Atlantic 57 Catamaran Capsized

[poiu]

It's so similar to the Gunboat 55 incident where that cat was dismasted only a few hundred miles further north last year, also in a tornado/waterspout type of event. This is the area of the Bermuda Triangle. I wonder if there is something going on here to connect it all together...

The crew apparently had no time to do anything as the wind came on so suddenly, but still it shouldn't happen that a cat flips over.

A good defence may be a system like the RightSideUp device. I saw one fitted on a 5X recently. It looked impressive. It should release the jib and let out a chunk of main in the event of a huge wind automatically.

I suspect such a device will not be enough to stop a 120kt wind flipping a light cat like this anyway so it may be best to fit a weak link as well to allow the rigging to fail and so to prevent a capsize. You could then motor or jury rig something together to get to shore.

All said, I wonder if it is possible to prevent a capsize of a light cat in such conditions. Imagine if it starts to heel such that one pontoon is out of the water and that 120kt wind gets underneath a windward hull, then it may well flip even if the rig had already failed. It's all a bit worrying really as I was looking at a cat like this as my next maybe boat.

[belizesailor]

Originally Posted by arsenelupiga

put my physics hat on....


we know that Lagoon 420 capsized on mooring in cat 5 cyclone in Whitsundays, assuming around 150 kn winds and some waves caused it.

My cat is nearly same weight as A 56, and A56 has ~ 2x larger surface area assuming 50% longer and 50% wider.

1.5*1.5 = 2.25

Same for proportion of bridgedeck tunnel which may play role in capsizing.

So, rough assumption 2x less force required to flip A56 than L 420 due to structure only. Force proportional with square of wind speed.

sqrt(2) ~ 1.41, therefore A56 capsize danger with no sails is roughly 150/1.41 = 106 kn.

comments welcome

Ive seen this refered to as "static capsize" wind speed. Some cat designs have it calculated.

Bridge decks can become wings at those kind of winds speeds too.

[arsenelupiga]

Originally Posted by poiu

It's so similar to the Gunboat 55 incident where that cat was dismasted only a few hundred miles further north last year, also in a tornado/waterspout type of event. This is the area of the Bermuda Triangle. I wonder if there is something going on here to connect it all together...

The crew apparently had no time to do anything as the wind came on so suddenly, but still it shouldn't happen that a cat flips over.

A good defence may be a system like the RightSideUp device. I saw one fitted on a 5X recently. It looked impressive. It should release the jib and let out a chunk of main in the event of a huge wind automatically.

I suspect such a device will not be enough to stop a 120kt wind flipping a light cat like this anyway so it may be best to fit a weak link as well to allow the rigging to fail and so to prevent a capsize. You could then motor or jury rig something together to get to shore.

All said, I wonder if it is possible to prevent a capsize of a light cat in such conditions. Imagine if it starts to heel such that one pontoon is out of the water and that 120kt wind gets underneath a windward hull, then it may well flip even if the rig had already failed. It's all a bit worrying really as I was looking at a cat like this as my next maybe boat.

protection would be less bridgedeck area more net area, like tris or racing multis, so wind cant catch boat underneath.

[belizesailor]

Originally Posted by Seaslug Caravan

Chris White has details on his Web Page.

See... https://www.chriswhitedesigns.com/leopard-capsize

A couple of paragraphs below. Nice to know that the speculation is not limited to CF
...

I dont see the kind of rampant speculation, and vilification of crew/boat, so unfortunately common on CF in Chris' write up (in all fairness its not been bad on this thread). While a water spout is a theory, I think its a good one. Would be interesting to hear more directly from the crew.

Not much you can do about a water spout. Even if you see it early, their movement is very erratic. Even if you got sails down, the wind speeds are in ranges that could still capsize a cat or knock down a mono (had a friend on a mono get knocked down by one at anchor).

In this case and other capsizes, the boats have floated and rescue has been available. Dont recall reading a single event that resulted in loss of life or even serious injury. Worst case would be a remote cold water capsize.

[robert sailor]

Wow, speculation runs at some all time highs in this thread and is now almost accepted as facts. While anything is possible very few of these speculative weather/winds is probable. High performance Cats have flipped in a variety of wind and weather conditions and few at the levels being speculated here.

[belizesailor]

Originally Posted by robert sailor

Wow, speculation runs at some all time highs in this thread and is now almost accepted as facts. While anything is possible very few of these speculative weather/winds is probable. High performance Cats have flipped in a variety of wind and weather conditions and few at the levels being speculated here.

Under the conditions why would a squall or water spout be improbable?

These are theories yes, but I havent seen the sort of rampant speculation taken as near fact so common on some CF threads...which I usually just unsubscribe to.

[Franziska]

Sidenote and its surely been discussed elsewhere.

Normal squalls can be observed on (normal non Doppler type) radar.

How about Microbursts or waterspouts?

[belizesailor]

Never thought to look at RADAR when near a spout...been too busy stadning there with my jaw dropped...but if its touched down the spray and moisture it has lifted should show.

[robert sailor]

Originally Posted by belizesailor

Under the conditions why would a squall or water spout be improbable?

These are theories yes, but I havent seen the sort of rampant speculation taken as near fact so common on some CF threads...which I usually just unsubscribe to.

Squalls are very common for sure, sailed thru hundreds over the years but while gusty ,wind speeds have never exceeded around 40-45 knots give or take but I have heard all sorts of exaggerated numbers. Water spouts, seen quite a few but never been hit by one which would be equal to the odds of winning the LOTO. Obviously the boat flipped, we know that but that's not all that uncommon for the high performance Cats in certain conditions and it sure isn't just hurricane force winds. I don't think this is even a concern for the average cruising cat owner as their boats are heavy, slow with very small rigs and low sail areas compared to the performance Cats. I know cruising Cats flip as well but this newer breed suggests it is highly unlikely.

[Polux]

Originally Posted by Franziska

Sidenote and its surely been discussed elsewhere.

Normal squalls can be observed on (normal non Doppler type) radar.

How about Microbursts or waterspouts?

On a clear night with good weather and good visibility most don't turn on the radar, specially on light fast boats that avoid the use of a generator (due to weight) and are on energy mode saving. They trust their eyes but I believe that if they were all inside dinning was because they had no motive to get suspicious about any sudden weather change.

Robert, waterspouts are not rare in some places and even if I had not been hit by one, at least directly, some few years ago I had to almost invert my course to avoid one. Scary, the thing keep changing direction as if someone was pointing it directly to us

[belizesailor]

Originally Posted by robert sailor

Squalls are very common for sure, sailed thru hundreds over the years but while gusty ,wind speeds have never exceeded around 40-45 knots give or take but I have heard all sorts of exaggerated numbers. Water spouts, seen quite a few but never been hit by one which would be equal to the odds of winning the LOTO. Obviously the boat flipped, we know that but that's not all that uncommon for the high performance Cats in certain conditions and it sure isn't just hurricane force winds. I don't think this is even a concern for the average cruising cat owner as their boats are heavy, slow with very small rigs and low sail areas compared to the performance Cats. I know cruising Cats flip as well but this newer breed suggests it is highly unlikely.

I agree its not a big concern for the typical cruising cat owner (Lagoon and similar), but of course a CW is a very different beast.

Ive been in one squall with gusts to 90 knots, confirmed by ships instruments and NOAA data. Another w gusts to 85, same confirmation. Both in Texas...really intense T storms there. And many in the 50-60 knot range per ships instruments...one I remember the display flashing 64 just before the anemometer parted company with the mast. On a mix of cruising cats and monos, never seriously concerned about knock down/capsize because we saw them coming, or knew probability was high, so were prepared. A couple on high performance tris (Corsairs)...much more worriesome, but very experienced crew aboard.

Watched a huge system on RADAR envelop us on a cruising cat once...we were in a little donught hole right in the middle of this beast of a system, all ready reefed deep (in that case striking all sail would not have been a bad idea either)...winds dropped to near zero...then BOOM...50 knots. We immediately turned and ran with it, bringing apparent wind down to 38 knots...very manageable. But again...we knew it was coming. Had it been an even bigger gust...who knows.

[Polux]

Originally Posted by SVNeko

So you think the mini keels contribute to a wind-induced capsize? Although I have some doubts about the effect in the real world, I understand the theory that boards up allows a cat to slide sideways on a wave impact. But with respect to being sailed over, even assuming every 5X has its boards up upon being hit with a big gust, I think the sideways movement and whatever relief that might allow from the force of the wind would be minimal.

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.

[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.

[robert sailor]

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.

Still speculation but at a level that is somewhat believable.

[robert sailor]

[QUOTE=belizesailor;2263047]I agree its not a big concern for the typical cruising cat owner (Lagoon and similar), but of course a CW is a very different beast.

Ive been in one squall with gusts to 90 knots, confirmed by ships instruments and NOAA data. Another w gusts to 85, same confirmation. Both in Texas...really intense T storms there. And many in the 50-60 knot range per ships instruments...one I remember the display flashing 64 just before the anemometer parted company with the mast. On a mix of cruising cats and monos, never seriously concerned about knock down/capsize because we saw them coming, or knew probability was high, so were prepared. A couple on high performance tris (Corsairs)...much more worriesome, but very experienced crew aboard.

Watched a huge system on RADAR envelop us on a cruising cat once...we were in a little donught hole right in the middle of this beast of a system, all ready reefed deep (in that case striking all sail would not have been a bad idea either)...winds dropped to near zero...then BOOM...50 knots. We immediately turned and ran with it, bringing apparent wind down to 38 knots...very manageable. But again...we knew it was coming. Had it been an even bigger gust...who knows.[/QUOTE

There are squalls and there are squalls with in bedded thunder storms. Thunderstorms do generate gusts higher than your typical squalls and should be avoided if possible at sea. The air rising inside a large thunderstorm pulls surrounding air at the surface and can generate very strong winds. You would have to be deaf,dumb and stupid not to be aware of these conditions at sea. Your approach of following the wind in a squall downwind is the same approach I use as it eventually turns you around and back on course and it's a safe way to deal with strong squalls at sea.