boat foam?

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todhunter

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Foam for where? Under the floor? You'll want to use a 2-part expanding foam. It comes in various densities (pounds per cubic foot). I used all 2 lb foam for below the floor of my restoration project, and I bought it from US Composites. Follow the directions, and mind the ambient temperatures - too cool and it won't expand / yield as much as you are expecting. It likes it HOT!
 
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brodyg201

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todhunter said:
Foam for where? Under the floor? You'll want to use a 2-part expanding foam. It comes in various densities (pounds per cubic foot). I used all 2 lb foam for below the floor of my restoration project, and I bought it from US Composites. Follow the directions, and mind the ambient temperatures - too cool and it won't expand / yield as much as you are expecting. It likes it HOT!
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ok yeah for under the floor on a 81 starcraft supersport 16ft
 
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froggy1150

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If there is structure under deck, stringers and bulkheads, 2lb foam. Flotation only. If there is no structure your foam needs to be structural, 4lb foam.
 
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cyclops222

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I sure hope it is CLOSED CELL FOAM rated for use with oil and gasoline. It is used in floating docks. Open cell will soak up all the water that touches it.
 
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brodyg201

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could you use expanding foam but maybe put it in like a trash bag or something so if i need to get back under the floor it’s not all stuck to everything?
 
rolmops

rolmops

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I redid the flotation foam on 3 of my Islanders. The problem with poured expansion foam is that it sticks to the bottom and it does not allow water to drain.No matter how closed cell the material is, it will eventually start absorbing water because the water has nowhere else to go. I believe that I solved the problem by laying plastic bubble packaging material in the bottom of the boat and pouring a very thin layer of foam as a first layer. This overcomes the problem of the foam sticking to the bottom and it also allows for drainage of water to the bilge by streaming through the bubble packaging. The foam gets hot as it expands and the higher the temperature outside the faster the foam expands and the hotter it gets. Hence the first thin layer which, because it is thin, expands and dries fast but does not get so hot that it may melt the plastic.
I'm sure there are better ways,but it seems to work .
 
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cyclops222

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PVC foam is not damaged by gasoline or oil. Water can not burst the closed cell foam. Or floating docks would sink. Ours are over 15 years old. Like new.
 
rolmops

rolmops

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cyclops222 said:
PVC foam is not damaged by gasoline or oil. Water can not burst the closed cell foam. Or floating docks would sink. Ours are over 15 years old. Like new.
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Water can burst PVC foam. If there is a small crack in the foam water will penetrate and stay where it is. In winter, this water will freeze and expand, thereby making the cracks deeper. Every time this process repeats itself , the cracks will get bigger and more water will penetrate. This is how the closed cell foam in boats fills up with water. I suggest that you pull one the floats and put it on a scale to see how much it weighs., so you can see for yourself. It should weigh 4 pounds per cubic foot. A cubic foot of water is about 7.5 gallons or 60 pounds. add to that the original 4 pounds of foam. I'm sure your floats don't weigh 64 pounds per cubic foot, but I'm also sure that they weigh a lot more than 4 pounds.
 
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MikeSchinlaub

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cyclops222 said:
Our dock floats sit outside all winter on N Y Canada border. Mink and Muskrats chew out holes all the time. No sinkings or replaced foam.
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It wouldn't necessarily sink even if it's taking on water. My barely understanding it explanation is that displacement + density + air trapped in the non damaged foam = thing floats.

Brodyg201, I wouldn't isolate the foam from the structure. Every one I've taken apart has always had the foam poured straight into the cavities. Bonding to the hull, stringers, and floor will give it all some support. Putting it in trash bags would take away the structural support, but still leave you with the added buoyancy.
 
Scott Danforth

Scott Danforth

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foam takes years to decades to break down due to freezing and thawing cycles

if you prevent water from getting under the deck sole, the foam will never be wet.
 
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brodyg201

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i’m thinking about going with just the foam sheets just cause i don’t like the idea of having to tear expanding foam out if i ever have to etc i was seen about rapping the foam board in a special kind of trash bag that has can’t eat through . any suggestions on that idea ?
 
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brodyg201

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now i have a question i was going to replace the foam when i do the floor and the floor is only soft in one area in the back and i was just going to only replace like a 8 long peice of the floor up to area by the wheel and leave the front but replace the foam in the front to from trying to squeeze underneath the front . i guess my question is should i just replace all of the floor or do it where i dont have to remove the bow seats and the wheel etc ?
 
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