Expanding flotation foam....hmmmm...

[michaeljoe]

Just wondering if anyone else has thought of this or tried it.....  I built several kayaks & sneak boats years ago, and used the "Ready Foam" expanding foam sealer.  It's also sold as "Great Stuff", and used for sealing up air leaks in you house.  I tested it on a 12 foot kayak first, and it floated with me in it and full of water.  I used it in chamber I built into both ends of the boat, after the bottom and side panels were on.  Just fill the area, let it swell & expand, then saw off the excess flush with where the deck will be.

[mrthethird]

I'm sure wiser people than me will reply to this, but the biggest downside I know to using expanding foam is that you cannot remove it to check for rot. Any water that gets trapped between the inside of your hull and the foam becomes a prime location for rot. In the minicup I am building, I filled the empty voids with 2 liter soda bottles, hot-glued together so they won't rattle around.

[Charlie Jones]

I also don't care for the expanding foams because they WILL break down and absorb water. I much prefer some styrofoam blocks inside closed spaces, or just epoxy coat with several good coats and close it up, with a provision for a drain.

I've seen the coke bottles used before, hot glued together and that works fine also.

[Hirilonde]

My compartments are tight with access ports, I use nothing due to the problems it can cause.  If I did feel the need for flotation materials I would opt for the bottles as well.  Some pourable foams can break stuff while expanding in enclosed spaces, be careful if you go this route.

[lewisboats]

Just a little trick when using bottles in the northern climes...Put the bottles in the freezer, open for about 15 min or enough time to equalize temps, then seal them. At any temperature above the original freezer's temp the bottles will be over pressurized and it will take at least 15 deg less for them to start collapsing.  It doesn't really matter too much until the bottles go thru repeated freezing and expanding cycles...then they can start to crack. They will also want to part company with any glue holding them together.

Steve

[michaeljoe]

As far as the foam breaking stuff as it expands, I learned taht lesson a long time ago while filling in a hole behind some drywall... lol  swelled out the wall like crazy.  I wound up with a big mess.  I was planning on epoxying the inside of the boat area, then adding the foam before she was all closed up.  I didn't know that the foam would break down.  I have been asking folks all over the place what the life expectancy of the Great stuff is, if they ever saw it deteriorate, etc.  I suppose the coke bottle idea is a good one, and just pull them out & check for cracks every yr?  I could put a few behind the aft bulhead in the transom, too, I guess.  Not too hard to figure out how many bottles I would need for floatation, with a known volume!  Thanks for all of the comments!

[Greg Luckett]

I bought an old, 14ft, sailboat, which now sits down in the creek for the boys to play in.  Its hull was badly delaminated due to foam having been installed via holes in the deck.  It allowed water to sit between the foam and the hull and never dry out.  It had been in that hull for years.  It was still a good deal, as I got a mast which will be used on the Spindrift, and a good set of sails, spars, and a trailer to boot.  The trailer alone was worth what I paid for it.  As a result of finding out what caused that boats delamination, I started using foam block, like Charlie does, but I also anchor them in spots with the spray foam.  This keeps the foam blocks from banging around or squeeking.  I also put in access holes with the little screw in covers, to allow airing.  If the boat sinks or capsizes, it will stay afloat for hours, which is normally more time than the hypothermia window anyway.  To live, stay with the boat, and out of the water as much as possible:  what I teach my boys.

[PAR]

I've used two part expanding foam in many locations and found a way around the "sticks to everything" issue. I pour it into plastic trash bags or pieces of visqueen, used as a liner around the area to be foamed. It'll expand out and mold itself to the area, but it doesn't stick. With some clever use of 1/4" plywood, as dividers (to make the pieces manageable), areas can be cordoned off so the foam can be removed for cleaning, repairs, maintenance, etc.