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Old 28-11-2009, 10:21   #1
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Where to Get Foam to Make Boat Unsinkable

I am interested in making my boat unsinkable, so incase it gets punctured I wont sink and can hopefully repair the leak (underwater epoxy) then bail out and keep going. , I calculated I need 100 cubic feet of flotation.

I took some measurements, and I found I have space for 45 cubic feet under the bunks, I have not counted underneath the cockpit which I imagine has another 45 cubic feet. I am close enough that I may just have to put additional flotation higher up to reach enough.

I can also throw 500lbs overboard in this event if needed. Some additional flotation may be in the form of 5 gallon buckets or other sealed containers which can be used for other purposes normally.

I am wondering where I can get the foam to do this. I am not sure what to look for, but something that sprays in place would be nice, but I wouldn't mind cutting blocks to fit if I had to.

I appreciate any comments or insights into this task, Thanks.
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Old 28-11-2009, 10:28   #2
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Here ya go
Pour Foam, liquid 2 part, flotation, insulation
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Old 28-11-2009, 10:47   #3
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If you fill all that space with foam, where are you going to store all that stuff you'd need if you are planning a cruising life? Perhaps you're not and I've misread your post.

P.
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Old 28-11-2009, 18:51   #4
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Foam has a buoyancy of around 55 pounds per cubic foot. Unless your displacement is very light, it will take a lot of foam which will eat up a lot of stowage.
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Old 28-11-2009, 20:36   #5
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Well, the boat is a bristol 27. So you are right it will take a lot of foam to give it enough flotation. What is the alternative? A decent liferaft would take up a fair bit of space (although much much less) and costs more than foam. I guess I could do without either and hope I don't have any probems.

The expanding foam is interesting, but it would cost $2000 to get enough. I think I will try to find a source of free styrofoam blocks to use as filler, and hopefully only need a little bit of expanding foam around the edges, and in areas that are odd shapes.
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Old 28-11-2009, 21:09   #6
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I have had 2 boats that were unsinkable,one was/is a 24ft ULDB which i designed and built ,launched in 1987.You really only need to provide floatation for that which has negative bouyancy,in my case the hull is 1/2"foam with only 1 layer of 12oz biax on each side,decks etc all ply/foam/glass,basically i had to float the keel bulb,rig,outboard motor,deck hardware etc.I used pour foam under the vee berth and the afterberth under the cockpit,i dont remember the volume but its way more than needed and it has the added benefit of providing a lot of support to the hull and you never have to worry about where slings go.
The other boat was a Macgregor 36 catamaran which used blocks of styrofoam which i have a lot more faith in as it will never absorb water, which the pour in closed cell bouyancy foam will if the skin that forms on the surface as it cures gets damaged.Both of these boats are very light,with your boat you have a lot of solid glass to float,there is very little that already has positive bouyancy,really just the interior wood and deck core.
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Old 28-11-2009, 21:42   #7
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How do you know it was way more than needed? Were you able to test it? I imagine it is better to put too much than not enough. This is partly because you don't want to just not sink, but hopefully it is still possible to sail the boat with holes in it. I am thinking for this reason, the flotation should be as low as possible.

I read that solid fiberglass does sink, but since it is not as dense as steel or lead, it does not need as much flotation.
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Old 28-11-2009, 22:04   #8
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Quote:
Originally Posted by geckosenator View Post
I am interested in making my boat unsinkable, so incase it gets punctured I wont sink and can hopefully repair the leak (underwater epoxy) then bail out and keep going. , I calculated I need 100 cubic feet of flotation.
Quote:
Originally Posted by geckosenator View Post
A decent liferaft would take up a fair bit of space (although much much less) and costs more than foam. I guess I could do without either and hope I don't have any probems.
Quote:
Originally Posted by geckosenator View Post
I read that solid fiberglass does sink, but since it is not as dense as steel or lead, it does not need as much flotation.
The only boat that is "unsinkable" is the boat that is on the hard.

You really, *really* need to get grounded first with some good education and something to dilute this imaginary idea of carrying foam blocks to prevent you from sinking while you patch a hull underwater, and using that as an alternative to a proper life raft, should there be an emergency of some sort. How much money are you willing to spend to save your life?

If you do none of the above, and hit the water, let's hope that Darwin takes the day off, and please, don't take anyone on your boat with you.
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Old 29-11-2009, 08:06   #9
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Originally Posted by geckosenator View Post
Well, the boat is a bristol 27. So you are right it will take a lot of foam to give it enough flotation. What is the alternative? A decent liferaft would take up a fair bit of space (although much much less) and costs more than foam. I guess I could do without either and hope I don't have any probems.

The expanding foam is interesting, but it would cost $2000 to get enough. I think I will try to find a source of free styrofoam blocks to use as filler, and hopefully only need a little bit of expanding foam around the edges, and in areas that are odd shapes.
Your B27 is much too heavy to make it unsinkable with foam unless you practically fill it with foam. You will not have any room for water, fuel, food, batteries, spares, etc. Even if you were to make her unsinkable, consider that scenario carefully, basically if she is capsized, the flotation inside her hull could prevent her from self righting; should she simply be holed and down flood, she will still be awash in water--your pitiful supplies of food would still be possibly ruined, your water supplies ruined, your electrical system ruined, your engine most likely inoperable (just flooding the starter with salt water will do that), she will be wallowing in the swells and you may not be able to effect repairs to a hole because of all the damn foam in the way. If you did have to abandon ship, your boat now becomes a hazard to navigation since she can't be scuttled.

If filling your boat with foam to make her unsinkable were the best practice, everyone sailing offshore would do it. In fact just the opposite: we take a life raft with us, or an unsinkable dinghy or both to deal with that remote possibility.

If you want an unsinkable sailboat, buy an Etap. You can't turn your Bristol into one.
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Old 29-11-2009, 08:46   #10
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Use a lot of mahogany in the interior instead. That should help
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Old 29-11-2009, 09:05   #11
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Gecko,I calculated everything that went into the build in terms of posative or negative bouyancy and then figured what volume i had available for foam and there was more than enough,the placement low down allows a sinking situation to be no more than a nusance,it should still sail while "sunk". We have never had to test the theory though.The Catamaran had been tested by the builders and there were plugs in the hull just above the waterline,1@ 1 1/2" in each hull wich would be removed to allow the boat to drain under the power of the bouyancy then you bail/pump out whats left.It is a very reassuring feeling to know that no matter what ,you will not sink.I should point out that all of the Macgregor line are unsinkable,even the Mac 65 keelboat and it was done with block foam,that said all of the boats i have mentioned were designed with this as one of the many design compromises one has to make with ALL designs,they are light,it is much harder to retrofit a heavy boat such as yours and may well be impractical,i believe the Pardys have Taleisen equipped with inflatable air bags but she is all wood which is of course bouyant,you just need to do the calculations for your particular boat,also remember that unsinkable doesnt protect you if you have a fire onboard.
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Old 29-11-2009, 09:07   #12
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I agree with all the above remarks, and offer the following only as a trial concept.
Air is lighter than foam. An airtight compartment offers more flotation than one filled with poured foam or chunks of styrofoam. If it has a watertight opening, it can store some of the stuff on the boat, provided: it isn't broached by the damage under consideration, the lid remains watertight, and the whole idea doesn't invite carrying more heavy stuff. If you can live with having to open twenty or so Dzus fasteners to get to that next box of crackers, and remember to close the whole thing while you are eating them, it might work. But making these modifications with be tedious and time consuming so say the least!
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Old 29-11-2009, 09:56   #13
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There are boats built that have that. The Hollman FD12 is one that comes to mind. This is planned for in the building stages. I am not sure that you could do this to a boat already built unless you eliminated all storage space aboard.
While I don't want to sound as harsh as some here, it really sounds like it is not a good idea.
There is or was a product that would inflate inside your boat in a emergency that could do something like want you want, but it was expensive and hard to install. Don't remember the name, but it was a inflatable bladder.
Personally I would rather stay with my boat than on a life raft, but having a raft is pretty important unless you don't go outside of the bay.
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Old 29-11-2009, 10:40   #14
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We have friends who's Tayana 52 "Clambake" was hit by a freighter in the middle of the night and sunk in 90 seconds.

They wrote a book about thier experience. It's a good and fun read.

Google "Unsinkable" by Dee Saunders.


My point is, in such a scenario, that doesn't give one much time to light off an air pump to fill a bladder.


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Old 29-11-2009, 15:09   #15
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In reply to "How much money are you willing to spend to save your life? " Well, not a lot. If I could get a liferaft for like $100-$200 (max) maybe I would consider it. Otherwise I would rather spend that to get flotation to pack in the boat. I think I am more likely to survive on a half sunk boat than in a liferaft.

For most people, it is not practical to make a heavy boat unsinkable, but for me it is a little different. I am currently not using _any_ of the storage space under the bunks. I calculated that this volume is enough (plus a lot under the cockpit) is what is required (100 cubic feet). All my stuff is above the bunks, and it is working ok. I have enough storage space for more stuff too, but it might get to the point where (heavy) stuff has to get dumped over to improve the situation. I just need to locate the floatation as low as possible.


I do not have any engine which saves a bit of weight, instead I can put foam there. My electrical is sealed and unlikely to fail even if underwater, nearly all of the wiring is quite high up.


I fail to see how the boat would not self right if it were punctured and floating with foam. If anything it would be more stable because the keel would be lower.

I really like the idea of using air/water tight containers. You can use them for storage and organization but also as flotation, it also protects things (like electronics or metals) from corrosion. Just need a good way to pack them low in the boat.
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