Atlantic 57 Catamaran Capsized

[beiland]

Originally Posted by catsketcher

I love learning as much as I can but sometimes the internet can get me cranky. My blood pressure meds will be needed if I don't have a break for a while.
cheers for now
Phil

I think I am with you Phil

[malbert73]

Well here's a little firsthand and secondhand info to spruce things up after I waded thru these pages.
I was lucky enough to go for a sail/rig testing day sail on Leopard with my friend who's a pro captain and sailmaker a couple of years ago. What a great boat. Easily sailed at 11-13 knots in same true wind. Definitely high performance- you could feel the accel/decel instantly in puffs and lulls. Chris White was out on the boat as well and you can tell he's just a super guy who is really knowledgeable and passionate about his boats.
The layout actually is amazing. You can steer from inside just behind cockpit with great view if you want protection, but forward gives better view and sail control access than any other cat I've been on. Totally solves the peeking over a wall to steer or feeling like you're 20 feet up as most other cruising cats choose- both of which have merits but just don't appeal to me.
And yes, Leopard had very robust and easily accessed escape hatches in each hull. I must have spent 30 min just sitting in the hull watching water whoosh by the hatch at 12 knots [emoji3]

My friend is close with the captain of Leopard and they are all pretty certain this was a freak severe microburst/waterspout phenomenon. This friend used to captain a Swan 56 back and forth from med to caribbean to US and relays similar occurrence with a similar microburst/waterspout just north of Sardinia in the Swan- they were motoring with the main up (no Genoa) dead calm and then suddenly the mast tip was in the water to port - in two seconds - then upright and then bam mast in the water to starboard then upright again and back to dead calm. A bit of a mess below but were able to sail on.


I'd happily own and cruise an Atlantic cat or other performance multi. I think this extremely rare occurrence may be the one weather phenomenon where a mono may have an edge on a multi based on these accounts. Wouldn't be enough for me to pick mono/multi though- but enough to make me cautious in squally conditions... I own a mono but like politics I am an independent and am always frustrated by either/or arguments I read here on CF. neither mono or multi is perfect in all conditions and you have to pick what you want. Multis have a lot going for them. May be my next boat, but recognizing that a knockdown in a multi while much rarer than in a mono is possible and terminal

[Just Another Sa]

Originally Posted by Dockhead

Well, but it's not bollocks. I work with statistics.

The sample size reduces the confidence interval, but is certainly large enough for statistical significance. You can absolutely make conclusions about stability from this.

Does that mean that there is 0 chance that the Atlantic 57 has absolutely fine stability, and suffered two completely freak accidents out of 10 boats built, unrelated to any characteristics of the boat? Not zero! But very small indeed. Obviously if we had 100 boats or better 1000 boats, the confidence interval would be greater. But as Polux correctly stated -- this is pretty damning.


If I order one of these boats -- and this is just possible, as some possible changes in my life might lead me to gentler latitudes where the A57 could be the right boat for me -- I will certainly hire an independent NA to look into this very thoroughly, and work with Chris White to come up with possible design changes to reduce this risk.

Regarding this: "Does that mean that there is 0 chance that the Atlantic 57 has absolutely fine stability, and suffered two completely freak accidents out of 10 boats built, unrelated to any characteristics of the boat? Not zero! But very small indeed. "
the correct answer has nothing at all to do with statistics, and it is 100%.

I would expect a person working with statistics to know what conclusions can be drawn from statistics and what not, unfortunately you missed that basic fact.
2 boats in different conditions, one of them flipping over does not statistically prove that the flipped one had worse stability. Observe the same 1000 times and it still proves no such thing.
Even if the conditions were the same, it still wouldn't allow to draw such statistical conclusion, it could the the result of the crews, and simple statistical fact about capsizing can't be used to determine was it about the boat, the conditions or the crew or something else.

[Just Another Sa]

Originally Posted by Polux

That's because a bigger boat has more stability that on really big monohulls some opt for a smaller AVS (even if always bigger than 100º). It is considered than the risk to be rolled by a wave is much, much less.

But there is a big difference regarding a cat: A monohull cannot be capsized by wind alone while a cat can.

There is no reason why a monohull could not be capsized by wind alone. Even up to 180 degrees or more. Begin with wind on the bare mast and finish off with wind pressure on the hull. It just happens to be extremely rare event.
Either widspeeds of a hurricane, or same windpressure with much less windspeed but significantly more (10 X) density of the fluid, some water droplets in the air is all it takes, be it heavy rain or waterspout.

[Just Another Sa]

Originally Posted by robert sailor

Actually the way this newer Oyster was built was in fact a crappy build and it is inferior to a Beneteau.

Yes indeed, but that conclusion can not be made based on statistics alone, you need more info on the event for that conclusion which you now have.
Therefore the conclusion of misusing statistics still stands.

[neilpride]

Originally Posted by Just Another Sa

There is no reason why a monohull could not be capsized by wind alone. Even up to 180 degrees or more. Begin with wind on the bare mast and finish off with wind pressure on the hull. It just happens to be extremely rare event.
Either widspeeds of a hurricane, or same windpressure with much less windspeed but significantly more (10 X) density of the fluid, some water droplets in the air is all it takes, be it heavy rain or waterspout.

There is a factual or documented case of a mono rolled by wind alone around or is just another stirr in the pot??

[Polux]

Originally Posted by smj

I believe a structural miscalculation would be considered a design failure.

Yes of course but that is not the point since it is obvious a structural miscalculation that happens rarely, as an error and has been corrected on all other Oysters, including the existent similar ones.

The discussion is if fast modern big performance cruising cats have too much sail (regarding RM) to be considered as having an adequate safety margin as cruising sailboats.

That doubt arises due to multiple capsizes of that type of boats, representing a very significant proportion of boats capsized among the same model of boat built by some manufacturers.

If this is proven true, there would not be properly a design failure, since if those boats were racing boats, to be sailed only by very experienced racing teams that would have a permanent look out and would be always ready to react at the slightest danger signal, the problem would not exist. Besides racing implies always some extra danger that should be excluded from cruising.

What can exist is a non suitability of that sail area for that RM while the boat is designed as a performance cruising boat. That implies that those boats can be sailed with a small crew that can or cannot be experienced and that lack of suitability can represent a capsize danger not acceptable on a cruising boat, being it a performance one or not.

[Polux]

Originally Posted by Just Another Sa

There is no reason why a monohull could not be capsized by wind alone. Even up to 180 degrees or more. Begin with wind on the bare mast and finish off with wind pressure on the hull. It just happens to be extremely rare event.

Sorry, there seems to be some ambiguation on the word capsize. I am using it in a sense of a boat being turned turtle, meaning upside down. Some call a capsize to a situation of a boat with the mast on the water, some would call it a knock down, implying that the boat will rise after that. Regarding a class A monohull to be inverted by wind alone (180º) it never happened and it is not possible.

It was on the sense of a boat being inverted that I was saying that modern class A monohulls will not be capsized. On a case identical to the one that lead to the capsize (inversion) of that 57ft cat, even a small class A sailboat would not be inverted but just knocked down till the wind passes it over, coming up again after that.

As I have said I had already, I experienced that with a light 36ft boat, has well as some other member that posted here, and in both cases the boats had no problem to right itself up, a bit like that Clipper racer, even if in the case of the clipper the big area of sail they had has prevented it to raise almost instantaneously.

Yes, those phenomena are rare but not so rare as to not being experienced by several members or being recorded on movie. Those phenomena are not just watersprouts but Micro burst or huge gusts of wind, way out of the scale. Chris white said that they all could have capsized that Atlantic 57.

[Just Another Sa]

Originally Posted by neilpride

There is a factual or documented case of a mono rolled by wind alone around or is just another stirr in the pot??

Show me a factual or documented case of a mono being hit by a tornado or a microburst, and you have a case of a mono being inverted 180 degs or more.
Even monohulls obey the laws of physics. It's only a question how much windpressure is needed to do it, not if it can happen.

[SV DestinyAscen]

In conclusion...

People that won't consider catamarans won't consider catamarans.

Monohull zealots (yes I use the term intentionally) will cite added safety of righting - although needing rescue after rig damage, severe injuries or failing electrical due to knockdown/ingress of water isn't that great either. Catamaran zealots will say preference to float inverted vs sinking - although I'd rather avoid both by being conservative.

Finally - everyone else who is remotely balanced will learn yes don't sail against weather on a schedule (not surprising that delivery crews are responsible for many catamaran incidents - schedule and overconfidence).

Reefing for the gusts and not the averages is pretty straightforward. Monohull owners have to be more diligent about deck safety, stowage, keel health. Multihull owners worry about different things. In the end no one is forcing you sail on a boat - so leave the other guy alone.

[neilpride]

Originally Posted by Just Another Sa

Show me a factual or documented case of a mono being hit by a tornado or a microburst, and you have a case of a mono being inverted 180 degs or more.
Even monohulls obey the laws of physics. It's only a question how much windpressure is needed to do it, not if it can happen.

You pull the triger first , not me, there is a case of a mono inverted by a microthing or a tornado??

[Just Another Sa]

Originally Posted by Polux

Sorry, there seems to be some ambiguation on the word capsize. I am using it in a sense of a boat being turned turtle, meaning upside down. Some call a capsize to a situation of a boat with the mast on the water, some would call it a knock down, implying that the boat will rise after that.

It was on the sense of a boat being inverted that I was saying that modern class A monohulls will not be capsized. On a case identical to the one that lead to the capsize (inversion) of that 57ft cat, even a small class A sailboat would not be inverted but just knocked down till the wind passes it over, coming up again after that.

As I have said I had already, I experienced that with a light 36ft boat, has well as some other member that posted here, and in both cases the boats had no problem to right itself up, a bit like that Clipper racer, even if in the case of the clipper the big area of sail they had has prevented it to raise almost instantaneously.

Yes, those phenomena are rare but not so rare as to not being experienced by several members or being recorded on movie. Those phenomena are not just watersprouts but Micro burst or huge gusts of wind, way out of the scale. Chris white said that they all could have capsized that Atlantic 57.

Again, any monohull can be inverted 180 degrees by windpressure alone, and extremely few will right themselves without wave action from that. It is both easy enough to calculate and also easy to test in practice in a wind tunnel. The only difference with similar size multihulls in that issue is that the windpressure needed for it is typically higher for monohulls. ULDB with high CofG and wide beam is the worst kind, and can need less wind than a multi to invert 180 degs.
Compare with a different size and even that advantage of monohulls can disappear.

[Just Another Sa]

Originally Posted by neilpride

You pull the triger first , not me, there is a case of a mono inverted by a microthing or a tornado??

I don't care about example cases. I trust that the laws of physics apply to monohulls too, until proven wrong. And that is not going to happen.

[Polux]

Originally Posted by Just Another Sa

Show me a factual or documented case of a mono being hit by a tornado or a microburst, and you have a case of a mono being inverted 180 degs or more.
Even monohulls obey the laws of physics. It's only a question how much windpressure is needed to do it, not if it can happen.

Yes, you are right about laws of physics. Two members on this thread said that they were caught by microbursts and described their experiences and the way the boat was knocked down and come up after that.

Some posts back another captain was describing what happened to a a big Swan caught in a micro burst and you even have posted a video of monohull caught by a waterspout, being knocked down and raising after the wind becomes less strong.

It has nothing to do with the intensity. When the boat is knocked down it offers to the wind the rounded hull and a small surface. The boat at 90º is far away from the inversion point, that in most cruising boats happens only with more 25 to 35º of heel.

The boat at 90 º has still a considerable RM and is making a lot of force to right itself up. Very small rotating force will be provided by the wind on the rounded hull surface and the wind will just be moving the boat laterally.

The fact is that there are many examples of boats knocked down to 90º by the wind in weird metereological phenomena but there are no record of any being inverted. Of course I am talking about Class A boats, but then almost all boats out there on the Ocean are class A boats.

Anyway we are not discussing monohulls here.

[PhiSig1071]

Originally Posted by Polux

Anyway we are not discussing monohulls here.

Sure as **** could have fooled me......