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Old 23-12-2010, 22:12   #16
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On my other boat, SANTANA, I carried 3-12' weather balloons that were hooked up to a Scuba tank each.

We raised a 35' foot FRP sailboat off the bottom to the surface with the same setup. This rig was able to lift this boat high enough that the gunwales were above the surface enough so that when we repaired the hull, just tossed in a 2" pump and floated her all the way.

Santana was heavier, but figures indicated she would float enough to keep her ftom sinking. And she had a steel hull.

Doesn't really need a lot to keep a FRP boat afloat. Look at all the boats that sink at sea and later wash up on shore..
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Old 23-12-2010, 22:41   #17
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My poor brain is trying to come up with a reference to an article about retrofitting a cruising sailboat that was published in one of the major US sailing magazines or sites. I'm guessing it was about eight years ago.

I wouldn't mind if some cruising boat manufacturers would stop making cabin ceilings suited to professional basketball player heights - my wife is quite short - and would put foam in the overhead so as to give us some insulation as well as flotation.
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Old 23-12-2010, 23:16   #18
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Buy a multihull, they don't sink.
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Old 23-12-2010, 23:39   #19
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Flammablilty of expanding foam

Some expanding foams are highly flammable during installation and some even after curing. Some are fire resistant after curing so I assume you would want to use those types? In a notorious night club fire it was discovered that expanding foam had been applied to the walls of the club and this created the conditions for rapid spread of the fire and toxic fumes that lead to a very high cost in lives.
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Old 24-12-2010, 02:56   #20
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Many thanks for all the replies (paul youre a good man).

To those who've mentioned the cat, I agree completely, but crunching the numbers, for me personally, means an older 45-50 foot mono and reasonable spending money or 40ft cat and very restricted budget, cats just hold their money too well.

The insurance figures alone for extended off shore cruising tell me there is a fair element of risk 2-3 % of boat value is quite high, i know things are much different nowadays, epirbs, sat phones and the like, but its still a risk id like to minimize if i could.

To paul, i agree completely, proper and well thought through routing and weather is essential, lets face it , most typical distance cruisers would not have set sail in conditions like fastnet.

To others I agree, storage is a huge issue, but I am sure there are so many voids that you can't get access to in a modern mono that could easily have been foam filled in the factory for very little cost, some people have cited weight as an issue but a 2-3 cubic meters of foam has very little wieght.

I know most production manufacturers are just doing the cheapest as possible and pretty as possible for the average buyer who leaves the boat tied up most of the year and uses it very little, the type of buyer who is not concerned with possible disaster many miles from help. To me its such a shame that for so little cost and such a small amount of time it is not done as standard.

Lets face it , the only reason some cats are unsinkable is that european law says they must be so, cats made outside of europe are often sinkable.

Given the choice, I'm sure most of us would rather sail on an unsinkable boat!
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Old 24-12-2010, 03:43   #21
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When I was in La Paz, Two-Anchor-Annnie told me that her boat couldn't sink "because she had a lot of tupperware with the lids on tight."
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Old 24-12-2010, 04:14   #22
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The reason that most manufacturers dont do it , is that the numbers actually sinking are tiny compared to those afloat. Hence the risk doesn't justify the cost , leaving aside the technical issues. For comparison why doesn't your car have a complete fire automatic suppression system , why because the risk doesn't justify the cost and the punter would rathe spend the money on a better stereo .

Secondly merely keeping the boat afloat yet filled water is in itself not a very useful thing to do. A life-raft is a better solution. Unsinkable boats tend to pander to " perceived" fears ( often held by newbies) rather the real ones.

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Old 24-12-2010, 04:58   #23
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Dave,

I don't think is analogy of a car a good example as you can stop and get out onto land. Fire also is possibly the biggest threat at sea and offshore in any vessel uncontained means you would be in water.

To me the last place I want to be in the middle an ocean is in a liferaft and it is recomended you only get into one as your vessl sinks. I still prefer an unsinkable boat with the lifeboat in case of fire as last resort.
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Old 24-12-2010, 05:30   #24
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Quote:
Originally Posted by stevensuf View Post
I know 1 sqm = 1000kg buoyancy
I know 1 sqm =
More likely 1 cubic meter = 1000kg buoyancy…

Quote:
Originally Posted by chala View Post
foam is heavy and will ad to around 10% of the displacement
Filling the mast will ad weight.
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Old 24-12-2010, 05:35   #25
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When I was in La Paz, Two-Anchor-Annnie told me that her boat couldn't sink "because she had a lot of tupperware with the lids on tight."
This theory may not be too far fetched. I have heard someone who had waterproof bulkheads and then sealed every locker and cupboard. He'd calcualted that most storage areas even when full had at least 50% of the volume of the space was actually air. Galley cupboards more so. If you can seal all the doors and walls the he reckoned he had enough to keep the boat afloat. Sounds reasonable in theory.
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Old 24-12-2010, 05:49   #26
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Nice post! Like the idea of having weather balloons on board! Though I think watertight bulkheads make the most sense. You can not beat the insurance a life raft offers. We have a Portland Pudgy dinghy, which is similar to a huge watertight bleach bottle. It stows a sail in the gunnels, has a motor and is rowable. The idea being you could 'sail' to safer places. We just do coastal cruising so it works for us. Of course, you absolutely, positively MUST pay attention to the weather....not so much the forecasters, as to the moment.
Multihulls?....comfort, safety sure, but not my idea of 'sailing'
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Old 24-12-2010, 06:27   #27
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This is an idea I've been blowing hot and cold on for a while now with my little Corribee...
In reality most of the underberths etc 'storage space' is laughable as it akward shapes/sloped or fairly small and difficult to access short of re-arranging the boat to get at something... then put everything back so's you can move again... so I end up using the quarter berths instead..
Hull breach/floatation is one consideration but also insulation and muffling water noise on the hull...
I would be obliged if anyone could recommend a high density, fire retardent, non absorbant expanding foam thats easy to use and available on the European market... mainly Spain/Portugal to be precise....
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Old 24-12-2010, 08:17   #28
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Quote:
Originally Posted by stevensuf View Post
...
say a 45 foot 11,000kg yacht with say a 3500kg lead keel.

I know 1 sqm = 1000kg buoyancy with air
...
That gives you a rough starting point:
1 cubic meter=1000kg buoyancy
11,000kg yacht=11 cubic meters total to achieve neutral buoyancy.

To find out how much foam you'd need, you have to adjust the above volume for several variables. Subtracting for the natural buoyancy of the materials the boat is made of. Wood would be the biggest one. Add back for the materials with negative buoyancy (especially keel). Then add more for the weight of the foam (tiny), reserve for added cargo at times (a fair amount), reserve to make it float with positive buoyancy (quite a lot).

I bet as things balance out, the 11 cubic meters would not be far off. Say, +/- 2?

That's a cube over 3 meters per side. That's a lot of volume.

FWIW, my 1,300 lb (590kg) center console probably has over a cubic meter of foam between the hull and liner. 1-2" around the entire perimeter, under the fordeck storage, and under the floor except where the fuel tank is, at the stern, and some channels for cable routing. (I know, because running new cables for the VHF and depth sounder was a challenge).

Quote:
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...
To others I agree, storage is a huge issue, but I am sure there are so many voids that you can't get access to in a modern mono that could easily have been foam filled in the factory for very little cost, some people have cited weight as an issue but a 2-3 cubic meters of foam has very little weight.
...
IF you find a sailboat that has that much void space, you probably haven't found a boat suitable for cruising. On the huge majority of boats, they make use of every little space they can. You think you found a void, look in: Oh, that's where they hid the accumulator tank for the water system.

Unless my guessitamates above were horribly off (and they could be), you'd never find enough voids to float your boat.

But maybe you are not the type of person that uses every square inch of storage like some others? Maybe you can sacrifice that much space? Or maybe my estimates are severely flawed.

Disclaimer: I am no expert. Just thinking out loud.

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Old 24-12-2010, 16:51   #29
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Dave,

I don't think is analogy of a car a good example as you can stop and get out onto land. Fire also is possibly the biggest threat at sea and offshore in any vessel uncontained means you would be in water.

To me the last place I want to be in the middle an ocean is in a liferaft and it is recomended you only get into one as your vessl sinks. I still prefer an unsinkable boat with the lifeboat in case of fire as last resort.
The analogy was to due with comsumer preferences not really cars and fires. If you look at Etaps and teh unsinkable, they survive partially flooded, thats grand for coastal situations where help is at hand , but the boat is unlivable in offshore. Hence its better then useless.

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Old 24-12-2010, 17:02   #30
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Just remembered an article on retro for this subject..
Atom Voyages | In Search of the Unsinkable Boat by James Baldwin

Still think the best way would be to build with watertight doors through the various bulkheads. Large areas of air not dependent on each other.

The weather balloon solution sounds the simplest for no retrofit is needed. Where does one find them? Valve system? Expense?
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