Unsinkable

[Palarran]

As Factor noted, this subject has been discussed before. I would guess since I joined this forum it's been brought up about 15 times. It's always funny though to read peoples responses and rational.

My input is that if your worried about the boat sinking your focused on the wrong thing. I'd guess there at least 10 more likely catastrophes to worry about over sinking. Highly, highly unlikely. Loosing your rig, rudder, fire, collision, medical emergency, hurricane, reef, violent boardings - more likely.

BTW, I disagree with 44C in regards to "There's no excuse for building a cat that CAN sink". Many production cruising cats can sink after adding all the weight of "creature comforts". I'm fairly sure mine could as it's really heavy. But, it would also be very difficult to sink and would take quite a long time.

[nimblemotors]

Keeping expandable foam in liquid form on hand is not a bad idea!
I would not fill my bow compartment with it, makes it useless for anything else once that is done. As I said, using the containers to store fresh water gives them have triple duty, you can leave port with full water, as you use it up and get farther offshore, a little more safety there.

But note well, the bow compartment is not designed to keep the boat afloat, it is designed to prevent water getting into the rest of the hull if you smash into something.

[downunder]

Originally Posted by captainwireman

Anyway - this has been - like most things - done to death see THIS THREAD HERE

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.[/QUOTE]

From memory Dean did not use core material below waterline just GPRin many of his vessels so I expect it could need watertight compartments to float. Comes back to weight vs buoyancy again and volume of those compartments. Difficult without designers fiqures.

[downunder]

Originally Posted by Palarran

As Factor noted, this subject has been discussed before. I would guess since I joined this forum it's been brought up about 15 times. It's always funny though to read peoples responses and rational.

My input is that if your worried about the boat sinking your focused on the wrong thing. I'd guess there at least 10 more likely catastrophes to worry about over sinking. Highly, highly unlikely. Loosing your rig, rudder, fire, collision, medical emergency, hurricane, reef, violent boardings - more likely.

BTW, I disagree with 44C in regards to "There's no excuse for building a cat that CAN sink". Many production cruising cats can sink after adding all the weight of "creature comforts". I'm fairly sure mine could as it's really heavy. But, it would also be very difficult to sink and would take quite a long time.

I think 44C's point is that cats can be designed and built such that they can't sink. So me certainly could sink.

[Stumble]

Be careful of the foam in a can, and most expandable stuff. Most of it is open cell, so it will absorbe water pretty quickly.

[44'cruisingcat]

Originally Posted by downunder

I think 44C's point is that cats can be designed and built such that they can't sink. So me certainly could sink.

Yes. Can be and should be. It's also possible with keelboats, if more difficult due to their ballast requirements, but IMO all multihulls should be built so they can't sink.

[belizesailor]

Originally Posted by maytrix

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.

+1. I don't like the term "unsinkable". No boat is truly impossible to sink under any circumstances, but many multis could be a real challenge to sink.

Read a discussion of this by a notable multihill racer (forget who). He once hit a whale while surfing off the back of a big wave. His take was that many multihulls may not sink, but when you hit a whale at speed they can break into lots of small pieces (his case for carrying a life raft on a multi).

Reality is that some cruising cats can and so sink.

[rebel heart]

Just to add to the thread, here's 46' Leopard that sank.

http://www.cruisersforum.com/forums/...ion-99295.html

[Canibul]

Anytime I see someone say that something "Never" or "always" or "can't be made to" I pretty much start filtering the rest of their opinion.

[Rohan]

Originally Posted by rebel heart

Just to add to the thread, here's 46' Leopard that sank.

Actually, if you read further into that thread, the captain doesn't believe it actually sank. See here

[DotDun]

Originally Posted by 44'cruisingcat

Yes. Can be and should be. It's also possible with keelboats, if more difficult due to their ballast requirements, but IMO all multihulls should be built so they can't sink.

Please qualify. Can't sink due to a single problem or stay afloat with multiple problems?

Hence, if solid bulkheads are part of the 'can't sink' design and there are 2 failures, one on each side of the solid bulkhead, should it still float?

[rebel heart]

Originally Posted by Rohan

Actually, if you read further into that thread, the captain doesn't believe it actually sank. See here

Some more of the same captain's comments:

Originally Posted by virgincapt

In all these cases of a breached, cored hull, if the production process does not include vacuum bagging, then the interstices of the core are open and so will allow water to travel throughout the core, thus seriously altering flotation qualities of the foam. Thus a cat can surely sink.

[natew]

The Ady Gil comes to mind. Had it's front nose completely ripped off and was still afloat enough to be towed a fairly singificant distance back to the nearest port. Though I think the boat was made entirely of carbon fiber and weighed next to nothing and wasn't exactly your run of the mill cruising boat. However, you can see that despite losing the nose it was likely still well supported by the bouyancy of the amas which were intact still.

Also read somewhere that general cruising multis get their 'unsinkable' status from the displacement of the deck in the water. Apparently in many cases, even if the hulls are completely flooded the deck, once at water level, provides enough surface area to keep the boat "afloat" akin to a piece of paper floating in the bathtub.

[Cotemar]

Fountaine Pajot catamarans have blocks of crash foam in the bows.
Has a huge block of foam just behind the mast.
Large blocks of foam under the stern stateroom berths.
Most are foam core also. Just tons of flotation.

Here is a picture of one that floated across the Caribbean for months.

[downunder]

Originally Posted by DotDun

Please qualify. Can't sink due to a single problem or stay afloat with multiple problems?

Hence, if solid bulkheads are part of the 'can't sink' design and there are 2 failures, one on each side of the solid bulkhead, should it still float?

Stay afloat with multiple problems if built with sufficient buoyancy in the core materials to carry gross weight of the vessel.

Most of contempory cat designers use core materials in their bulkheads and many these days infuse them. Some of the older designs used ply bulkheads but even that will float.

http://www.multihulldesigns.com/pdf/hulls2lite.pdf