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Old 19-11-2013, 04:50   #16
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Re: Unsinkable

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Originally Posted by maytrix View Post
Nothing is unsinkable. But some boats can be much harder to sink than others. As stated above, many cats will float upside down, but enough damage could get them to sink too.
SHould tell that to the slightly mad guy who tried to sink his Cat (John Gross Design called Eroica I think) and it just refused to go down no matter how many skin fittings he took off and how many holes he knocked in it, just sat there with about 50% extra draught and refused point blank to go down, and he did try very hard.

Anyway - this has been - like most things - done to death see THIS THREAD HERE
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Old 19-11-2013, 05:25   #17
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Re: Unsinkable

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Originally Posted by Factor View Post
SHould tell that to the slightly mad guy who tried to sink his Cat (John Gross Design called Eroica I think) and it just refused to go down no matter how many skin fittings he took off and how many holes he knocked in it, just sat there with about 50% extra draught and refused point blank to go down, and he did try very hard.

Anyway - this has been - like most things - done to death see THIS THREAD HERE
I like the bit in the other thread about how the Coasties have difficulty sinking abandoned catamarans with their deck guns. Wonder why a guy like Steven Callahan would turn out to be a multihull fan, maybe 76 days in a rubber raft gave him a different perspective?
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Old 19-11-2013, 05:33   #18
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Re: Unsinkable

I'm building my next boat out of shipping containers, they always seem to float. Now do I use one or two? That's the question.
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Old 19-11-2013, 05:38   #19
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I'm building my next boat out of shipping containers, they always seem to float. Now do I use one or two? That's the question.
Two, preferably with a consignment of BMW motorcycles inside , commonly found along the south coast of England

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Old 19-11-2013, 05:55   #20
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Re: Unsinkable

Quote:
Originally Posted by Factor View Post
SHould tell that to the slightly mad guy who tried to sink his Cat (John Gross Design called Eroica I think) and it just refused to go down no matter how many skin fittings he took off and how many holes he knocked in it, just sat there with about 50% extra draught and refused point blank to go down, and he did try very hard.

Anyway - this has been - like most things - done to death see THIS THREAD HERE
Good call Andrew, brought back some memories from the initial read but yes, it's been done to death and all the provisos have been clearly called.
Cheers,
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Old 19-11-2013, 06:35   #21
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Re: Unsinkable

The corred boats cannot sink. Your worst case senario is many tiny bits of boat floating around.

Assuming it's not a cored boat, the bottle idea has been suggested but if you run the numbers, it might help slow the sinking but is unlikely to squeeze enough in to stop it. Consider using light weight foaming. It comes in a couple of cans, when you mix it in the space, it expands and solidifies. It has a couple advantages:
- Fills the space completely. Bottle only displace maybe 50% of the space.
- If you do put a gash in the hull, the foam has a good chance of stopping water ingress. No water, no sinking.

I can't remember the brand but I believe there is a cored mono out there that is positively bouyant but I seem to recall it was expensive and came with some other drawbacks.
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Old 19-11-2013, 12:15   #22
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Re: Unsinkable

While I agree that cats generally should not sink, if they are rightway up, grp cats will normally float low in the water because most of the buoyancy is high up in the hulls and deck with the usual foam core above waterline and sandwich deck construction. If you want to be capable of organic recovery from hull damage leading to flooding, then you need enough buoyancy low down and adequately high watertight bulkheads to contain flooding to the damaged area and not inundate undamaged areas such as hopefully the engine bays.

So the jugs idea may work but it's not a given, it depends on the boat layout and location of the buoyancy. It would seem a sensible precaution before a major voyage to find out what the flooded waterlines will be for all conceivable damage situations and consider improvements if they seem inadequate. The designers should have such information but otherwise consult a naval architect, it's meat and drink to them. It would be a good idea to share such information on this forum.

Of course such cats float beautifully upside down, but the downside is that organic recovery is somewhat more problematical.
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Old 19-11-2013, 12:45   #23
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Re: Unsinkable

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Originally Posted by valhalla360 View Post
I can't remember the brand but I believe there is a cored mono out there that is positively bouyant but I seem to recall it was expensive and came with some other drawbacks.

One Brand was Etap. I believe the main disadvantage was that the skins were much thicker than normal, so interior space was reduced.
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Old 19-11-2013, 14:10   #24
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Re: Unsinkable

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Originally Posted by valhalla360 View Post
The corred boats cannot sink. Your worst case senario is many tiny bits of boat floating around.

SNIP
Most modern cats are designed to be very hard to sink. They usually have sacrificial bows, water proof compartments, no heavy hunk of metal underneath and are fairly light to begin with.

I was amused to see the comment about how a cat would sink if damaged by a 3inch deck gun. I suspect it would take more than one round to do it. In fact unless the attacking boat circled the cat and fired on both hulls even a three inch deck gun would not sink it. I also suspect if my cat was being attacked by a boat with a 3inch deck gun sinking would be the least of my worries.

Bottom line is even if it is possible to sink a cat it would be much harder to sink a cat than a monohull.
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Old 19-11-2013, 14:23   #25
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Re: Unsinkable

Apparently there is a European standard on what boats can legally claim to be "unsinkable". Trimarans come to mind, I know that Dragonfly and Neel trimarans are allowed to advertise their boats as unsinkable.
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Old 19-11-2013, 14:34   #26
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Re: Unsinkable

Arthur Piver, the "father" of modern trimarans, used to have a boat which he would deliberately chop holes in sacrificial panels (easy to repair afterwards) to demonstrate the capacity to continue sailing even though all three hulls were flooded. I don't know of any tri that sank. Well, there was one that got accidentally chopped up pretty badly by a Chilean naval ship attempting a rescue of the crew who had been dismasted. That was CRUSADER which was attempting to beat the New York to San Francisco clipper record. The portion of the hull that held the engine probably went down, but the rest of the hulls are probably washed up somewhere in the Southern Ocean.
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Old 19-11-2013, 14:59   #27
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Re: Unsinkable

Sinkable? Or not? Take a gander and decide:


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Old 19-11-2013, 15:14   #28
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Re: Unsinkable

I am reminded of this:

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Old 19-11-2013, 19:08   #29
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Re: Unsinkable

Anyway - this has been - like most things - done to death see THIS THREAD HERE[/QUOTE]


Thanks! Interesting read. Finding factory info on my Dean is next to impossible so if anyone knows where, it would be most appreciated.

I am liking finding areas that would nicely be foam filled. One could not miss, no mater what the damage or puncture. Perhaps having plastic bags and canisters of foam would be a great emergency measure to use if the worst happens? Filling the bags would be an easy option to remove after you get to dry dock. I am going to do some work in my engine compartments as I agree this would be the heaviest part of the boat.

I was living on a sink-a-board when it went down in the marina in the middle of the night and I am maybe a bit too cautious about this topic. I do think if it could easily (and cheaply) be accomplished, one would just be inviting disaster if it was not tended to. All I needed to do then is step out to the dock, not so easy to do in blue water.
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Old 19-11-2013, 19:37   #30
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Re: Unsinkable

Some of the contributions above make it pretty clear that you can flood or break up a hull that is of cored construction and it will still float, even if in pieces. So someone's bound to bring up the question of capsize.

In the end whether discussing sunk, flooded but floating, or capsized and floating, the comparison comes down to survivability for the crew. That comes down to 'exposure' and rescue chances.

The advantage of floating with your boat is:
1) easier to spot a 40ft boat that a life raft or swimmer
2) your food stores and supplies are nearby
3) possible shelter (depending)
4) possible self rescue (depending)

Either way I wouldn't want to be in that unhappy situation, but there is a certain comfort in knowing that my trimaran will float even if all three hulls were flooded. A very unlikely scenario, barring those 3-inch deck guns.
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