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44'cruisingcat · 17-02-2015, 19:34

Quote:

Originally Posted by a64pilot

I'm gonna replace my keel bolts with explosive bolts, so in case a sinking is imminent, I can just blow the bolts and be as un-sinkable as a Cat.
Soon as I find the bolts, I'll do it

Sent from my iPad using Cruisers Sailing Forum

If the rest of your boat is of cored construction, it could work.

mark_morwood · 18-02-2015, 06:39

This topic gets rehashed all the time.

Assuming its pieces are basically still attached to each other, any boat (monohull, catamaran, trimaran, ocean liner, ...) when flooded will sink (head for the bottom, rather than staying at the surface) if it weighs more than the weight of the water its pieces displace. There are examples of monohulls and catamarans in both categories. There just tend to be more catamarans in the floating category because of the widespread use of foam cored construction, and there tend to be more mono-hulls in the sinking category because they have a big dense weight on the bottom to help keep them upright regardless of their construction. However there are clearly catamarans that will sink if flooded, and mono-hulls that will float if flooded (Etap is one example).

You can move between categories by adding or removing sealed compartments, but they can be breached (or overflooded in the case of the Titanic).

Once you have a boat that floats when flooded, there is still the question of how usable is the space it provides? Some will float high enough for you to stay inside, some will float enough for you to stay on the deck (or underbody), and some will float not very usefully (see the picture above of a catamaran floating with just its bows exposed); but they are all still floating. Once again, this is very boat dependent.

So the argument is pretty silly as a catamaran versus mono-hull debate. It all really depends on the particular boat and how it is loaded.

MIRELOS · 18-02-2015, 07:28

the Titanic was "unsinkable"
life raft is worst scenario safety, but worst scenarios do happen

Scout 30 · 18-02-2015, 08:13

Explosive bolts might be extreme but the idea has merit. Why not some kind of quick, but not too quick, release system for the ballast?

**a64pilot** · 18-02-2015, 08:54

Quote:

Originally Posted by 44'cruisingcat

If the rest of your boat is of cored construction, it could work.

I was just teasing, my boat is a full keel, no bolts.
My personal nightmare is fire more than sinking. I figure in a sinking I will have at least some time, fire maybe not so much, plus I've been trapped under a tractor as a kid and burned pretty bad, so fire scares me.

There are advantages and disadvantages to everything, nothings perfect, just have to accept whatever the inherent weaknesses are in whatever it is you have and learn to deal with them, have a plan. For instance maybe a life raft is a more important item to have for a mono hull guy than a Cat owner?
For me and the fire thing, I want a way out that does not involve me having to go out over the engine as it may be what's on fire, and I will not block that hatch with a dinghy for crossings etc.

**s/v Beth** · 18-02-2015, 08:58

A ballasted monohull would be pretty unstable, exp in conditions which would sink a boat. If you don't believe me, try to take a Laser out in swells...
My question is still out there- do cruising cats not have separate chambers in each hull to keep it from sinking?

**a64pilot** · 18-02-2015, 08:58

Quote:

Originally Posted by Scout 30

Explosive bolts might be extreme but the idea has merit. Why not some kind of quick, but not too quick, release system for the ballast?

I believe the cure would be worse than the disease, likelihood of ever having to jettison the keel is so remote, to say nothing of how unstable the boat would become, plus maintenance and expenses of such a system.
Makes more sense I believe if that is a concern, sell what you have and buy something that is "unsinkable" or maybe a good life raft?

Cadence · 18-02-2015, 09:29

The whole thing seems like generalizations. What cat are we speaking of? What mono?

In each case it is the old apples and oranges argument.

Scout 30 · 18-02-2015, 09:33

Who crosses an ocean & isn't concerned about their boat sinking? 2 guys went out in their shrimp boat from our neighborhood a couple of days ago. They were so unconcerned about sinking that they only had one pfd. Only one of them lived.

I don't live in fear of my boat sinking but I take precautions. Of course releasing your ballast is a silly thought but so are inflatable bags in your boat or attaching a parachute to a plane.

2Hulls · 18-02-2015, 09:48

Quote:

Originally Posted by s/v Beth

My question is still out there- do cruising cats not have separate chambers in each hull to keep it from sinking?

My boat has "crash boxes" at the bows and sterns, both extending above the water line. I can't even get into the bow ones without cutting holes. There are opening drains, however, into the adjacent bilges to detect in-leakage into the void spaces.

These are primarily for protection of flooding the entire hulls in the event of a collision that breaches the hull below the water line, but for sure they would also help buoyancy if a breach occurs elsewhere.

Dave

mark_morwood · 18-02-2015, 10:04

Quote:

Originally Posted by s/v Beth

...
My question is still out there- do cruising cats not have separate chambers in each hull to keep it from sinking?

The question is as meaningless as the question: "Do cruising mono-hulls not have separate chambers in the hull to keep it from sinking?"

Some do, some don't. And just like mono-hulls some will float flooded just because of their construction materials and some will not, regardless of the presence of watertight bulkheads. Though rather more cats than mono-hulls will float when flooded because of the lack of a big lead weight.

There is no universal design for cruising catamarans just as there is no universal design for cruising mono-hulls. All boats have different strengths and weaknesses. For example I'd choose your boat (a Valiant 40) ahead of mine if I was heading offshore singlehanded or to high latitudes because I believe it is a design more forgiving of mistakes, particularly in survival conditions, but still performs well. We chose our boat a (Catana 48) for world cruising along the trade-wind routes with our family because of its strength, speed and space. But its all trade-offs that we each choose to make. For example - a smaller version of our boat circumnavigated via the great capes with I believe a short-handed crew; and friends of ours did a similar cruise to us with their kids in a Valiant 40. Both reasonable choices of boat that happen to be the opposite of the choice I would make.

**s/v Beth** · 18-02-2015, 10:57

Fair enough, I am appropriately chastened. I know tri's have a safety factor built in (where one hull can support the other two and I thought there was a design factor like that in cats. Thank you for your comments about Beth, she has been tolerant of me.

Cadence · 18-02-2015, 12:01

Quote:

Originally Posted by s/v Beth

Fair enough, I am appropriately chastened. I know tri's have a safety factor built in (where one hull can support the other two and I thought there was a design factor like that in cats. Thank you for your comments about Beth, she has been tolerant of me.

Newt,

It is also the center of gravity of a tri.. Granted pitch poling one you are in deep dodo the same as a cat just maybe a little harder to be stupid.

44'cruisingcat · 18-02-2015, 12:43

Quote:

Originally Posted by a64pilot

I was just teasing, my boat is a full keel, no bolts.
My personal nightmare is fire more than sinking. I figure in a sinking I will have at least some time, fire maybe not so much, plus I've been trapped under a tractor as a kid and burned pretty bad, so fire scares me.

There are advantages and disadvantages to everything, nothings perfect, just have to accept whatever the inherent weaknesses are in whatever it is you have and learn to deal with them, have a plan. For instance maybe a life raft is a more important item to have for a mono hull guy than a Cat owner?
For me and the fire thing, I want a way out that does not involve me having to go out over the engine as it may be what's on fire, and I will not block that hatch with a dinghy for crossings etc.

Yep, one thing I made certain of when I built my boat, was that there are two ways in and out of every berth. I've never been badly burned, (touch wood) but still the idea of getting trapped by fire doesn't appeal much.