Foam filling alluminum hulls

Discussion in 'Materials' started by Guest, Aug 10, 2003.

  1. Guest

    Guest Guest

    Hi there it is I believe the practice to fill a alliminum hull boat with foam,for floatation,rigidity,and it also has sound proofing properties.

    Which Closed cell foam is regarded as one of the best in the long term for not taking in water,over a period of time.

    Any knolledgable recomendations would be appreciated.

  2. Tohbi
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    Tohbi Senior Member

    i've used the two-part pourable foam. most epoxy dealers seem to sell it. i know glen-l has it.

    for flotation, i've stuffed plastic bags filled with styrofoam packing peanuts into areas of the hull.
  3. Roger Marshall
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    Roger Marshall Junior Member

    If you fill an aluminum hull with foam you may prevent air from touching the aluminum hull, which can prevent the aluminum from self oxidizing when it is damaged and eventuallly lead to corrosion. I would advise that you insert buoyancy bags into the hull spaces and fill them with air. That way you can remove the bags and check for corrosion of the alloy.
  4. Tohbi
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    Tohbi Senior Member

    roger makes a good point about accessibility to the hull. probably, in the event of damage, you would be welding from the outside and foam stuck to the inside may ignite. you would have to remove it first.

    if only used for flotation, i like the styrofoam peanut idea because air filled devices need only a tiny hole to become useless. however, pourable foam comes in different denisities with greater or lesser structural characteristics and it makes a boat feel much more "solid" without adding much weight but, coincidentally, adding flotation.
  5. TiggersPups
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    TiggersPups New Member


    We are replacing the deck in our boat and were wondering if we have to replace the foam at all?

    What would happen if we did not use any foam and left the hull empty?
  6. gonzo
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    gonzo Senior Member

    The foam is structural. It forms an I beam.
  7. TiggersPups
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    TiggersPups New Member

    So if it's structural how would bags of packing peanuts be useful?
  8. PAR
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    PAR Yacht Designer/Builder

    The previous posts were addressing floatation, your issues deal with core materials different application, engineering and foam.

    Packing material foam isn't a good idea in a boat for floatation, in a bag or not. When you need floatation to be working is in dire situations (like a flooded, leaking, swamped or capsized boat) and having loose fill in a breached compartment isn't wise and isn't legal in some applications. Your floatation may float way, through the hole that started the leak/sinking etc.

    TigersPups, your foam is high density stuff, must be closed cell and laminated back into the structure for the structure to work properly and as designed/engineered. Most floatation foam is low density stuff and not suitable for what you have in mind.
  9. TiggersPups
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    TiggersPups New Member

    Ok thanks for info. Now we just have to find someplace that sells the stuff. We have called all around and can't any locally, will probably have to look into ordering it. Any suggestions?
  10. JR-Shine
    Joined: May 2004
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    JR-Shine SHINE

    We have the 2 pound foam, and can get 4 pound. A two gallon kit of either gives you 10 cubic feet of foam. Most people go with the 2 pound. If this is a structural repair, you might need something more sturdy as mentioned above. To save money, I have seen some people put empty 1 liter coke bottles in larger spaces before they fill it with foam. It allows them to fill it up using much less foam.

  11. TheFisher
    Joined: Oct 2003
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    TheFisher Junior Member

    Strucural foam (2 part)

    2 part foam of different densities can be found at us composites. They have foam ranging from 2 to 16 pounds per cubic foot.

    I am not affiliated with this company in any way.
  12. Bob Leask
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    Bob Leask Junior Member

    foam filling aluminum hulls

    I've used the two part polyurethane foam commonly available at fiberglass shops, and one problem to be wary of is that it shrinks as it cools. The foaming process is thermal and it gets quite hot, and the adhesion to aluminum is not very good. As it cools the volume reduces quite a bit and it will tend to pull away from the sides forming large voids to trap water.

    I've heard that there are foaming additives for epoxy which might overcome this problem but the downside would be that it might be nearly impossible to remove. On the upside, it may be possible to use epoxy foam structurally.

    To fill smaller voids another alternative may be foamed portland cement. It's heavier than plastic foam (I believe the lightest you can get is around 10 lbs/cu.ft.) but it doesn't burn, and doesn't absorb water. And it's dirt cheap.

    Hope this helps

  13. You might try a foam insulation installer of old houses. Their spray guns can make foam of any density. Question is would they shot a load of marine closed cell foam. Never hurts to ask around. Plus his work should look beautiful and fill it perfectly. offer $$ beer & doughnuts. Those 3 together are better than $$$$$ alone.
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