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44'cruisingcat · 22-11-2013, 12:24

Quote:

Originally Posted by marvinmartian

The only reason it didn't sink was because it hit the bottom. She would have sank all the way if the capt. hadn't intentionally grounded her. The boat did not have enough positive buoyancy to remain afloat after the engine compartment flooded and then leaked into the adjacent compartments.

The story is quite clear on that as is the thread.

Cats can sink.

SOME cat's can sink. AFAIK nobody has ever disputed that. But some cat's can't sink. And that concept seems to be impossible for some people to grasp.

marvinmartian · 22-11-2013, 12:29

Quote:

Originally Posted by 44'cruisingcat

SOME cat's can sink. AFAIK nobody has ever disputed that. But some cat's can't sink. And that concept seems to be impossible for some people to grasp.

Perhaps, given certain conditions. But the manufacturers surely don't test them as such (eg., sink tests) and you have to take it somewhat on faith.

How can you be absolutely sure, assuming both your hulls flooded completely, that your cat won't go down? I know that might be a rare instance but it's good to think about.

Surprised the industry doesn't make balloons / air bags for this purpose. You could in theory inflate one or more in the respective compartments and always maintain positive buoyancy.

Jimbo485 · 22-11-2013, 12:42

Quote:

Originally Posted by markpierce

So, do ocean-going sailors on unsinkable boats bother carrying a life raft?

You are correct. We don't bother.

But fire could cause an issue!

44'cruisingcat · 22-11-2013, 12:49

Quote:

Originally Posted by marvinmartian

Perhaps, given certain conditions. But the manufacturers surely don't test them as such (eg., sink tests) and you have to take it somewhat on faith.

How can you be absolutely sure, assuming both your hulls flooded completely, that your cat won't go down? I know that might be a rare instance but it's good to think about.

I've already answered this several times. Having built my own boat, I know how much material went into it. The materials for the bare hull shell occupied nearly 9 cubic metres. Then more material went into the furniture etc. Totalling around 12 cubic metres.

At launch the boat weighed 4.8 tonnes. We cruise at around 6 tonnes.

In order to sink, the boat would have to displace around 12 tonnes of water.

markpierce · 22-11-2013, 14:55

This boat is unsinkable as long as it stays aground.

downunder · 22-11-2013, 16:09

Quote:

Originally Posted by markpierce

This boat is unsinkable as long as it stays aground.

Yes. That's the problem for most metal power vessels and monohull sailing vessels and why the best designs have enough watertight spaces/and crash pumps systems to manage hull breaches and to stay afloat as generally they do not have enough inbuilt buoyancy as that of a cored construction.

In Australia there are increasing numbers of power vessels being built by flat panel cored materials using similar methodology as 44C did with his vessel. Not only are they fast because of the low weight but they can also be built unsinkable.

**minaret** · 22-11-2013, 16:29

Quote:

Originally Posted by 44'cruisingcat

SOME cat's can sink. AFAIK nobody has ever disputed that. But some cat's can't sink. And that concept seems to be impossible for some people to grasp.

How about " some BOATS can sink, some can't"? It's not like positive floatation is a multihull exclusive. Plenty of monos out there which do the same thing, for what it's worth.

About Daydreamer

I almost bought this boat, based on amongst other things her positive floatation. Then after some research, I decided an almost sunk vessel with decks awash isn't worth much in a seaway, if anything, and I got some serious offshore life rafts and high quality hard dinghys as well as the boat I really wanted instead.

I'd guess the ratio of monos with PF to ones without is about the same as cats. That is, monos have Etap, Flying Dutchman, etc. etc. And multis have a lighter class which can't be heavily loaded with cruising gear and has PF as well. But most production cruising models loaded for cruising will sink, or mostly sink, just like heavier cruising monos will. Or close enough that its a moot point.

As an example, the Ranger 20, one of the most common US production sailboats of which thousands were built, designed way back in the sixties or seventies, featured PF.

http://www.sailingtexas.com/sranger20b.html

**minaret** · 22-11-2013, 16:49

Quote:

Originally Posted by marvinmartian

Surprised the industry doesn't make balloons / air bags for this purpose. You could in theory inflate one or more in the respective compartments and always maintain positive buoyancy.

There are a number of brands, but Holt Allen is the most common. They make buoyancy bags in a number of shapes and sizes, including mast bags for small boats.

APS - Buoyancy Bags

44'cruisingcat · 22-11-2013, 17:15

Quote:

Originally Posted by minaret

How about " some BOATS can sink, some can't"? It's not like positive floatation is a multihull exclusive. Plenty of monos out there which do the same thing, for what it's worth.

About Daydreamer

I almost bought this boat, based on amongst other things her positive floatation. Then after some research, I decided an almost sunk vessel with decks awash isn't worth much in a seaway, if anything, and I got some serious offshore life rafts and high quality hard dinghys as well as the boat I really wanted instead.

I'd guess the ratio of monos with PF to ones without is about the same as cats. That is, monos have Etap, Flying Dutchman, etc. etc. And multis have a lighter class which can't be heavily loaded with cruising gear and has PF as well. But most production cruising models loaded for cruising will sink, or mostly sink, just like heavier cruising monos will. Or close enough that its a moot point.

As an example, the Ranger 20, one of the most common US production sailboats of which thousands were built, designed way back in the sixties or seventies, featured PF.

Ranger 20 sailboat for sale, used sailboats

I was responding to a post which said "Cats can sink"

I disagree that the ratio of multi's and keelboats with PF would be even remotely similar. Keelboats have to provide several extra tonnes of floatation to compensate for their ballast. It can be done, but it's more difficult, so isn't done as often.

If you include ALL monohulls, including trailerboats, then yes.

Factor · 23-11-2013, 03:36

BTW - for those that love life rafts just remember that the biggest loss of life in a single "incident" in out part of the world was the 98 Sydney to Hobart with 6 deaths.

3 of those were 3 people in one life raft.

I dont negate rafts and dont reject them I just understand they are not a cure all.

gonesail · 23-11-2013, 04:21

Quote:

Originally Posted by rebel heart

There is a weird conception amongst some catamaran owners that if it "sinks" they'll just climb on top of their turtled craft, eat a sandwich, and wait for a chopper.

or hang out in one of the upside down hulls that isn't saturated with diesel hoping they can breath until the rescue boat comes along

Jimbo485 · 23-11-2013, 05:22

It has been done before.

Why the sarcasm?

Bit defensive?

C'mon, do some reading, see what has been done successfully before.

Then comment!

Jimbo485 · 23-11-2013, 05:25

No one sits on top. At least, not until rescue arrives.

They make themselves comfortable inside, tells stories, fish, eat, ****, drink, tell more stories, etcetera.

**minaret** · 23-11-2013, 09:10

Quote:

Originally Posted by Jimbo485

No one sits on top. At least, not until rescue arrives.

They make themselves comfortable inside, tells stories, fish, eat, ****, drink, tell more stories, etcetera.

Now that is truly hilarious!