Does pour foam hold water?

northern rednek

northern rednek

Recruit
Joined
Dec 13, 2009
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Hello,I'm rebuilding a older Banshee ski boat and am ready to start glassing the stringers,transom and floor.I've read that foams will hold water and promote rot.Is this true and does the foam ad much strength to the hull.Is foam really nessary.Would love to hear from someone.
 
BigBoatinOkie

BigBoatinOkie

Senior Chief Petty Officer
Joined
May 28, 2009
Messages
763
Re: Does pour foam hold water?

Personally I like the urethane foam. It is closed cell, so it doesn't absorb much water, if any. Lots of people don't like pour foam and use the pink foam sheets. This a topic that has lots of folks on both sides. I think the foam add lots of strength to the hull and deck. Others may disagree, but I sprayed urethane foam for a living for 7 years, and have seen with my own eyes how foam adds strength to pretty much any structure you put it on. If you use pour foam, I woud suggest pouring it after the deck is on. Cut some holes and pour it in, then glass the piece you cut out back in. My 2 cents. Good luck.
 
Allbutwet

Allbutwet

Petty Officer 1st Class
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May 23, 2010
Messages
209
Re: Does pour foam hold water?

I'm not familiar with your paticular boat. However the two part marine foam is a closed cell foam that is some what water proof. If it is subjected to constant wetness it will eventually become water logged. Besides the flotaion value it also adds sound deading.
 
archbuilder

archbuilder

Vice Admiral
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Sep 12, 2009
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5,697
Re: Does pour foam hold water?

It can hold water if constantly exposed to it on an area where it has been cut or torn. The solution is to seal up any areas that are cut or torn during construction. If it is exposed to constant water, then you have other waterproofing issues to deal with. It will make the hull extremely stiff if it is poured between the hull and deck. It creates what is called a stress skin panel. Essentially it helps to spread stresses on the hull over the entire hull, not just on one concentrated spot.
 
109jb

109jb

Lieutenant Commander
Joined
Jul 15, 2008
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1,590
Re: Does pour foam hold water?

One thing to keep in mind is that the higher the density the less likely it is to hold water. Most people use the 2 lb density pour foam. I used the 4 lb density stuff. The 4 lb density stuff has 2 lbs less buoyancy per cubic foot than the 2 lb stuff. It also weighs twice as much. I used about 10 cubic feet in my boat which means I have 20 pounds less buoyancy and an additional 20 pounds of weight. To me this was a good trade off for having a foam that is much more resistant to water absorption.
 
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