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Thread: Installing Floatation Foam in Your Boat?

  1. #1

    Default Installing Floatation Foam in Your Boat?

    Considering installing flotation foam under floorboards in my 20ft Wooldridge Sport. I want this boat to absolutely not sink even if fully swamped in the ocean. Basic idea is use screwed in place aluminum channel or rectangular tube to raise floor boards 3" and then fill all voids with extruded polystyrene boardstock insulation (does not absorb water). By my calculations, rasing the floor boards 3", and after accounting for lost space due to gas tank and structural members, would net me about 42 cubic feet. Boardstock weighs 5 lbs/cubic foot so net bouyant uplift force would be 2400 lbs which is about 240 lbs more than boat, main engine, kicker, anchor etc..... Fuel floats so any empty space in the fuel tank is a bonus. I am pretty confident in my math and measurements, so the question is:

    Anybody done this themselves and have any pointers?

    Any speculation on if the handling of the boat would change noticeably due to lifting the floor boards (and thus any weight inside the boat) by 3"?

    Glen Wooldridge told me DO NOT pour foam it because pour foam water logs over time, and will trap water and then cause problems when the trapped water freezes in your driveway in the winter.

    The other option is foam in the side trays and under the existing floor boards, but then you lose all that storage

    The other option (much easier) is to foam under the existing floor boards, and also completely foam under the bow.

    It was interesting to learn that only boats 18ft or less are required to have flotation, and the actual test procedures for "full level flotation" are not very well defined, i.e. with or without engine? with or without typical bolted on or entrapped objects in storage space typical on most boats?, loss of bouyancy over time due to foam water logging? Boats over 18 ft are not regulated and each manufacturer comes up with their own criteria for what they think flotation means when or if they foam their larger boats..............

  2. #2

    Default Fuel tank question?

    Is your fuel tank air tight or does it have a air vent? I've had the misfortune of watching a boat sink in the ocean and it had vented fuel tanks, they didn't even slow it down. The only slowing process was the air caught in the bow. Just a thought for you.

  3. #3
    Moderator AKmud's Avatar
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    We ended up pulling all the polystyrene out when we found it was waterlogged. It is supposedly waterproof and won't absorb, but when a 1 sq' piece x 2" weighs in at around 12-15#s, something is wrong. I figure once we got all the wet foam out of the boat, we lost about 150-200#s of dead weight in the hull. Our boat is a bit older (early 90's) so technology may have advanced, but we weren't impressed.
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    Default

    Quote Originally Posted by AKmud View Post
    We ended up pulling all the polystyrene out when we found it was waterlogged. It is supposedly waterproof and won't absorb, but when a 1 sq' piece x 2" weighs in at around 12-15#s, something is wrong. I figure once we got all the wet foam out of the boat, we lost about 150-200#s of dead weight in the hull. Our boat is a bit older (early 90's) so technology may have advanced, but we weren't impressed.
    I did the same. Removed all the foam. I also lost about 30lbs. of sand that gets trapped in the hull even when we flushed the it well.
    The weight savings made both of the boats handle better and let me haul more (fuel,fish,bld.supplies,meat). Not only that but i can hit real skinny water too.

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    Member potbuilder's Avatar
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    Take piece of that foam stick it in a bucket of water with a weight on it to sink it then let it soak for a month and see what happens. I bet it will be waterlogged.

    Steve the potbuilder
    alaskashrimppots.com
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  6. #6

    Default

    You are not the first person I have heard wanting to foam there boat to make it float. I would think your going to have a water sponge/dirt collector instead of floatation in no time. Some buddies and I had a three bench seat row boat, (like a Lund) with big blocks of foam inside/under the seats, completely empty of anything, and I mean ANYTHING! We used it for swimming and messing around with in the lake, we flipped it upside down to mess around with while we swam. It had the bouncey of a sheet of plywood, if you climbed on it, it sank! It was great fun! I bet you would have to build a Boston Whaler before your going to get enough foam in an aluminum boat to make it float like you want it to, with gear, engine, fuel, etc.

  7. #7
    Member Xerophobic's Avatar
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    Default

    If possible locate a company that specializes in blow-in foam or foam designed specifically for this purpose. (your local coast guard regulations likely will have a foam spec for exactly whats required) Even if they do blow-in you can make simple molds to meet your needs without blowing it directly into the hull. Install it "loose". I think most advice here is on the money don't use a product not designed for this exact purpose. You also may want to consider the foam being resistant to fuel and oil etc

    Wrapping foam blocks in shrinkwrap also prevents peices from breaking off and making a mess.

    Cheers
    Skinny water addict

  8. #8
    Member breausaw's Avatar
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    Quote Originally Posted by ltsryd View Post
    Is your fuel tank air tight or does it have a air vent? I've had the misfortune of watching a boat sink in the ocean and it had vented fuel tanks, they didn't even slow it down. The only slowing process was the air caught in the bow. Just a thought for you.
    Fuel tanks must be vented or your fuel tank will pull a vacuum and starve the engine. Most boats have a float valve or breather that will plug if immersed, but if theses vents are not maintained properly they could fail. Once a water filter type vent is immersed it is usually plugged for good and needs to be replaced.
    Jay
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  9. #9
    Member JOAT's Avatar
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    Default Foam = Water

    This is one area where the Coast Guard has it all wrong. Foam absorbs water, plain and simple. Look at the construction of foam. It is basically a plastic with lots of air bubbles in it. Some foam will take longer for those air pockets to fill with water, but eventually they will.

    Having worked with a custom aluminum boat builder, I know he always designed in trapped air as part of the construction. Takes a lot more work to get a completely water/air tight container, but it gives you the maximum buoyancy. He did some remodeling of one of his boats last summer. It was over 20 years old with trapped air tanks in the floor. He was redoing the floor design due to a change in the primary purpose of that boat and when cutting out the old floor tanks, there wasn't a single drop of water in them. Find me a foam block that has been sitting in an open skiff, outside for 20 years, that isn't waterlogged.

    Unfortunately, the Coast Guard doesn't think that trapped air counts as flotation. He did lots of projects on mass produced boats that required removal of all the original foam. Some of the boat owners would replace it with new foam and others would just dump it. Depended on the application and level of Coast Guard inspection they required (i.e. commercial use requires the flotation).

    The chemical pour in foams are not even water resistant. They will waterlog very quickly and are a royal pain to remove. They are also generally weak foams and will not handle very much stress before breaking up.

    If you really, really want to have foam flotation, just plan on replacing the foam every few years and design your mounting system to be easily removed. If you can keep the compartments with the foam in them ventilated and perhaps even pull up the foam for winter and keep it in warm storage to completely dry out, you might get considerably longer life out of the foam. But you're talking about a bunch of extra work for your pre & post-season maintenance.
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  10. #10
    Member AKDoug's Avatar
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    Default

    All extruded polystyreen (Dow blue board and the Owens pink stuff) will absorb water.

    All expanded polystyreen (Insulfoam or Styrofoam) will absorb water.

    Don't listen to any salesman telling you otherwise. I sell the stuff and they will absorb water...period.

  11. #11

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    Even a Boston Whaler can get waterlogged, and some do.

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    Default Regs...

    This might be helpful here.... http://www.access.gpo.gov/nara/cfr/w...cfr183_04.html

    Mike

  13. #13

    Default A little farfetched....

    How about ping-pong balls? I heard somewhere that they (and the air trapped inside of them) provide an unbelievable amount of flotation, enough to float a sunken vessel???? I know it sounds crazy, but somebody's got to walk the plank.
    Jim

  14. #14

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    How about the closed cell foam? Spendy but would work. Buy funoodles in bulk and cut to fit. The 3 inch by 4 foot has 200 plus lbs of lift, I bet you could get more than 12 in under the floorboards then you could stuff the stuff in all the crannies.

    For that matter you could buy big hunks and mount it to the outside of the boat like the old purgue and some canoes, would be rub guards and flotation.

  15. #15
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    Default closed-cell foam

    [QUOTE=alaskamokaiman;181670]How about the closed cell foam? Spendy but would work. Buy funoodles in bulk and cut to fit. The 3 inch by 4 foot has 200 plus lbs of lift, I bet you could get more than 12 in under the floorboards then you could stuff the stuff in all the crannies.


    Sounds like a great idea. If nothing else, you wold have a lot of flotation bobbing around if you go down. I would check compatability with gasoline though.

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    Default Weldcraft foam

    I cut out some rear storage bins in my 03 Weldcraft. see pic. I left 2-3 inches of foam on the bottom and the holes were only as wide as the hatches I installed. that left basically a foam bowl. after coming back from a fishing trip, there was about 4" of water in both sides from sitting in rain all day and seals of hatches didn't hold I decided to do a test and see if the foam would soak it up. planned on making openig bigger anyway. 3 weeks. hatches covered with tarp so no more water could get in. same amount of water was still there on return. kinda nasty though. after cutting out foam to enlarge opening, the foam was light as a feather. They had told me it was a foam that wouldn't absorb water, but I had to test to believe. I would contact Weldcraft Marine and ask which floatation foam they use.
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  17. #17

    Default

    I spilled 1 gallon of gas in my Mokai on a trip from Whitter to Seward no effect on the closed cell foam.

    I had the spray skirt on and did not know that one of the cans of gas tipped and was not sealed properly. Beached to refuel and found the empty can.

    I think that you could get the funoodles in without pulling the whole floor just enough to shove them in place.

    Cheers,

  18. #18
    Member sayak's Avatar
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    Default This has been done

    Quote Originally Posted by Big Jim View Post
    How about ping-pong balls? I heard somewhere that they (and the air trapped inside of them) provide an unbelievable amount of flotation, enough to float a sunken vessel???? I know it sounds crazy, but somebody's got to walk the plank.
    Jim
    I heard that Howard Hughes did this in the wings of one of the planes he flew across the ocean.
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    Default Mythbusters

    On a show they raised a boat they sunk, heavy old fiberglass one. It took a lot of balls to raise it but may not take as many to keep it from sinking. I used Tuff Stuff brand spray foam you see a lowes or home depo. If I remember correctly it took 13 cans to my 22' boat. It is closed cell foam and we tested it over night in gas and water. I had to remove some foam in the bow a few falls a go. There was water under the foam in a couple spots but foam was not soaked. It was probably just condensation or from where water got into the boat from the hole I put in her. All of my foam is easy to get to if I pull up the floor. I think if your application it should be fine too. I did mine just for insulation and to cut down on noise.
    Last edited by akrstabout; 09-18-2009 at 21:49.

  20. #20

    Default

    I know of some people who have fiberglass boats who are having to pull their aluminum gas tanks out and replace them because they corroded. My understanding is that if you make it so that water can't drain away from the tanks (e.g. if you have leaves, other debris, etc. that can hold water and it's up against the tank), then it can lead to corrosion. Especially true if it's salt water. So I wonder if foam, when it's next to aluminum, regardless of whether the foam absorbs water or if it just doesn't allow aluminum to dry, will cause aluminum to corrode.

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