Unsinkable

[Factor]

Originally Posted by rebel heart

Some more of the same captain's comments:

Originally Posted by virgincapt View Post
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.

Maybe on that boat - but on a closed cell foam boat, please explain how the water will travel through the core

[Stumble]

Originally Posted by Factor

Maybe on that boat - but on a closed cell foam boat, please explain how the water will travel through the core

The captain is just wrong. Any foam suitable for use as core foam will provide positive buoyancy. While he is technically correct that foam, even closed cell foam, will over time absorb water, it is a very long process. Even a fully submerged boat would take years for it to matter much.

Think all the floating docks that use styrofoam blocks for flotation. They neither have nor need vacume bagging for water proofing.

[44'cruisingcat]

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?

A boat like mine simply CANNOT sink. There would be at least 10 - 12 cubic metres of material, not including airspaces, in a boat that cruises at around 6 tonnes. You could puncture or flood all of the 50+ sealed compartments, and the boat would still float.

It honestly baffles me that people can't grasp this concept. Archimedes understood it more than 2000 years ago.

To make it simple - If you Build a boat entirely of buoyant material, it's unsinkable. Makes sense?

Obviously our boats aren't built of entirely buoyant material, but if enough material is buoyant, to support that which isn't, the boat will still be unsinkable.

Because multihulls don't need ballast, the opportunity exists for them to be built so they are unsinkable. IMO builders should be taking this opportunity.

[44'cruisingcat]

Originally Posted by belizesailor

+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.

So if a boat was built entirely from Styrofoam, how would it sink?

[Rohan]

Originally Posted by 44'cruisingcat

So if a boat was built entirely from Styrofoam, how would it sink?

Tie a lead ballast to it, and it will sink.

[FlyingCloud1937]

Originally Posted by 44'cruisingcat

A boat like mine simply CANNOT sink. There would be at least 10 - 12 cubic metres of material, not including airspaces, in a boat that cruises at around 6 tonnes. You could puncture or flood all of the 50+ sealed compartments, and the boat would still float.

It honestly baffles me that people can't grasp this concept. Archimedes understood it more than 2000 years ago.

To make it simple - If you Build a boat entirely of buoyant material, it's unsinkable. Makes sense?

Obviously our boats aren't built of entirely buoyant material, but if enough material is buoyant, to support that which isn't, the boat will still be unsinkable.

Because multihulls don't need ballast, the opportunity exists for them to be built so they are unsinkable. IMO builders should be taking this opportunity.

So, basically you're saying. No need for structural Integrity, because the sum of the parts float anyways.

Some how I doubt your Theseus.

Lloyd

[FlyingCloud1937]

Originally Posted by Stumble

Think all the floating docks that use styrofoam blocks for flotation. They neither have nor need vacume bagging for water proofing.

Nor are they unsinkable, nor do they last, nor is unconcealed styro legal to build a float from in the US.

It degrades.

Many failures have proven the same.

?

[Dulcesuenos]

Originally Posted by FlyingCloud1937

Nor are they unsinkable, nor do they last, nor is unconcealed styro legal to build a float from in the US.

It degrades.

Many failures have proven the same.

?

No thats why now they encapsulate it in fiberglass, concrete etc,

[Dulcesuenos]

Our cat is unsinkable. My wifes shoes are positively buoyant and theres enough of them on board to keep a mono afloat.
I think they are the secret ingredient in boston whalers coring...

[Factor]

Originally Posted by FlyingCloud1937

So, basically you're saying. No need for structural Integrity, because the sum of the parts float anyways.

He aint saying that at all, where on earth did you get that from? Given his boat cruises very quickly and is his family's home I am pretty sure that structural integrity would be important. But seriously where did you draw that conclusion from?

[tamicatana]

factor,

you might as well ask why it is that leaner sailors come up into the multihull fora and tell us how our boats work. Happens all the time.

[DotDun]

Originally Posted by 44'cruisingcat

A boat like mine simply CANNOT sink. There would be at least 10 - 12 cubic metres of material, not including airspaces, in a boat that cruises at around 6 tonnes. You could puncture or flood all of the 50+ sealed compartments, and the boat would still float.

It honestly baffles me that people can't grasp this concept. Archimedes understood it more than 2000 years ago.

To make it simple - If you Build a boat entirely of buoyant material, it's unsinkable. Makes sense?

Obviously our boats aren't built of entirely buoyant material, but if enough material is buoyant, to support that which isn't, the boat will still be unsinkable.

Because multihulls don't need ballast, the opportunity exists for them to be built so they are unsinkable. IMO builders should be taking this opportunity.

Obviously, I didn't make my point.

Buoyancy will allow you to stay high and dry, but that shouldn't be the only requirement. Sitting on top of the bridge deck waiting for pickup is a nice feature, but intelligent design that allows the vessel to still make way with a single breach is on my priority list.

Solid bulkheads fore and aft of the engine(s). In my boat, the waterline is ~ the top of the oil pan, hence the engine will still operate with a passive leak inside the engine room.

Solid bulkheads ~8' aft of the bow, in addition to the typical crash box and foam storage, a secondary barrier to keep water out of the main living space.

Breakaway keels. A design for the keels that not only add 1000s of pounds of buoyancy via encapsulated foam, but breakaway in a hard crash.

More required than just foam. In fact, I'll take intelligent design first, foam core second as multiple catastrophic failures are far less likely than a single event.

[Jimbo485]

Hull material that floats. (Cored)

No lead. No keel. Daggerboards. (Or keels with a relate density less than one.)

Crash bulkheads fore, aft, port, starboard.

Fill it up with water and it still floats. Fill the crash bulkheads and it still floats.

Why is that hard to understand?

Try to sink a plastic coke bottle, make a conclusion and then extrapolate just a little!

[44'cruisingcat]

Originally Posted by Rohan

Tie a lead ballast to it, and it will sink.

And by definition, it wouldn't be made entirely from Styrofoam, would it?

[44'cruisingcat]

Originally Posted by FlyingCloud1937

So, basically you're saying. No need for structural Integrity, because the sum of the parts float anyways.

Some how I doubt your Theseus.

Lloyd

Getting close to the dumbest thing I've ever read. Exactly WHERE did I say there was no need for structural integrity?

I'm trying to explain, to those who like you seem to struggle with the concept, how a boat can be built such that it won't sink, regardless of how many holes it has in it.