Unsinkable multihulls?

[Robin]

We were moored years ago by a Hirondelle cat that was struck by lightning which blew the echosounder transducer out of the hull, no other damage. It sank straight down and sat there on the bottom for several days before recovery.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Jacket]

So judging by the general trend of replys, its seems that those who state that all multihulls are unsinkable are wrong - most of the ones out there aren't.

Instead, it should be said that due to the lack of ballast its easier to make one unsinkable than it is to do the same to a monohull.

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[mirabriani]

Give it time.
Technology marches on.
Latest developments are monos with swing keels.
It may be possible to right a wide beamed mono.
The next step is to jettison the keel to lighten the yacht and give more time for the air bags to work. Hence self righting unsinkable mono
Hows that? I shall say "Told you so"

Regards Briani

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[snowleopard]

i've given this some thought and here's what i've come up with-

displacement 5.5 tons loaded.

crew & stores with neutral buoyancy: 1 ton
buoyancy of skin (sandwich construction) 3/4 ton
half empty water tanks 1/4 ton
ditto fuel 1/4 ton
holding tanks (kept empty at sea) 1/2 ton
bow crash tanks 2 tons

so if both hulls were holed she'd probably sink but if inverted it would only take a few cubic feet of trapped air to keep her afloat.


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[Ships_Cat]

I wonder how many cruising mono hulls have capsized and remained inverted. Seems to me that those that are single mindedly cat fans only quote race boats that have lost their keels or remain inverted because of ironing board type dimensions (eg the V60's).

Making fair comparisons one has to say there have been plenty of cat race boats that have come to grief, and to be even fairer I suspect a greater percentage of cruising cats have permanent inversion accidents than cruising mono's.

In fact I do not know of any cruising mono's that have stayed inverted or lost their keels (I suspect there have been some). Even with a relatively low AVR a cruising mono will uninvert as it is always wave action that is the primary cause of inversion and the same wave action will act to re-right such a vessel.

I have no overwhelming preference for either as I think they both have their place depending on the purpose. For here, assuming venturing beyond sheltered waters, I have to consider that a disproportionate number of losses and rescues from the southern non tropic Pacific seem to be cats.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[snowleopard]

<greater percentage of cruising cats have permanent inversion accidents than cruising mono's>

i recall being told that there had been no instances of criusing multihulls capsizing. since then there was an instance of a heavenly twins turning over in a force 10 off the hebrides and that odd one of an iroquois in the solent last year. apart from those, all the instances i know of have involved racing.

equally i know of no permanent inversions of cruising monos apart from the occasional keel falling off.

can anyone provide informed information on this?

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[BrendanS]

The logical people to ask would be the underwriters at a large marine insurance company, preferably one that provides cover globally. They would have such information at their fingertips, as this is one of the things they would base risk on.

<hr width=100% size=1>Me transmitte sursum, caledoni

 

[Ships_Cat]

<<<i recall being told that there had been no instances of criusing multihulls capsizing>>>

Although I think you may be mainly meaning cats, there have certainly been a number of capsized cruising multihulls - the best known around here being the Rose Noelle mentioned earlier in the thread, the crew living inside it until went aground off Auckland almost in the middle of civilisation (well if one could call Auckland civilised /forums/images/icons/smile.gif).

But I suspect that such accidents for both cruising monos and multi's are normally mainly with vessels with design faults or faulty management and not necessarily a natural fault of just being a mono or multi.

In the June 1994 Pacific storm which has been well documented, there were (from memory, I haven't got any of the books) 9 boats abandoned. One of those was a mono lost with its crew but I know that the vessel had a pre-existing structural problem for such voyages and I am told that the crew had a management problem. Of the other 8 vessels abandoned at least 2 were cats (one of which was run down by the rescuing vessel at the request of the cat's owners - I suspect that cat had a number of design and severe crew problems as well, as anyone who has seen the book "Heartlight" will probably also suspect). So a considerable number of cats and far more than the proportion of cats sailing that route would indicate.

Not long after that storm I was lucky enough to be with a professional skipper who was doing a yacht delivery and was caught in the same storm and was quite close to the yacht that was lost with its crew so in the same weather - although they were the closest they could not offer any assistance because of the weather, and added that from the radio sked's with shore it was obvious that the crew were falling apart. The interesting part was that this delivery skipper maintained that the storm was not really that bad and they managed quite well. There are also records of other cruising boats that were in the same area wondering why so many had been lost.

A good friend rescued the crew off a trimaran near Cape Horn some time back - another story.

So, obviously a lot more to what causes boats to be lost through being abandoned, sinkings or inversions than just whether they are a cat or not. In my view is a pity some are so strongly predjudiced one way or the other.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Birdseye]

I was carefull to say most MODERN cats would be unsinkable. Older designs like the Hirondelle and my old Prout were quite heavily constructed mostly from solid laminates rather than sandwich and either with fairly small or non existant crash tanks. But being rational about it, I cannot see how a modern multi can be less unsinkable than a Feeling (or is it Gibsea?) which has often been pictured floating full of water despite a keel hanging on the bottom.

I've no doubt at all that more capsized cats stay capsized than do capsized monos. After all, all capsized cats will stay that way whilst some monos will return to the upright. What state they will then be in is another question. And you also have to allow for the proportion that sink. And you have to allow for the fact that more monos will invert in the first place because it is easier to get them to do so.

As far as I could discover, there are no worthwhile stats one way or the other. The problem is that until pretty recently, there werent that many cats about. There still arent here in the UK, but there are lots in the US so we should soon get some hard data. In the meantime, my insurance on my cat was exactly the same rate that O would have had to pay on a mono according to the broker.

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[Richard_Woods]

The debate reached a similar point when we were deciding on the RCD stability standards. The Europeans had a big argument with the Americans. The US requirements are for sufficient buoyancy to keep the boat afloat, we wanted boats to be sufficently bouyant to support the weight of the crew as well.

So the question to ask is first:


How many monohulls have gone off shore and sunk taking the crew with them?
and second

How many multihulls have gone off shore, capsized but the crew been rescued?

Rose Noelle is just one of many incredible survival stories from capsized multihull sailors.
The problem with multihulls is that the crew come back to say what happened. No one knows what happens when most monohulls sink.

Having said that, there are a lot of multihulls around without sufficient bouyancy like the Catana range for example.

<hr width=100% size=1>Richard Woods of Woods Designs for quality sailing catamaran designs
www.sailingcatamarans.com

 

[Ships_Cat]

<<<The problem with multihulls is that the crew come back to say what happened>>>

I think you are stretching things a bit there Richard - many lost without trace. A long time back now but famously Arthur Piver in one of his own vessels. I recall another well known cat designer was also lost without trace in one of his own vessels 5 or so years ago (name escapes me at the moment).

And I concede monos disappear without trace too but they certainly are not alone in that.

For vessels of both types, fire is always a possibility for an unexplained loss as well.

Not making the point to decry cats, but making it to decry one sided arguments.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Richard_Woods]

Apologies, I should have said "tend to come back". Semantics doesn't reduce my argument however, which is that boats should bring the crew back alive.

Most assume that you only die when a multihull capsizes, or only die when a boat sinks. In 25 years I only know of one person who has died on one of my designs, and that was from seasickness.

And you are right about fire (I had a fire on a boat once when off Bermuda, fortunately we put it out). A guy in the marina here had a big fire on his boat last week, (the air conditioning unit caught alight). The boat is still afloat, but he was lucky to survive and he was tied to the dock so could get off.

A final thought, if Etap and before them Sadler can build successful unsinkable monohulls why aren't all monohulls made unsinkable?

and who in their right minds buys a boat that is unsinkable when they don't have to?

<hr width=100% size=1>Richard Woods of Woods Designs for quality sailing catamaran designs
www.sailingcatamarans.com

 

[mirabriani]

Blimey Chris!
Now you tell me

Regards Briani

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[ShipsWoofy]

Force 12 in a Twins

Lottie Warren the Heavenly Twins which sank off Shetland was reported to be out in a force 12. If you read the report by the skipper John passmore the boat was battered for around 48 hours before she went over. He then survived by hanging on to the inverted bridgedeck. The boat was found 72 hours after his rescue floating near an oil rig.

The report when you read in the comfort of the house sends chills down your spine. I am not saying a monohull would not survive, but for anyone to survive what John endured is pretty amazing. He talks about not being able to go on deck for fear of being blown over!

"Very carefully, slithering about the deck on my belly to reduce windage, I transferred the bow line to the port stern"

"I cannot say if things would have been different I had known the windshift was imminent. Certainly I imagined that when it came I would have half an hour before the difference in the pattern would be significant."

"Later the helicopter pilot was to tell me that windspeeds at this level, the wave pattern would change within five to ten minutes"

<font color=blue>"The estimate is that I was in the water - both in the hull and on top of it - for between two and three hours. When the Coastguard helicopter arrived, it took maybe another ten minutes to find a calm enough slot to come down below the 30m maximum wave height and get me off. That seemed like the longest time."</font color=blue>

The full account is here ><A target="_blank" HREF=http://www.topcatsail.co.uk>Woof

 

[Jacket]

This is the bit that surprised me. I'd always assumed that cats would have bouyancy - after all, if Etap are unsinkable, it must be easy to do with a keel-less multi. But judging by the photo's from Greneda, they're not.

And as Snowleopard's demonstrated, it would take very little bouyancy to make them unsinkable, so why aren't they? A sinkable multihull seems to be missing one of the main points in their favour, in these days of floating containers hidden in every wave (reportedly).

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[snowleopard]

protecting against disaster

enough buoyancy to make any boat insinkable takes up space. in a production boat this space has to be subtracted from the accommodation and space down below is one of the biggest factors in selling a boat.

the alternative is to take precautions against the most likely forms of disaster so reinforcing the decks against the risk of objects dropped from passing cranes would be a bit silly. on the other hand the risk of striking underwater objects is more realistic.

the main precautions taken by modern multihull designers include:

watertight bulkhead or crash tank to contain water in the event of a collision at the bows

escape hatches from all cabins in event of fire

escape hatch allowing access (in or out) below the bridgedeck in the event of a capsize

shear-off keels which will break off in the event of e.g. riding over a container, without leaving a big hole in the bottom

liferaft accessible when inverted.

an owner concerned about lack of buoyancy could always seal off a couple of cabins, add watertight doors etc. few do.

(feel any better brian?)

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[Sans Bateau]

It does amaze me that if people are so concerned about either multihulls or mono hulls being unsinkable why there is'nt a greater interest in ETAP's in the UK. Most ETAP owners would put the unsinkable feature of their boats as one of the reasons why they bought.

Whilst the thread is predominantly about multihulls, mono hulls have come into the discussion. A trully unsinkable yacht does exist, no if's but's or maybe's. If the owners of sinkable yachts were not concerned about, sinking, then magazine articles on liferafts would be far less interesting.

Look at that I covered two threads in one post!

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[Robin]

Does anyone know.....

............how many Etaps sank before they decided it was necessary to make them unsinkable?

One answer to your question is size, in two ways. Firstly size inside, which is reduced to incorporate the foam. Secondly size overall, I don't believe that it works on bigger boats, say 39/40ft and up?

I have to say in over 30 years of sailing sea going boats as opposed to dinghies, I have never once felt the need to have an unsinkable boat, but then I have never had a boat sink under me.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Sans Bateau]

Re: Does anyone know.....

To the best of my knowledge ETAP's have always been unsinkable. ETAP did have a 39ft boat up until recently, it is being replaced by a new 46ft boat which will be available soon.

On the subject of the amount of space lost to foam, space is lost, but the available space is used more wisely. Take a look at the storage space available in a Janneux 32 (current model), then take a look at the ETAP 32s. The Janneux may be 'bigger' in the saloon but there is no storage space, no lockers, just fiddles on small shelves, then take a look at the cockpit lockers, on the ETAP 32s they are cavernous, the Jan, you can hardly get a hank of rope in.

<I have never once felt the need to have an unsinkable boat, but then I have never had a boat sink under me.> Good, but it would seem from the thread that a lot of people ARE concerned about sinking!

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[Jacket]

I've always liked the concept of Etaps- having had a boat almost sink on me, the unsinkability aspect appeals. And they've got some other good design ideas. Its just that there stylings never particularly appealed to me (I guess I've got a somewhat conservative taste in boat styling).

But I'll still be giving them a close look when i'm buying my next boat.

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