Catamaran Sinking

[socaldmax]

Perhaps there are a lot of foam blocks included in the construction.

[Palarran]

Originally Posted by 44'cruisingcat

To be honest I doubt that your boat would actually sink. While it's much heavier than mine, I still think there would be enough coring and sealed chambers to keep it afloat.

My generators alone weight over 1600 lbs. Add a dive compressor and gear to that and so much more it's ridiculous it is much better to go under the assumption the boat will sink.

IMO, with cats, truly watertight bulkheads are your main, and for many, only protection to sinking. Even if a boat were to float partially submerged, the end result will probably be the same. In the case here, where a escape hatch blows open, that didn't happen in calm water. In a gale or storm, the wave force on a half sunk and disabled cat is going to finish the job off sooner or later.

Bulkheads, lots of bilge pumps, and constant power to run them is what provides me peace of mind when I'm 800 miles off shore.

[44'cruisingcat]

Originally Posted by donradcliffe

I'm now a little curious about the material volume. I just did a rough calculation, figuring that your boat hulls are 12 meters long, 2 meters high, roughly v-shaped. If I add 50% for the bridge structure/decking and assume one inch thick cored construction, I get about 3.6 cu meters, which would float 3.6 tonnes when awash.

This would explain why some cats are close to sinking, but others seem to float fairly high when holed.

If you put 8.6 cu meters into a 4 ton shell, it should float about half out of water when both hulls are holed. But does it really average over 2 inches thick, or are my estimates off??

I'd suggest your estimates are a long way off. For a start it's 13.5 metres long, the hulls are not V shaped, the deck cabin and bridgedeck consumed much more material than the hulls did, and there are at least 10 full or partial width bulkheads....

I guess if you've never built a boat you'd have no idea just how much material goes into one. Certainly just looking at one gives you no idea. At times it almost feels like you're putting materials into a bottomless pit.

[monte]

My volume guestimate would be
hulls 13.5m x 9m average circumference including deck
bridgedeck 6 x 6
floor 6 x 6
cockpit 4 x 6
bimini 3 x 6
bulkheads av 3 x 2 x 10ea
furniture 10 units x 2 x 2
all at 20mm thickness = 9.something m3, the rest would be offcuts/waste..20%
of course you could sink it in a swimming pool to see how much water it actually displaces...

[malbert73]

2 years back, my marina underestimated the weight of a 35 foot powerboat by 5 tons and tried to use the forklift to bring it up the hill. The forklift tipped over and dropped the boat. Because it was nearly new, insurance adjusters hemmed and hawed and finally didn't declare it a a total loss. So the guy was stuck with a heavily damaged boat needing extensive glass and bulkhead repair which took over 1 year. The next guy to get hauled told the marina "if you ever drop my boat, pick it up and drop it again until it's in pieces."

Sort of how I sometimes feel about the sink vs float argument. If I sustain enough damage to swamp my hull- I don't think it matters as much whether I sink or float in swamped condition. Either will be near total loss hull and systems/interior damage, and if I'm insured maybe better if boat sinks? Also in the conditions in which you would hope to use the swamped cat as a lifeboat are half filled hulls are stable enough to rely on in lieu of liferaft?


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[amphibious1]

Aloha all

Not to pick sides as far as catamaran sinking. Obviously some will float and some will sink. There are lots of factors in the equation. But as a 39 Privilege owner this article from Dave on Exit only does bring some peace of mind. Also going back to original point of thread. The 39 Privilege has the "escape" hatch in the bridge deck so even if it fails its not as dramatic. I feel it is a better design as far as keeping water out. Hope I never find out if it is a better design as far as climbing out of it.

This is a great read and cool pictures.

http://www.maxingout.com/captainslogarchive38.htm

[Emmalina]

Here's one on the beach in Thailand.. It was a bare boat charter....
2nd one this year....
Dragged at anchor till the beach could smash the saildrives out and sink it
They are waiting till the swell subsides to go collect the debris

[barnakiel]

This much damage from beaching?

But I read on CF that one of the huge advantages of a cat is that you can beach yours!

Strange.

b.

[Sand crab]

You only beach in a calm area. Cats aren't made to be repeatedly slammed into the bottom. And some cats aren't made to be beached at all.

[Southern Star]

That Lagoon didn't end up like that because it was beached and obviously, a great deal more happened to it than knocking out the saildrives! Anyway, cat or mono, all that picture proves is that when a fiberglass boat takes enough of a beating on shore, it is apt to break up. Quel suprise!

[Cheechako]

Originally Posted by Jim Cate

As it was secured to a mooring at the time, I believe that it went sideways... ie, a "normal" capsize. Post flipping, it dragged the mooring through the mooring field, striking and damaging several other boats. Sad for everyone involved.

Boats involved claimed that there were gusts to around 80 knots, sustained winds between 50 and 60. There was a lot of shore damage... roofs blown off, trees down, and one poor chap was killed in his car when a tree fell onto him. The Bruny island ferry (a biggish car ferry) was unable to operate and took refuge behind a nearby point. The storm was embedded in a well predicted cold front, and was only this intense over a fairly small path. We were about 75 miles west (in Port Davey) and only experienced 55 knots sustained, no thunderstorm activity when the front passed over us.

Cheers,

Jim

I think we need to discuss just what type of car this was... and whether it was unsinkable or not!

[44'cruisingcat]

Originally Posted by barnakiel

This much damage from beaching?

But I read on CF that one of the huge advantages of a cat is that you can beach yours!

Strange.

b.

We beach ours probably about 10 weeks per year. And yeah, damage like that happens every single time. Did I forget to mention that?

[Emmalina]

Originally Posted by Southern Star

That Lagoon didn't end up like that because it was beached and obviously, a great deal more happened to it than knocking out the saildrives! Anyway, cat or mono, all that picture proves is that when a fiberglass boat takes enough of a beating on shore, it is apt to break up. Quel suprise!

Beached by a 25kn wind and a 2 day pounding by 2m waves !!
I think the requirements for bare boat charter in Thailand are ... A pulse

[captlloyd]

I don’t have a cat but want one. I always thought that in lue of an escape hatch a battery powered drill with a battery powered sawsall would be a much better idea. Kept in the cabin, cut your own damn escape hatch !

[Caribsailor]

After hurricane Luis in 1995, there was a Norseman 400 that floated upside down with a walk-through hole in her hull for over a month. The engines were hanging out of the water and undamaged. She was salvaged and after repaired to both bows, etc. sold for $75,000. Cats are hard to sink...