floatation foam

Discussion in 'Fiberglass and Composite Boat Building' started by brokensheer, Sep 5, 2012.

  1. brokensheer
    Joined: Jun 2009
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    brokensheer Senior Member

    any one have any favorites?
     
  2. ClarkT
    Joined: Jun 2003
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    Location: New Orleans

    ClarkT Senior Member

    Ethafoam.
     
  3. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I like hollow chambers, or floatation bags that can be removed. You can use the chambers for storage, and allows you inspect the hull from the inside. Any type of foam you use will eventually get soaked and water logged, adds weight, difficult to remove and replace without major operation. A hollow chamber also adds less cost.
     
  4. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Plain ole stryofoam for flotation. You can get it in any size and shape and can trim it to any size. Never absorbs water. Must be protected from the sun and gas and oils. Had it under a floating dock for 30 years and still good as new. The blue is more expensive than the white though just the same. I have a supplier who will cut it to any size and shape for you. Here is another link for you just one of many I have.http://www.buoyancyfoam.com/ Is compatable with epoxy.
     
  5. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    I beg to differ.

    I do retro-fitment of buoyancy on boats and issues certification therefor and COF's and had boats that were so heavy with water clogged foam, you need a lifting device to pickup the trailer front:!:
    Polystyrene sucks up water like a good centrifugal pump;) and I remove chunks of this stuff heavy as bricks and shaking it, you can actually feels the water moving about.

    In my country the marine authorities prescribed a rigid closed cell polyurethane foam to be used (RX121 & 44V20 type) and although the manufacturers will claim it has basically zero percent water absorption, I removed this foam from a few bass boats in the past that is totally water soaked like a sponge...
    Perhaps their claims are true in laboratories conditions, but in the real world of boating where water get trapped between boat and foam, the slamming and movement of the hull skin leaves the water only one place to go - to break through the brittle cell "skins" into the foam.

    Polystyrene is the better product provided it is sealed. Removed some polystyrene thats 20 years old in boat - foam chips packed in thick sealed plastic bags - that is still as good as the day it was installed. Polystyrene just fitted without protection are only for the brave and stupid.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Some minor differences of opinion on display here. :rolleyes: Polystyrene will be destroyed by gasoline, something to keep in mind. Some say the heavier grade (2kg/cu ft) of PU foam is a lot more resistant to damage and water absorption than its lighter version. Hollow chambers are useless if the hull that forms part of them is breached. Refer RMS Titanic, 1912.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Styrofoam (the Dow product) is extruded polystyrene, not to be confused with the squishy expanded stuff. Real Styrofoam crunches when it's cut. It does pick up moisture over time, unless coated, often with epoxy.

    This is precisely the way all vessels are protected, with the exception of small craft, where interior volume loses can be justified with swamping protection. Compartmentalization is the only reasonable option, foam and bags are just reality in small craft.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I understand that, but presumably life boats are, or should be, mandatory on vessels large enough to carry them. On the typical trailerboat there is no room for self-inflating rafts etc, you really don't want to be on such a hull without foam. Years ago a friend hit a log with a power cat, both sides were very badly damaged, and the outboard legs as well. It was packed with polystyrene on both sides, were it not it would have sunk very quickly, probably with loss of life. I took good note of it.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I wonder whether painting polystyrene with acrylic house paint might offer some insurance against moisture take-up, gloss paint of this type forms a tough membrane and lots of home garages have left-overs, or paint shops cheap mis-tinted cans. Solvent thinned paints will just melt it.
     
  10. Harry Josey
    Joined: Jan 2012
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    Harry Josey Junior Member

    Acrylic paint will work but make it thick with more than 1 coat. You can't seal polystyrene with a quick lick of paint.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Yeah I was thinking at least 2, and possibly 3 coats. The colour would not matter. Would only add minimal weight once dried.
     
    Scuff likes this.
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Single part acrylic house paints aren't very moisture vapor resistant. The two part WR-LPU's are better, but still not as effective as even the lowest grades of polyester resin (which will eat it).

    Had your buddies cat been divided up into compartments, he'd have survived just as well, for less weight too, not to mention the added storage capacity, empty, but sealable compartments can provide.
     
  13. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    Some people just use a load of PET bottles in the space, loads of compartments !
    Would reckon a bit of sealant on the cap would do it.
     
  14. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Re the cat, despite being a seemingly well built GRP vessel, it suffered an incredible amount of damage for what wasn't a very high speed impact, had it been compartments most if not all would have been breached. Under those circumstances the floor level would have fallen below the drain ports and water ingress sunk it. I took the hint and fitted flaps that could be sealed, to the freeing ports on my own similar vessel. Does the US not have mandatory foam in small boats ?
     

  15. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    We have a product that is a closed cell polyethylene foam, UV resistant, most chemicals resistant including fuels and oil, doesn't burn or emit poisonous gasses, can be sawed, milled, cut, filed etc. It's not rigid but flexible. It doesn't absorb water either. Best flotation stuff I ever came across. It even bonds very well with resin so you can glass directly on it. It can also be glued together with almost any industrial sealer. Sondor Industries makes the stuff here. It is also the only true marine foam I know of. The one I use weigh about 32kg/cub meter... for 1000kg displacement.

    Only drawback is it is bloody expensive. Wynand knows the stuff too.

    Doesn't form mildew, pleasant to walk on. If the hull gets holed you can even press a chunk in the hole. Manie uses a piece to jump his whackers (compactors) on prior to renting them out, it even endures such abuse.
     
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