Atlantic 57 Catamaran Capsized

[Jim Cate]

Another point not yet mentioned in the capsize by wind alone discussion:

The hydro drag of the mast, rigging and especially sails (if set) is a large resistance to rotating beyond 90 deg heel. if we are talking about the effects of a very high speed gust, but one of limited duration, I think this resistance will enter into the equation.

Jim

[smj]

I talked to my father who has a Ph.D. In physics and was a professor of chemical engineering for 40 years specializing in fluid mechanics. He said he couldn't imagine the mono in flat seas going much beyond 90 degrees but would have to run the numbers, which at 85 years old he doesn't have the time for!


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[Moontide]

By the time the mast is in the water on a cat it would be past 90 degrees and you would be diving (climbing?) into a hull so your above water when the boat settles. There is so much beam I am a bit afraid to attempt a spreader dive for fear I wouldn't clear the side of the boat.

And in flat water I would think a mono couldn't go past 90, nothing to push it there. The problem is that when there is enough wind to get knocked down the water probably wouldn't be too flat, and there are untold stories of monos flipping, most come back up.

Then there are the single handed round the world race boats. Not sure of the exact numbers, but I seem to recall that the stability requirement is to be able to recover from something like 120 or 130 degrees. Those boats are so beamy that if the do go upside down they are unlikely to come back upright.

Doubt any cruising monohulls don't suffer from that and they will almost always come back up if turtled. Often with out any rig but upright. That assumes that the water ingress is not enough to sink it before it flips back up.

[Polux]

Originally Posted by Moontide

...

And in flat water I would think a mono couldn't go past 90, nothing to push it there. The problem is that when there is enough wind to get knocked down the water probably wouldn't be too flat, and there are untold stories of monos flipping, most come back up.

Then there are the single handed round the world race boats. Not sure of the exact numbers, but I seem to recall that the stability requirement is to be able to recover from something like 120 or 130 degrees. Those boats are so beamy that if the do go upside down they are unlikely to come back upright.

...

A common misconception about beamy boats. In fact those race boats you talk about had, by race rules, to prove they can re-right themselves in flat water.

https://www.youtube.com/watch?v=DxB68oMn8nE

[malbert73]

Originally Posted by Polux

A common misconception about beamy boats. In fact those race boats you talk about had, by race rules, to prove they can re-right themselves in flat water.

Correct but not fully generalizable to beamy stock cruisers with shorter cast iron keels that don't cant.

[44'cruisingcat]

Originally Posted by Polux

A common misconception about beamy boats. In fact those race boats you talk about had, by race rules, to prove they can re-right themselves in flat water.

No rig, and they use the canting keel to right them. A boat as beamy with a fixed keel and a mast would be a different story. There have been rescues from the Southern ocean from upturned racing mono's with keels still attached.

[Polux]

Originally Posted by 44'cruisingcat

No rig, and they use the canting keel to right them. A boat as beamy with a fixed keel and a mast would be a different story. There have been rescues from the Southern ocean from upturned racing mono's with keels still attached.

Regarding the canting keel effect they use it on these boats because they can and it would be stupid not to use it, but on other type of similarly beamy smaller ocean racing monohulls, that have not a canting keel, the rules also demand that they have to be able to re right themselves in flat water and they have to prove it.

https://www.youtube.com/watch?v=4gC1lPI_lJk

It seems that you also don't know that an Australian tank study published some years ago proved that on the conditions an offshore monohull can be capsized (with big breaking waves), a boat with the mast intact will re right himself faster than a boat that had lost the mast. It seems a bit odd but the tests and conclusions were quite clear (I read the full experience report).

Regarding boats of this type or in fact class A boats, to have remained inverted with the keel up, that only happened with boats designed till 20 years ago, that is also about the time RCD was fully implemented. Since then all existent IMOCA boats were modified to comply with the new rules and since then no more boats remained inverted with the Keel and bulb attached.

Since the boats have been modified in what regards final stability, 20 years ago, not a single of the more than 120 IMOCA that raced solo on the Vendee Globe have even being inverted (much less not being able than re righting themselves), without the lost of the keel or bulb and we see them keep racing at 16/20K on storms that would sink or would put almost any other sailboat sailing defensively or under a sea anchor or drogue.

[Lool]

It was dark

[danielamartindm]

Originally Posted by Seaslug Caravan

Thank you smj for the geography lesson. Yes we are well versed in world geography here in Aus.

Not only did the A 42 Capsize on a lake, but it did it in a sheltered bay on the said LAKE.

This from our very own CF search engine.


Registered User


Join Date: May 2006
Location: Great Lakes
Boat: Liberty 458
Posts: 22
Catamaran Capsizes on Little Traverse Bay
by Cliff Biddick

Tuesday, October 19th was much like a lot of others in the fall in Northern Michigan. The East wind blew up Lake Charlevoix creating a sea that gently, but relentlessly, rocked the tug “Heather B” when my cell phone rang.
Jeff Pulaski, the Service Manager of our Harbor Springs yard was on the other end. “Are you in the middle of anything?” he asked. After 35 years in the boatyard business, I have come to expect the unexpected on a regular basis. “We have a customer who has capsized his 42’ Atlantic catamaran in the middle of Little Traverse Bay,” he said. The Coast Guard has taken him and his two friends to shore and they are fine, but the boat is drifting, pushed by the East wind out of the bay. Can you help him?

.........

Why the catamaran capsized remains a mystery. The owner and his two companions had been sailing several hours in 15 to 18 knots of wind. They were inside the cabin with the boat on autopilot. In what can only be considered a 'microburst', it went over in less time than it took the owner to shut off the autopilot. He and the crew simply 'walked' up the wall and onto the ceiling where they remained dry for an hour and a half until the rescue divers from the Emmet County dive team arrived. The owner actually called the Coast Guard using his cell phone as his masthead antenna was 70’ under water.
__________________

Once again, crew inside cabin nice and snug.


Hope you have a nice day

A good point. And btw, who was maintaining a watch while everyone was below? A vessel under sail should always have someone on deck ready to ease sheets in the event of a heavy gust; and with flipping a possibility, engaging the autopilot and going below doesn't make a whole lot of sense on a catamaran in particular.

[smj]

Originally Posted by danielamartindm

A good point. And btw, who was maintaining a watch while everyone was below? A vessel under sail should always have someone on deck ready to ease sheets in the event of a heavy gust; and with flipping a possibility, engaging the autopilot and going below doesn't make a whole lot of sense on a catamaran in particular.

The autopilots on the Atlantic catamarans are "below" in the pilot house along with a steering wheel. I believe the sheets are in the forward cockpit, but I know of no one who would sit next to the sheets 24 hrs a day in 15-20 kts. Of wind. [emoji90]happens.

[Lool]

Originally Posted by danielamartindm

A good point. And btw, who was maintaining a watch while everyone was below? A vessel under sail should always have someone on deck ready to ease sheets in the event of a heavy gust; and with flipping a possibility, engaging the autopilot and going below doesn't make a whole lot of sense on a catamaran in particular.

Two of the crew were actively on watch having just reefed the staysail to the second reef point at the interior helm station. On an Atlantic 57 this is just inside the door to the forward cockpit. It takes two seconds to reach the mainsheet winch. The crew feel their lives were spared because they were inside. If anyone had been in the cockpit they likely would have been trapped underneath in the dark and possibly tangled in running rigging and sails. The "gust" was so sudden and intense no easing of the mainsheet would have prevented the capsize.

[double u]

(I can't help myself, I absolutely HAVE to write this
what would have been the consequence of this everyday occurence on a monohull???

[44'cruisingcat]

Everyday?

[Pete7]

Originally Posted by 44'cruisingcat

Everyday?

Hmm, a 42ft cat which is heavily reefed is blown over by a gust of wind, I also hope this isn't an everyday occurrence when sailing in the Great Lakes.

However, to answer the question, though I think Double U knows the answer, is the mono hull would be blown flat to 90 deg until the wind stopped unless the wash board are out and she takes on water.

Pete

[double u]

...I always considered squalls & gusts "everyday" occurences during our cruises...but again, this was anecdotal evidence & what do I know...
& "monos sunk by squalls"? this is exceedingly rare, I'd say!