusts - the locals call them bullets. Some anchorages like Stonehaven are notorious for them. Once in 2014 we were sailing past Stonehaven with staysail and reefed main when I saw a gust whipping water into a vortex of about 30 metres height. It was far enough away for me to turn the boat downhill as we were hit by the gust. Nothing special just normal catamaran/dinghy sailing technique. Stay far enough away from land to windward so that you can see the wind - track the gusts and you are fine. At night be careful and consider reefing.

In the case of Ana the owner probably turned the wrong way. Unless you are already close to the wind it is usually better to bear away. There is a region called the death zone by skiff sailors where you can head up or down but you don't want to stay in this angle in big winds. It is usually a beam reach. I find dumping main and bearing away very easy to do and it gets me to safe deep angles quickly. Steer with the mainsheet first just like in a dinghy - don't bear away with sheet on.

All of our boats require care and attention. A heavy cat will have loads that scare the bejesus out of me but if the owner is happy that's fine. Just today were were sailing upwind in about 20-22 knots doing 8-9 on the GPS with the staysail and full main - a child could have winched our staysail on - that is a safety feature I value hugely. The main doesn't even have a winch - just a 4.1 sheet so it is really quick to adjust. (The wishbone takes almost all the leech loading so the sheet loads are reduced dramatically - like vang sheeting a dinghy.)

Safety isn't just about how much wind lifts a hull. It's about sheet loading, ergonomics, windward ability with and without a motor, ability to set a proper storm jib, handholds inside, manoeuvrability, ability to be holed and sail on, lack of pounding, steering visibility, providing a safe platform if inverted and more. Focusing on one facet gives an imprecise description of how safe a boat is.

cheers

Phil

[seaskip]

Agreed 44 and Phil. I certainly wasn't thinking there was any magic to a number. A very interesting calculation though. And a way of looking at stability for a cat. I learned stability as part of my studies, but it focused on loading conditions and cargo. Aimed more at commercial shipping.
Wind at your back
Btw, Phil, your Stonehaven story bought back some great memories. I sailed backpacker charters up there for a while, and remember getting quite a laugh as those bullets sent books, hair and swimwear flying.

[Polux]

Originally Posted by arsenelupiga

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.
...

Where do you have got that number regarding a Lagoon only capsizing with full sails with over 45K winds?

In fact I think that it should be mandatory that information (the wind needed to capsize a given cat with full sail) on the information given by the builders regarding a boat, the same way on a monohull the AVS should be provided.

The truth is that is not mandatory and very few monohull builders give that AVS information (Halberg Rassy and Elan are among the ones that provide that information without having to be asked for) and I don't know of any cat builder that discloses the information regarding the wind needed to capsize a given cat with full sails.

Maybe I am wrong, did that information regarding the wind needed to capsize a Lagoon (+45K) come from the Lagoon shipyard? Or from the designers (VPLP)?

There are some simplistic formulas around that are supposed to calculate that (as there is some to calculate monohull AVS) but not only the data to use them cannot be assessed without precise calculations as the results given are not accurate and can be way off.

The calculation implies the use of a righting moment curve that will give the means to calculate the energy to capsize a cat and then the calculation regarding the rotational energy provided by a given sail design with a given area, that equals the energy needed to capsize the boat. Not an easy calculation even if not hard if you have all the data needed to perform it, but one that would take a considerable time if you don't have the computer programs to make those calculations easy.

All NA make these calculations when designing a boat and are based on that they will determine the sail area a given sailboat can carry safely, being a more conservative one if it is a cruiser, a more liberal one if a performance cruiser.

Getting back to those +45K that you say are needed to capsize a Lagoon with full sail, if it was so the boat should take the first reef at near 30k, the second at 40k, the third at 50k, only third reef and no frontal sail at 60K and bare poles over 75k, assuming that a cat should be reefed for gusts and not for real wind. This would give a very wide safety margin. I assume that those +45K were true wind so I am talking about true wind either.

In fact if we look at the manual of a Lagoon 400 we will see that they say that the reefs should be taken incomparably earlier. They give the wind speeds at one should reef in apparent wind that when going upwind is significantly less than the true wind and they say that in rough seas situation the reefs should be taken 10% earlier.

For a close hauled situation, were the apparent wind is substantially higher than the true wind, what they say is this:

" CLOSE HAULED TRIMMING (between 75 and 50° to true wind)
Given wind force in apparent wind
- From 0 to 16 knots: full sail ;
- From 16 to 20 knots: full sail ; the mainsail traveler moves up to 60
cm to windward of center, mainsail trimmed with a slightly more open
leech ....
- From 20 to 26 knots: 1 Reef, full Genoa
- From 26 to 30 knots: 1 Reef, 75% of the Genoa ;
- From 30 to 36 knots: 2 Reef, 60% of the Genoa
- From 36 to 45 knots: 2 Reef, 40% of the Genoa.
- From 45 to 55 knots: 3 Reefs main alone
- Over 55 knots: lie to, drag anchor or, preferably, scud bare poles

As you can see there is a huge diference on those numbers. I was talking about near 30K real wind (about 34k apparent) for the first reef while on Lagoon they consider 20K apparent for the first reef.

Those Lagoon reefing numbers don't add up with a catamaran that will only be capsized, with full sails by a wind of 45K, much less to a cat that "can be turned around in 45 kn with full sails on, decent margin".

Having wrong ideas about the wind a cat can sustain with full sails without capsizing can be very dangerous since it will induce a confidence based on unreal facts.

Note that I am not saying that a condo cat is not inherently more safer than a performance cat neither that it his easy to capsize a condo cat. In fact the numbers show, given the big disproportion in numbers between condo cats and performance cats, that the capsizes of cruising condo cats are much less frequent than the ones of performance cats and they tend to happen in smaller than 50ft cats, the smaller the more frequent. I don't think I have have heard about a bigger than 50ft condo cat capsizing, but I may be wrong.

[Polux]

Originally Posted by catsketcher

In going from 10-25 knots there is not much difference between monos and multis. Both will have trouble dealing with quick changes. If we have large sails up for 10 knots interesting things will happen no matter how many hulls one has if you get hit by 25.

That is not true. I never take full sail on those conditions, no need to.

Normally the first need for a reefig most monohulls is around 18/20k, 25K is not far away from 20k and on gusting situations what you would get on a monohull is sudden acceleration accompanied by some ocasional deep heeling that will spill excessive wind from the sails. If the gust is a prolonged one what you will have is the boat losing rudder control, turning to the wind, before the autopilot assumes control again and brings the boat on course again. It is never a dangerous situation.

Much more fun doing that at the wheel and not on autopilot and with two, as it is our case, it can be a very rewarding sailing situation, lots of fun for the ones that like sailing, adjusting at each moment the traveller and the mainsail to prevent the boat from heeling too much transforming all those gusts in boat speed.

On a cat the boat cannot deep heel to spill the excessive wind out and what is for some an inconvenience on a monohull (fun for others) can be dangerous on a performance multihull.

Don't think those conditions can raise a real danger on a condo cat that will need much more wind (with full sails) than a performance cat to capsize. They will just turn to the wind at the first gust and will reef sails for added safety.

[ALAIN97133]

Originally Posted by Polux

If you are talking about a cat the same size of your boat than you are right but a big cat has a huge stability and in what regards the energy needed to capsize it it is much, much bigger than the one needed to capsize your boat...and when a boat capsize all sort of things can happen,... On a monohull a fast performance boat can have the same stability or more than an heavier boat due to a better B/D ratio and a deeper keel with a torpedo keel. that does not happen on a cat unless the performance one is much more beamier and that is not normally the case.

"On the probability of occurrence of rogue waves"

http://www.nat-hazards-earth-syst-sc...2-751-2012.pdf

[Polux]

Originally Posted by catsketcher

...

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. ...

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.
...

The Malayan airline case and the Airplane shoot over Crimea had nothing to do, they were not accidents in a sense they were provoked and had nothing to do with the airplane itself or its correct functioning (new data on the Malayan case).

I agree that it is very rare unlikely events to happen more than once and that is why that 3 capsizes on big Atlantic cats are highly suspicious. That should not have happened by all the probability laws and justifies to look at those boats to understand why.

It is known that on a hull all vertical underwater surface that makes more difficult a boat to dissipate sudden energy of a wave or of wind by moving laterally has a big negative effect on dynamic stability. That can be compensated by a better static stability but on cats with very low weight (performance cats) that does no happen, increasing the risk factor.

I cannot see any other difference between the Atlantic designs and other production performance cats than those long fixed keels and I believe statistics are not to be dismissed in this case, as you say, it is extremely rare unlikely events happen several times on the same design and not in others, at least in any similar percentage.

Regarding condo cats capsizing, I don't know of any with over 50ft to have capsized, I mean ever. Maybe I am wrong, do you know? While I know at least three performance cats over 50 ft (two with almost 60) that had capsized. Given the huge disproportion regarding condo cats and performance cats those numbers assume statistically a big relevance and I believe that it is correct to say that facts prove that condo cats are inherently more safe than performance cats.

Not saying by any means that performance cruising cats, over a given size depending on the use) are unsafe but they are less prove error, demand more attention, need a bigger crew for that attention to be possible and effective and are less forgiven in what regards weird wind phenomena.

We can say that if a performance cat is sailed in not a performance way, very conservatively, than it is as safe as a condo cat, but then what is the point in having a performance cat?

Look at this year's ARC, you have a 60ft Outremer 5x that is going slower than a Lagoon 42, I guess the ones that sail that Outremer follow that principle, but then why they have spent much more money buying an Outremer 5x if they could have a Lagoon 62 for half the price, with a much bigger interior space and load ability? And by the way if the Lagoon 42 is ahead, there is on the ARC one Lagoon 62 way, way ahead!!!

[boatman61]

Originally Posted by topmast

Back in'68 the schooner Bluenose nearly sailed herself under same area. Moderate night, sudden major wind .no time for crew to react, Fortunately sails left their bolt ropes and it was over

I suffered a knockdown in that area on a 54ft Bruce Roberts steel ketch.. drifting along in a light SW with all sail up.. then a hell of a gust from the N out of nowhere.. we were just doing the midnight changeover when the boat decided to rinse the sails..
Bounced right back up when I released the mainsheet and genoa.. but boy did it accelerate the heartbeat..
Blew a steady 7 for the rest of the night after that intro..

[SVNeko]

Originally Posted by Polux

I agree that it is very rare unlikely events to happen more than once and that is why that 3 capsizes on big Atlantic cats are highly suspicious. That should not have happened by all the probability laws and justifies to look at those boats to understand why.

It is known that on a hull all vertical underwater surface that makes more difficult a boat to dissipate sudden energy of a wave or of wind by moving laterally has a big negative effect on dynamic stability. That can be compensated by a better static stability but on cats with very low weight (performance cats) that does no happen, increasing the risk factor.

I cannot see any other difference between the Atlantic designs and other production performance cats than those long fixed keels and I believe statistics are not to be dismissed in this case, as you say, it is extremely rare unlikely events happen several times on the same design and not in others, at least in any similar percentage.

The third Atlantic cat was a 42 and it happened a long time ago. If you bring that one into the statistics then the base is much bigger as there are a good number of Atlantic cats out there if you count all sizes.

Again, you are mixing apples and oranges talking about underwater profiles. It may have an effect for a wave strike. But a wave-induced capsize is almost instantaneous and there would be no time for the boat to dissipate energy by sliding to leeward. The only effect would be a very slight diminution in the apparent wind from the speed of the sliding, which is negligible. It doesn't change the geometry of the forces at all.

And there are plenty of cats with keels and big rigs that, according to your theory, should be tipping over all the time. So even though they seem like extraordinary odds, I chalk this up to just bad luck.

[Cottontop]

Originally Posted by Polux

Normally the first need for a reefig most monohulls is around 18/20k, 25K is not far away from 20k and on gusting situations what you would get on a monohull is sudden acceleration accompanied by some ocasional deep heeling that will spill excessive wind from the sails.

The power in wind is a cubic function of velocity. Tremendous amount more power in 25k than 20k (maybe almost double).

[robert sailor]

Originally Posted by Cottontop

The power in wind is a cubic function of velocity. Tremendous amount more power in 25k than 20k (maybe almost double).

You may be right as to the wind power but Polux speaks the truth. Having the wind gust from 20 to 25 on a cruising mono hull is no big deal and very easy to deal with even if well over canvased.

[mikereed100]

Originally Posted by Polux

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?

Absolutely, and have done so many times. Why take chances?

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..

You are probably right. If so, and they get into trouble, then that is on them.

We have a hard and fast rule aboard that when we are sailing in the lee of mountains and headlands we are deeply reefed and have our small jib up. Our static stability with this configuration is 51 knots. Sure, it makes us slower, but we are cruisers, not white knuckle sailors. On the other hand, I would happily sail fully canvassed on your boat in those conditions. I'll bring the beer and Cheeze Whiz.

[mikereed100]

Originally Posted by robert sailor

You may be right as to the wind power but Polux speaks the truth. Having the wind gust from 20 to 25 on a cruising mono hull is no big deal and very easy to deal with even if well over canvased.

True, but is should not be a problem on any cruising boat as these are very typical conditions.

[robert sailor]

[QUOTE=mikereed100;2263895]True, but is should not be a problem on any cruising boat as these are very typical conditions.[/QUOT

Totally agree with you.

[Polux]

Originally Posted by mikereed100

We have a hard and fast rule aboard that when we are sailing in the lee of mountains and headlands we are deeply reefed and have our small jib up. Our static stability with this configuration is 51 knots. Sure, it makes us slower, but we are cruisers, not white knuckle sailors. On the other hand, I would happily sail fully canvassed on your boat in those conditions. I'll bring the beer and Cheeze Whiz.

My respect for you grew bigger It is not about white knuckle sailors it is about liking as much to sail as to cruise and enjoy sailing. I found out that many cruisers don't enjoy as much sailing as cruising, some see sailing just as a mean to an end: cruising.

Nothing wrong about that, but performance boats are made for the ones that like sailing and let me clarify my position here: I do like sailing and I do like performance cats much more than condo cats. I could easily have one (never a condo cat) but does not invalidate what I said and capsize number shows that for sailing a performance cat, specially if it is not a big one, a much more careful approach has to be taken if the boat is not been sailed actively by a crew, but just cruised by a couple.

I am not sure that I would be the type of guy to be able to do that, after all accidents like the ones that capsize a performance cat are pretty rare and one tends to forget that they can happen to oneself.

[44'cruisingcat]

Originally Posted by robert sailor

You may be right as to the wind power but Polux speaks the truth. Having the wind gust from 20 to 25 on a cruising mono hull is no big deal and very easy to deal with even if well over canvased.

No big deal on our boat either. We've had it go from 10 knots to 38 knots under full sail. Never lifted a hull, but it certainly got my attention.