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Thread: Boat Foam Question

  1. #1
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    Default Boat Foam Question

    Thanks for all the advice on boat tops. I'm scheduled at Silverstreak in 2 weeks for a new top on my Hewescarft river runner!

    The next question on my project boat has to do with foam. I pulled up the plywood decking which was rotting in places. Underneath I found a bunch of water logged and rotting foam. Probably pulled out over 200 lbs of wet plywood and foam!

    So I'm in the process of fabricating a new deck. But I'm not sure about replacing the foam. Does anyone have any experience with this problem? Any suggestions on what I should use or if I should even replace it?

    Thanks,
    JBK

  2. #2
    Member Akgramps's Avatar
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    Default Foam or not to foam

    Silverstreak sprays closed cell foam in the bottom of their boats when new. The foam (if not waterlogged) will give you some floation, could be important if you capsized.
    Also the foam will make the boat quieter, which is always a good thing in my opinion.
    What type of foam was in your boat?
    How old is the boat?

    Akgramps

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    Default

    Some folks use blueboard. Should not soak up the water like the common spray in stuff. There are several types of spray in, some of which claim to not be affected by water. I've been told to be wary of these, but haven't talked to anyone with actual experience. While your deck is off check welds to make sure everything is intact especially with your fuel tank mounting.

  4. #4
    Member Akgramps's Avatar
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    Default Waterlogged blueboard

    Roscoe,
    Blueboard is extruded poystyrene and can absorb water if sumberged in it for long periods, I have had some one hand me a piece that was removed from a commercial roof job and it was as heavy as brick!
    I dont know how long it takes for that to happen?

    It would be interesting to hear from people that have experience with the sprayed in place type.

    Akgramps

  5. #5

    Question Placement of foam???

    Anyone ever thought about getting the foam separated from the bottom by say fractions of an inch at least to let the moisture pass/drain from the foam? Any chance getting it up on spacers or off the final surface, on plates or something like it? Make it so the foam isn't able to "marinate" in water, the water would drain, the foam could dry and recover. This idea came to mind one day when I lifted my v-berth cushions and found the compartments had a small amount of water in the bottom. I thought that it might very well be condensation accumulating after a long summer of sleeping in it. Double hull tankers, bilge water routes, water flow directed to the plug, etc, you get the idea.

  6. #6

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    The spray in foam works great as long as whoever sprays it in first places a vapor barrier in the cavity to be filled and then ensures that the foam is completely sealed in the barrier after spraying.

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    Member akrstabout's Avatar
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    Default Great Stuff

    I think it is called, every where carries it. The red and yellow cans. It cures into a closed cell foam. Used in my boat, 22 or so cans. Has not soaked up water. Just make sure not to poke holes in it. We put a piece of sprayed foam in water and I think gas, can't remember. Whatever it was it never soaked up any water. It bonds good to aluminum. Just make sure not to spray it too thick, it doubles in size at the least.

  8. #8
    Member pta's Avatar
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    Default Be carefull using just any foam...

    The foam used by the boat builders is rated for exposure to gasoline in case of minor spills. A lot of the other foams out there will completely desolve into a nasty mess if you get gas or oil on it.
    You could also try filling the underfloor spaces with empty plastic beverage bottles or ping pong balls... I seem to recall the Mythbusters floating a sunken boat by pumping ping pong balls into the hull

  9. #9
    Member Akgramps's Avatar
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    Default

    Lastsplash,
    It seems you are speaking of some type of vapor barrier, which the correct foam should be a vapor barrier anyway, trying to install a VB over stringers and reinforcements sounds like a severe pain in the derrier.
    And any breach in the VB would allow moisture in and then trap it.?
    I think when the foam is sprayed in it is done in such a way that it wiil allow water to drain the lowest point (middle) and then down to the bilge pump, so unless you leave your plug in when you pull your boat out or have left the bow low the water should drain to the back and on out.
    Like so many things, proper execution is the key and make not work in all applications.
    my 2 Lincolns.................for what its worth.......
    Akgramps....

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    Default

    Thanks for the tips...

    I think I'm going to go with a spray in foam and protect the drain channel at the keel. That should help with drainage. I'm also going to paint the interior shell of the hull with Durabak marine paint. Then install the floor boards on top of the foam. I'm going to use quick disconnect fittings so I can pop the deck off after using and let the foam air dry.

    www.durabakcompany.com/marine2.htm

    I'm probably over doing it, but I needed a project to keep busy and the wife likes me out of her hair!

    Cheers,
    JBK

  11. #11
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    Default foam

    Akgramps you are absolutely correct. I work for the largest commercial roofing contractor in Ak. We tear off and replace roofs done with every type of insulation that has ever been manufactured (board and spray on). All foam insulations will absorb water over time!!! The type of insulation will determine how long it will it take for that insulation to become saturated when exposed to continuous water exposure. Pertaining to the questions here, there are "below grade" insulations that are more impervious to water absorbtion than others but anyone wanting to use them should check with their supplier for their recommondations. I would personally avoid any spray-on types - they have proven to be the least effective in my observations. Myers is correct in stating that allowing moisture to pass by the insulation on the way out and not sit soaking in it will help. Pta is also correct in statng that not all foams are resistant to fuels. Again - check with you supplier!

  12. #12

    Default

    Buy a bunch of funoodles and cut and fill the space they will not hold the water. A 3 inch round by 4 foot floats 200 lbs.

  13. #13

    Default 3-inch diameter x 4-foot long object only floats 12 pounds!

    maximum possible bouyant uplift = weight of volume of water displaced
    volume of cylinder = area (length) = pi (r)(r)(l)
    volume in cubic feet for 3" diameter x 4' long object:

    3.14(.125)(.125)(4) = .196 cubic feet
    water weighs 62.4 lbs/cubic foot, thus
    maximum uplift of a single 4 foot long funnoodle = .196(62.4) = 12.2 lbs not 200 lbs!

    The reason these things float kids is our bodies are mostly water and nearly float anyway (that is why most life jackets provide from 11 to 33 lbs bouyant force).

    If you fill your boat with funnooodles assuming 200lbs per noodle....the boat will sink. I ran bouyant uplift calculations for my 20 foot wooldridge and concluded I would have to raise the floor boards about 3 inches and fill all voids entirely with foam to barely get neutral bouyancy if swamped. considering the weight of the hull, engine and other bolted on objects, or stuff inside locked compartments. Wooldridge boats agreed with me............

    The end result for me after much painful analysis and research of all alternatives (because I have a soft top and have no good way to carry an inflated raft, and inflated tied down rafts are hard to deploy quickly in an emergency, and typically do not hold a lot of people unless they are 10 feet long........) is I just bought Revere Coastal Commander valise style 6-man deployable self inflating life raft for $1725 from Eagle Enterprises.........

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