# Using spray foam to seal a leak



## Survivor (Aug 7, 2008)

I have a leak where I can't get to the bolt head because it is under the mast. Theres just enough room for a spray straw to get between the bottom of the mast and the mast support. Has anyone used a sprayable waterproof foam to do a 6 month fix. This spring I'll drop the mast and do the fix properly.


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## Maine Sail (Jan 6, 2003)

*It sounds*

It sounds like the water leak is originating at deck level and dripping through the deck into the cabin. The problem with sealing leaks from inside the cabin is that the water is usually passing through a cored laminate, which on your boat is likely to be either plywood or end grain balsa.

If you seal a leak on the inside you will force this water, that is still leaking in, into the decks core with no chance of escape into the cabin.

I would suggest letting it leak until you can effect a proper repair as it will force less moisture into the core material by allowing an escape route..


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## Survivor (Aug 7, 2008)

I'm sorry, I wasn't clear enough. The application would be at deck level in the small accessable area I have under the mast but above the mast plate, not on the inside.


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## Maine Sail (Jan 6, 2003)

*Pic..*

Can you get us a picture??


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## AllThumbs (Jul 12, 2008)

I would say do whatever works. Anything is better than letting it leak into the deck core all winter.

Eric


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## Idiens (Jan 9, 2007)

Test a sample of foam in a bucket of water for 24 hours. Some of those foams are not actually water proof but water absorbent.


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## sailingdog (Mar 19, 2006)

Idiens has a good point... many of the spray foams aren't really waterproof. Stopping water ingress without complicating any future repairs is what you're trying to do... and a spray foam may not do the trick. A photo would help.


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## Quickstep192 (Jan 6, 2001)

Some of the expanding foams that I've used form a skin that may resist water, but once you get through that skin, they're a rigid sponge. As a temporary fix,it might be OK, but would be low on my list because the stuff can be hard to remove after it fully hardens. 

PS, Polyurethane glue (Gorilla glue) is basically the same thing as expanding foam, but doesn't expand as much. It could be placed using a syringe. I mention this because it's initially thinner than expanding foam and might find its way into you leak better.


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## sailaway21 (Sep 4, 2006)

Tho9se low expansion foams do not seal water leaks for beans and they're no fun to remove either. Don't waste your time trying with that stuff.

What you might be able to do though is use a syringe and a tube and squirt some unthickened epoxy in there.


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## Survivor (Aug 7, 2008)

Sorry, I don't have a camera but I'm not going to use the foam. Thanks for the feedback.


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## bshipp (Dec 18, 2004)

I've also had success with Cap'n Tolley's creeping crack cure, if the leak isnt too big.


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