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Old 22-12-2014, 08:27   #16
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Re: Capsized Atlantic 57 Salvaged

2-1 is actually the traditional design and is based on the likelyhood of capsize vs pitch pole.
- When you look at capsize, all the bouyancy is far from the centerline of the boat.
- When you look at pitchpole, only a small percentage is away from the center of the boat (hulls are fat in the middle and narrow at the ends).
- The result is to create enough righting moment, you need more length than width.

Modern trimarans are closer to square because the outer hulls are usually narrow with minimal bouyancy.
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Old 22-12-2014, 08:37   #17
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Re: Capsized Atlantic 57 Salvaged

FWIW- The G-32, a trailerable cat designed by Gougeon Brothers. Interesting approach to capsizing. I don't think more than about 15 were ever made.

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Old 22-12-2014, 08:43   #18
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Re: Capsized Atlantic 57 Salvaged

Iroquois catamarans were available at one point with masthead disc-shaped flotation to prevent a total capsize.

Wellington 44s (a monohull design) were available with positive floatation.
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Old 22-12-2014, 08:49   #19
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Re: Capsized Atlantic 57 Salvaged

Quote:
Originally Posted by colemj View Post
The A57 has a L/B of 2.03, which is for all intents 2. A L/B of 1.5 on a 57' boat would be a 38' beam. This would be closer to a trimaran number - way too square for a catamaran.

Mark
Or perhaps not, given that this rectangle ended up an inverted rectangle? I speak as a real novice, but as I understand it L/B ratio is one of the primary factors affecting multihull displacement along with SA/D. ~2 is, as I understand it, considered a 'bare minimum' in modern offshore cats.

Multihull Design Considerations for Seaworthiness

I've read the designer's article previously, and he seemed to concentrate on criticism of the crew and emphasis on how bad the squall was. For many of us, exteneded stretched of autopilot use are routine, and sometimes squalls just happen. The fact is that in a mono, this would have been a scary broach and maybe a shredded sail or two (yes, I went there ). And that's not really a criticism of multis as a whole (some of which I like a lot), but just a criticism of this particular multi and its ilk, which to my mind bring a bad name to the breed. That is to say, with critical dimensions chosen for inshore convenience rather than offshore performance - either too narrow, or both narrow and bloatedly top heavy. This is why tris appeal to me so much more than cats - more of them seem to look like proper sailing machines, beamy and lean.

But, as I say, I am a novice, and this post is really meant more as a question than a statement - why not have the extra beam, if it keeps you upright?

Oh, and as to what happened to Anna:

Large Cat Flipped off Niue
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Old 22-12-2014, 08:51   #20
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Re: Capsized Atlantic 57 Salvaged

Quote:
Originally Posted by robert sailor View Post
I would not worry about it, odds are you and I will die of something much more common that tearing a big hole in the hull and sinking. There are many yachts crossing oceans and while some have lost keels and others have broken up it is still a very rare thing to happen and I guess this is why it grips our imagination so much. Comparing the cruising lifestyle to most other things I have toyed with most of my life I think its a good bet that cruising is one of the safer things to do with ones time.
I'd like to agree with you but I can't. During an Atlantic crossing this past summer I had to alter course to avoid hitting a sunfish. I didn't see it until it was two waves ahead. Was probably 6'-7' in diameter and basking right at the surface. At night, forget it. I only learned after the fact that they can weigh up to a ton and that people have hit them and suffered serious damage as a result. Scared the crap out of me at the time, I didn't recognize it until we were right up on it.

Saw a lot of freakin whales on that trip and all kinds of garbage floating about, that's only going to get worse. I know someone delivering a racing boat that got run over by a trawler, couldn't see anyone in the wheelhouse.

Yeah, cruising is safe. But it's not without risks, sinking being one of them.
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Old 22-12-2014, 08:52   #21
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Re: Capsized Atlantic 57 Salvaged

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Originally Posted by a64pilot View Post
I've often wondered why an overload device isn't fitted to the main sheet?
Yes it could cause problems once you have lost control of the boom, and the boom could even be fatal, but it would be like an air bag in your car, that is the accidents happening, all your trying to do is lessen the blow. It should prevent capsize, extremely rare though as they are.
Likely another unreliable gizmo that inept skippers would come to rely on rather than being better skippers. Capsizes on typical cruising cats are so rare, and usually the result of being in weather and seas one shouldn't be in, that such a device is not necessary. Very light weight boats are another matter....

2 Hulls Dave
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Old 22-12-2014, 08:57   #22
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Re: Capsized Atlantic 57 Salvaged

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Originally Posted by Delancey View Post
I'd like to agree with you but I can't. During an Atlantic crossing this past summer I had to alter course to avoid hitting a sunfish. I didn't see it until it was two waves ahead. Was probably 6'-7' in diameter and basking right at the surface. At night, forget it. I only learned after the fact that they can weigh up to a ton and that people have hit them and suffered serious damage as a result. Scared the crap out of me at the time, I didn't recognize it until we were right up on it.

Saw a lot of freakin whales on that trip and all kinds of garbage floating about, that's only going to get worse. I know someone delivering a racing boat that got run over by a trawler, couldn't see anyone in the wheelhouse.

Yeah, cruising is safe. But it's not without risks, sinking being one of them.
I see a steelie in your future, Delancey...
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Old 22-12-2014, 08:58   #23
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Re: Capsized Atlantic 57 Salvaged

Here's a mono hull with positive buoyancy that is inverted and has a bunch of holes. Very sad. RIP to all sailors lost at sea.
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Old 22-12-2014, 09:29   #24
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Re: Capsized Atlantic 57 Salvaged

I don't really care about the multi vs mono debate. The G32, other than being ugly, had some great ideas. I like how they prevented inversion. Maybe I will incorporate that in my next super boat
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Old 22-12-2014, 09:38   #25
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Re: Capsized Atlantic 57 Salvaged

Back in the 70's? There was a beach cat, not Hobie, that had a Styrofoam ball at the top of the mast.
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Old 22-12-2014, 09:42   #26
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Re: Capsized Atlantic 57 Salvaged

A criminal act? Personally I think we have far to much legislation in our lives already and the choice of boats should be ours and not based on legislation. This is part of the satifaction of sailing - getting away from the red tape that strangles us. However, I agree that positive bouyancy should be a standard criteria as it is often easy to achieve on cats. The bows and sterns of my own cat have been filled with closed cell poured foam. It adds massive strength in the case of a collision as well as bouyancy as well reducing water ingress (I hope) as well as noise reduction. In the bows it also provides a platform to reduce the space available - making items accessible and reducing the likelihood of piling more 'essential' items in an area that should be kept light. There are some unsinkable mono-hulls (not sure how well these have been tested) - at the end of the day we all make our choices.
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Old 22-12-2014, 09:45   #27
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Re: Capsized Atlantic 57 Salvaged

Quote:
Originally Posted by europaflyer View Post
Or perhaps not, given that this rectangle ended up an inverted rectangle? I speak as a real novice, but as I understand it L/B ratio is one of the primary factors affecting multihull displacement along with SA/D. ~2 is, as I understand it, considered a 'bare minimum' in modern offshore cats.

Multihull Design Considerations for Seaworthiness

I've read the designer's article previously, and he seemed to concentrate on criticism of the crew and emphasis on how bad the squall was. For many of us, exteneded stretched of autopilot use are routine, and sometimes squalls just happen. The fact is that in a mono, this would have been a scary broach and maybe a shredded sail or two (yes, I went there ). And that's not really a criticism of multis as a whole (some of which I like a lot), but just a criticism of this particular multi and its ilk, which to my mind bring a bad name to the breed. That is to say, with critical dimensions chosen for inshore convenience rather than offshore performance - either too narrow, or both narrow and bloatedly top heavy. This is why tris appeal to me so much more than cats - more of them seem to look like proper sailing machines, beamy and lean.

But, as I say, I am a novice, and this post is really meant more as a question than a statement - why not have the extra beam, if it keeps you upright?

Oh, and as to what happened to Anna:

Large Cat Flipped off Niue
Capsizing sideways is one way of going over, and the wider the beam the better. However, pitchpole is a greater probability way of going over, and wide beam increases the chance of pitchpoling.

Your example of a 38' beam on a 57' boat would probably be a pitchpole machine.

As mentioned, 2:1 L/B is widely determined to be a design sweet spot for the above qualities - and the boat in question is designed this way.

Mark
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Old 22-12-2014, 10:32   #28
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Re: Capsized Atlantic 57 Salvaged

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Originally Posted by europaflyer View Post
I would say more that building a cruising cat with a length/beam ratio of >2 (like Anna) should be a criminal act. Not that I know anything really, but I would want to aim for L/B closer to 1.5 if I ever went a bit funny and wanted to buy a cat...
I checked and most of them have about the same ratio as that capsized one
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Old 22-12-2014, 10:35   #29
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Re: Capsized Atlantic 57 Salvaged

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Originally Posted by Delancey View Post
Yeah, criminal. We have so many stupid laws, at least positive buoyancy on multihulls makes sense and can usually be achieved without significantly impinging on living space or having a negative impact on performance given the fact that multihulls are by their nature compartmentalized.

Positive buoyancy on a lead mine monohull? Inverted, full of holes? You're smarter than that, at least I think you are. Or maybe not. Perhaps you would like to argue why they should be the same?
I agree that it is a lot easier on multihulls but some monohulls have a positive buoyancy unless they are really broke to pieces (for instance Pogo).
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Old 22-12-2014, 10:47   #30
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Re: Chris White on the capsize

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Originally Posted by jaybird1111 View Post
Mr White himself has made a statement and the article is quite good:

Chris White Designs
No news here. Chris white said that it was a wake up call but should not be since other big cats where capsized the same way by big unexpected huge gusts. Not frequent but unavoidable. I was once caught at night by a micro burst/tornado or whatever (It was dark) it was sudden, the winds were out of scale and the monohul I was sailed knocked down instantly, even if I had already no front sail and let lose almost instantly the third reefed main (the sail was ripped off from the mast) and the banner was shredded. Any cat that would have some sail out would probably have been capsized.

As I said, rare circumstances but not unknown.
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