Making a Boat Unsinkable with Expanding Foam

[David M]

Beyond a certain size range, it makes no sense to try to make a boat unsinkable...unless its a submarine. Foam eats up too much valuable space.

Boats that can sink are the reason we have life rafts and lifeboats aboard boats over a certain size range, which take up far less volume than foam.

[n07900]

i am also looking to make my kingfisher 20 unsinkable. and i am struggling to find a foam, in slab form that is not highly inflamable, not highly toxic if it is burning, closed cell so it doesnt suck up water in the atmosphere, plus because i need 2 cubic meters the cost is an issue.

answer to original poster. there is a foam called plastizote that fits all spec other than price. for my 2 cubic meters it would cost £2000 approx, so it is out of the question.

i would appreciate if any knows of suitible foam in uk.
there is a guy called the "the simple sailor" who sails his coribee into artic waters, and he has made his coribee unsinkable with foam.

any advise would be apreciated..nick

[Captain Bill]

Originally Posted by n07900

i am also looking to make my kingfisher 20 unsinkable. and i am struggling to find a foam, in slab form that is not highly inflamable, not highly toxic if it is burning, closed cell so it doesnt suck up water in the atmosphere, plus because i need 2 cubic meters the cost is an issue.

I looked up the spec's on your boat. It only displaces 2600 Lbs. Two cubic meters of foam displaces 4400 Lbs. It would seem to me that if you got holed, only about half your foam would even get wet. If the foam is not submerged it adds nothing to your bouyancy. In a 20 foot boat two cubic meters would seem to occupy a great deal of your usable space. If you are absolutely set on a foam solution I would suggest you recalculate your requirements which should be way less than 2 cubic meters. Most so called unsinkable boats simply means that the boat will not submerge past a certain point, usually the deck when filled with water. As the boat submerges the weight above the normal water line is relieved by the weight of the displaced water. By the time you get to the deck level one needs lots less foam to displace enough water to prevent further submergence. I would use the weight of the ballast plus 1/2 the weight of the rest the boat to calculate my foam requirements. If it were my boat I would use somewhere around 1600 Lbs of displacement or only about 3/4 of a cubic meter. Also you want to keep the foam high in the boat, near he gunnels. If you put it in the bottom you could create a situation where the boat became more stable in an inverted position if flooded.

This of course is internet advice and may be worth only what you paid for it.

[delmarrey]

Originally Posted by n07900

i am also looking to make my kingfisher 20 unsinkable. and i am struggling to find a foam, in slab form that is not highly inflamable, not highly toxic if it is burning, closed cell so it doesnt suck up water in the atmosphere, plus because i need 2 cubic meters the cost is an issue.

answer to original poster. there is a foam called plastizote that fits all spec other than price. for my 2 cubic meters it would cost £2000 approx, so it is out of the question.

i would appreciate if any knows of suitible foam in uk.
there is a guy called the "the simple sailor" who sails his coribee into artic waters, and he has made his coribee unsinkable with foam.

any advise would be apreciated..nick

If the foam is in a water tight container, like a thick walled plastic bag, then one doesn't have to worry about moisture. And if I had a fire on that size of boat, I'd be getting off of there long before any of the foam ever caught fire.

Most boats sink aft end first so putting the foam in the aft end is usually best. Like up in the hollows around the cockpit.

[justwaiting]

They built an unsinkable boat, it was called the Titanic

Seriously, as stated by most of the responses to the OP to make a sail boat unsinkable would require the use of valuable storage space that may well render the boat unsuitable for any extended cruising. Also clearly stated in this as well as many other threads is that fact that in many (most?) cases the crew give out before the boat does. I would argue that the desire to have the boat stay afloat is one that has concerned most of us at one time or another, my take on the situation is that rather than look at a passive system that will keep the boat afloat on its own structural resources a more workable approach may be to use systems that will give the crew time. That is to say, time to think, act and or for help to arrive. Ask you self what are the types of events that are possible to cause a boat to sink. My assessment (2 cents) is a breach in the hull either from a failure of a through hull, a rudder failure (with certain designs) or by impacting a hard object. In the first situation the three most probable causes are: poor installation, lack of maintenance or some one leaving sea cock open followed by a well heeled tack. In the second situation consider maintenance and solutions to minimize the effect should it occur. In the case of an impact on the hull then consider how you would pump water out of the boat and ways in which you could reduce the ingress of water. Contingency planning, pumps and having materials on hand to effect emergency repairs would be approach that i would chose to take.

i have had a boat sink on me. Some F#$k drunk in a power boat ran over the top of me when i was rowing my tender to the shore!!!! Some things you can not plan for.

[boatman61]

My thinking was as theres a large area under my v-berth that goes above the waterline and can be made water tight.
I figured that if I stuffed it full of closed cell foam (pressure can expanding foam) should I get holed forward then the foam would restrict the amount of water ingress to a bucketful or two.... instead of a threatening X gallons in an empty space....
Am I being naive...??

[delmarrey]

Originally Posted by justwaiting

They built an unsinkable boat, it was called the Titanic

Seriously, as stated by most of the responses to the OP to make a sail boat unsinkable would require the use of valuable storage space that may well render the boat unsuitable for any extended cruising. Also clearly stated in this as well as many other threads is that fact that in many (most?) cases the crew give out before the boat does. I would argue that the desire to have the boat stay afloat is one that has concerned most of us at one time or another, my take on the situation is that rather than look at a passive system that will keep the boat afloat on its own structural resources a more workable approach may be to use systems that will give the crew time. That is to say, time to think, act and or for help to arrive. Ask you self what are the types of events that are possible to cause a boat to sink. My assessment (2 cents) is a breach in the hull either from a failure of a through hull, a rudder failure (with certain designs) or by impacting a hard object. In the first situation the three most probable causes are: poor installation, lack of maintenance or some one leaving sea cock open followed by a well heeled tack. In the second situation consider maintenance and solutions to minimize the effect should it occur. In the case of an impact on the hull then consider how you would pump water out of the boat and ways in which you could reduce the ingress of water. Contingency planning, pumps and having materials on hand to effect emergency repairs would be approach that i would chose to take.

i have had a boat sink on me. Some F#$k drunk in a power boat ran over the top of me when i was rowing my tender to the shore!!!! Some things you can not plan for.

Manufacturing laws now require floatation material in anything under 20'. >> http://files.dnr.state.mn.us/educati...atbuilders.pdf

[jzk]

Lots of ping pong balls?

[anotherT34C]

Doesn't seem like a bad idea to have floatation balloons under the V and setee cushions, linked to a scuba tank. Maybe a bit expensive for something that will almost certainly not be needed?

[minaret]

For those of you considering weather balloons, etc. you might do some research on boat salvage. I have worked for many years right next door to Divers Institute of Technology, so although I'm not a diver and have no salvage experience, I have watched them raise boats weekly for years. They seem to acquire all sorts of derelict vessels for this purpose. We have been hiring their students for boatyard cleanup help for many years as well, so I talk to these guys a lot. They use salvage bags to raise boats that are very similar to the weather balloon idea, but purpose built for the task. The biggest problem they always run into is that a boat is not designed to take pressure from the inside of the deck. This means that in many cases if you inflate enough balloon to give you the necessary buoyancy to raise the boat, you will just rip the deck off and leave the rest of the boat behind. Often they end up using balloons on either side of the hull connected by a strap that goes under the keel. A lot of rigging is involved. I guess all I'm trying to say is, if you want positive floatation, consider the forces involved for your floatation type and location and beef up the structure accordingly if necessary. Under the V-berth is probably not gonna do it, you'll just rip the top off unless you make sure it's strong enough. We are talking about thousands of pounds of force. I know some production monohulls have done a great job in this regard, the FD12 comes to mind...

[Ike]

i am also looking to make my kingfisher 20 unsinkable. and i am struggling to find a foam, in slab form that is not highly inflamable, not highly toxic if it is burning, closed cell so it doesnt suck up water in the atmosphere, plus because i need 2 cubic meters the cost is an issue.

answer to original poster. there is a foam called plastizote that fits all spec other than price. for my 2 cubic meters it would cost £2000 approx, so it is out of the question.

i would appreciate if any knows of suitible foam in uk.
there is a guy called the "the simple sailor" who sails his coribee into artic waters, and he has made his coribee unsinkable with foam.

any advise would be apreciated..nick

I looked up the specs on your boat. On a 20 foot boat it ceratinly could be done. This is not something most people would use to cruise offshore anyway so the storage issue is moot.

You 1100 lb keel is Iron. Underwater that weighs 0.86 x 1100 = 946 lb
946 lb / 64 lbs per cu ft (saltwater) = 14.8 cu feet of foam
or 499 kgs X 0.86 = 429.14 Kgs
429 kgs / 1000 kg/cu meter = approx 1/2 cubic meter of foam

Frankly that is a lot of foam but if you broke it into smaller chunks it can be done. You would then have to calculate the flotation needs for the hull and rig, gear, people, and engine if you have one, and add that to the amount for the keel.

Non-toxic non-flammable foam at a reasonable price? I don't think so. Most builders use polyurethane (two part blown foams) or polystryene block foams. Polystyrene (styrofoam) is cheap, it is used commonly as insulation in buildings and can be purchased from any hardware or home improvement store. I bought a sheet recently, 2 ft by 8 ft x 2 in. (2.25 cu ft) for about $12.00 USD. It's easy to work with, can be cut into blocks with any knife, can be glued in place if necessary with epoxy resin and does the job splendidly. The pink or blue stuff (at least here in the US) is closed cell, and is not as friable (pieces breaking off) as regular sytrofoam). I have used it in two boats I built.

If you are worried about toxic smoke from burning foam, by the time the foam catches fire the boat is so far gone you had better have abandoned ship a long time ago. Having fire retardent foam is not going to help. The only place that I know of that it is used is insulation of interior bulkheads on large passenger vessels, where if a fire breaks out, toxic smoke can be disastrous.

[MarkSF]

My Wayfarer came with DIY flotation in the forward compartment - inflated beach balls. No reason you couldn't stuff every locker on a 30ft boat with them.

[delmarrey]

Originally Posted by minaret

For those of you considering weather balloons, etc. you might do some research on boat salvage. I have worked for many years right next door to Divers Institute of Technology, so although I'm not a diver and have no salvage experience, I have watched them raise boats weekly for years. They seem to acquire all sorts of derelict vessels for this purpose. We have been hiring their students for boatyard cleanup help for many years as well, so I talk to these guys a lot. They use salvage bags to raise boats that are very similar to the weather balloon idea, but purpose built for the task. The biggest problem they always run into is that a boat is not designed to take pressure from the inside of the deck. This means that in many cases if you inflate enough balloon to give you the necessary buoyancy to raise the boat, you will just rip the deck off and leave the rest of the boat behind. Often they end up using balloons on either side of the hull connected by a strap that goes under the keel. A lot of rigging is involved. I guess all I'm trying to say is, if you want positive floatation, consider the forces involved for your floatation type and location and beef up the structure accordingly if necessary. Under the V-berth is probably not gonna do it, you'll just rip the top off unless you make sure it's strong enough. We are talking about thousands of pounds of force. I know some production monohulls have done a great job in this regard, the FD12 comes to mind...

Ditto!

Look at pages 26 thru 29 of the PDF/link I provided earlier, it show suggestions of attaching buoyancy. http://files.dnr.state.mn.us/educati...atbuilders.pdf

[Pete7]

Rather than trying to make a yacht unsinkable, why not plan to solve the leak if it were to happen.

Yachting Monthly have been torturing a 40 ft Jeanneau for some months making a series of You tube clips showing some ideas to consider when stuff happens. Worth watching the series:

YachtingMonthly's Channel - YouTube

Yachting Monthly's Crash Test Boat Dismasting - YouTube

[TEE]

I had a Yachtsaver system on a Pacific Seacraft 37. Shortly after it was installed, the company went into bankruptcy. The reason they went into bankruptcy was because their system did not work when installed as directed. They stated the bouyancy bags would provide X lbs of floatation; however, when installed in a boat, due to different shapes of hulls in boats, the bags did not necessarily inflate fully. Thus the boat in which they were installed could very conceivably sink. This was proven in European testing, and the company closed its doors shortly thereafter. Also, the bags were similar to liferaft material and although they were bolted throughout the hull, in order to assure they would hold the gas, they had to be removed inflated and tested periodically, which was absolutely, totally impracticable. Finally, the bags, the hoses and the tanks were spread throughout the boat, and running the hoses, installing the tanks, and the bags took up a lot of space on a small boat. My conclusion is there are a lot of reasons nobody decided to try to fill in the market after Yachtsaver went broke.