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Old 24-06-2016, 11:41   #16
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Re: Boats That Stay Afloat

I've thought that a boat could be made unsinkable by fitting in the aft and forward cabins inflatable bladders that could be filled from bottled compressed air released by pulling an emergency handle. This would take less space than enough foam and could contain a self-sealing liquid to mend small tears.

I've no idea the volume required to overcome the weight of the boat and it may be another example of transitory exhilaration - the interval between the onset of a brilliant idea and the realization that it won't work.

Fair winds,

Leo
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Old 24-06-2016, 12:05   #17
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Re: Boats That Stay Afloat

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Originally Posted by Leo Ticheli View Post
I've thought that a boat could be made unsinkable by fitting in the aft and forward cabins inflatable bladders that could be filled from bottled compressed air released by pulling an emergency handle. This would take less space than enough foam and could contain a self-sealing liquid to mend small tears.
There was a commercial version (in the 80s ?) that used scuba tanks to inflate air bladders that normally were stored under the bunk cushions etc. Unfortunately, in a demonstration arranged for the boating press, the idea did not work and the boat sank anyway. If I remember correctly (and it is a long time ago) the bags damaged the hull/deck structure and broke away from the boat. Even a low pressure over a large area is a lot of force. Remember the airbag exhaust jacks that can lift the corner of car.

The company put on a brave face and declared the test a success anyway, but they went into bankruptcy shortly after.

It is an idea, unlike waterproof bulkheads, that can be retrofitted to existing boats. It deserves some further development. Staying with the boat rather than relying on a liferaft has a lot of advantages in most situations (fire is the notable exception). I have a feeling another company has produced a system more recently, but I have not seen it advertised for a while.
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Old 24-06-2016, 13:11   #18
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Re: Boats That Stay Afloat

Water is appx 62 lbs per cubic foot.
Salt water is a bit heavier, but go with the number for pure. (you can almost float a brick in the Dead Sea because of the high salt content)

So take the weight (in pounds) of the boat and everything on it and 200 lb per person CAPACITY... (this includes the flotation material)
multiply by 1.1 so the gunwales will stay above the water.
Divide that result by 60.
You have the volume of flotation needed in cubic feet.

ANY air bladder (inner tube, raft... whatever) is subject to holes... Therefore might be OK short term but I wouldn't count on it for extended support.

Of course, best is to keep the water on the outside of the hull.
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Old 24-06-2016, 14:12   #19
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Re: Boats That Stay Afloat

Having been sunk, Chucked up on the rocks in a violent storm,
I decided that I wanted an unsinkable boat,
My cat has four flotation chambers in it already, two in the front and two in the rear,
But I dont think thats enough for me, I single hand, So I would rather be on the top of the water than five miles below it, Even if it is just on the surface,
I intend putting blow up air bags under the beds at the back and one under the bed in the front,
It requires 37 cubic feet for every ton of boat, So three bags will suffice,
A cubic Metre for every ton of boat,
I dont lose any space as they are flat when not used, and under the mattresses, so you cant see them either,
They are blown up with air, and very quickly, I can use gas cylinders which are quite small, and can be kept any where close to the bags, or I can use an air pump,
Electric or manual,
Boats dont sink that fast unless you have a really big hole in it,
I can get them custom made here in any size I require,
If the boat is on the surface, I can wait out any storm, or other problem then fix the boat from the outside, then pump it out and head for the nearest beach to effect better repairs,
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Old 24-06-2016, 14:41   #20
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Re: Boats That Stay Afloat

[QUOTE=noelex 77;2151611]Sailing a small boat offshore is never going to be 100% safe.

Nor a big boat, even a very, very big one.

Maybe, with Brexit and all, I've missed some news, but at this point I do not even know how the two bodies found actually died. I think it is too early to blame even the father, despite preliminary information making it easy to do so. I can think of many scenarios that operate in many different directions, some without any real blame or finger pointing.

In any event, keeping in mind the vessel that provided her nickname and reputation, vessels that deserve the title "unsinkable" are at least as rare as the real Unsinkable Molly Brown. I know surfboards and windsurfers may be exceptions, so do not try to go there.
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Old 24-06-2016, 14:52   #21
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Re: Boats That Stay Afloat

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The most likely answer is that folks are not willing to pay the price and/or loose the storage space that is occupied by the flotation. In reality, not many yachts sink, and not so many people worry about t hat happening to them.

Jim
There are other alternatives. Instead of adding more flotation, you could reduce the weight of the boat.

How does everyone feel about quick-release keel bolts?
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Old 24-06-2016, 15:02   #22
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Re: Boats That Stay Afloat

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There are other alternatives. Instead of adding more flotation, you could reduce the weight of the boat.

How does everyone feel about quick-release keel bolts?
You'd have to blow the mast, then the keel if you don't want to be inverted.

The keel weight is there to keep you upright despite that heavy pole sticking up.

It would pretty much have to be explosive bolts (salt water maintenance nightmare) or a rather complicated mechanical system... or have the keel bolts run up tubes all the way level with the deck, where the quick release would be.
Otherwise... you'd be opening 2 (or more) keel bolt size holes to let water into the boat.

I could see it being done... I could also see it flipping the boat when the keel gets dropped before the mast.
Probably the tubes would be the solution... and 2 safeties (at least) to get past before dropping the keel weight.
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Old 24-06-2016, 15:10   #23
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Re: Boats That Stay Afloat

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I could see it being done... I could also see it flipping the boat when the keel gets dropped before the mast.
Probably the tubes would be the solution... and 2 safeties (at least) to get past before dropping the keel weight.
"Hey, Joe, what does this switch do?"
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Old 24-06-2016, 16:07   #24
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Re: Boats That Stay Afloat

More fundamental then "unsinkable" is simply a seaworthy vessel.
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Old 24-06-2016, 16:33   #25
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Re: Boats That Stay Afloat

Etap yes. Sadler potentially only.

Boats without ballast too (cats, tris) and also boats that can drop the keel in emergency.

b.
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