Spray foam question

[Blackjack-sven]

I have this foam that I picked up at my local hardware store called "Great Stuff" but I'm not sure if I should use it. The can does not tell me the lb rating. Does anyone know whether or not I can use this stuff?

[Doby]

I use it in all my boats for several years now and it works great. Just make sure to do small portions at a time. If you have a big cavity to fill, do it in small doses over several days, that way you will minimize any potential for over expansion.

[Blackjack-sven]

Perfect, cause I want to add some of this foam to the rear of my BJ26 BL, so if flipped the ass end will stay afloat with the front end while I bring out my rescue boat to push it ashore. This way my electronics will stay nice and dry without having to balloon everything.

[Steven Vaccaro]

I'm not sure, but I think this is the stuff that other people have said will expand well after the cure when exposed to sun light. I'm not 100% sure, just do some searching to make sure or don't fill the cavity completely.

[longballlumber]

this stuff will absorb water over time too... Personally, I would use something different, but that is just my $.02

[Doby]

It does not absord water.

[bustitup]

how feasible would it be to spread some of that under a mm hatch cover...say like 3/4" thick to the hatch would float?

[paulwilliams]

It does not absord water.

Maybe there are different brands? We have some canister foam we used in a small monohull that flipped and filled. For various reasons, it took us a few hours to retrieve it. By the time we got to it, the foam in the nose had absorbed a lot of water and the boat was only just still floating.

The 2-part stuff you mix up I think is waterproof, the aerosol stuff, from my experience anyway, does absorb water.

Paul

[Rex R]

bustitup: apply in small amounts or else the hatch will warp. remember to check to that everything will clear before you mash the hatch down to tape.

[Steven Vaccaro]

When I was about 14, my cousin gave me a half built pt-109 to finish building. I put in a ton of the spray foam. Then let it dry over night. I was in amazement when I woke up the next day to see a GIANT amount of foam budging from the hull. What a newbie! After some cutting away it worked fine. But I never did finish the boat. This reminds me to go to my parents house and see if its still in the basement.

[longballlumber]

It does not absord water.

My mistake.... I still woudn't use it....

[Blackjack-sven]

My mistake.... I still woudn't use it....

Why not?

[longballlumber]

the risk factor keeps me away from it...

expansion rate is a guess at best
others have mentioned issues about continued expansion in the heat
some are saying it will take on water other say it wont
It's heavy in respects to other "foam" products.

There are many other alternatives that don't have the same level of risk...

again just my $.02

[paulwilliams]

expansion rate is a guess at best

Expanding foam also shrinks when it gets cold. I used it in the front end of a lightweight epoxy Hopf Evo that I built at the end of the summer last year. A month later, the temperature drops and suddenly my Evo has wrinkles in the deck

To be fair, this hull was a very light layup.

Paul

[Jeff Wohlt]

I have found two kinds. One is a waterbased white foam. it is the kind that is easy to crumble up and very soft. I had to put some in a window frame and it gets hit by sun all afternoon and has never expanded. I will try and find a name. Neat stuff but it will not give the hull more support where the yellow crap will.

Always allow enough room. If you block it and it grows then boom.

I like the hatch idea if you could spray a layer in it...certainly it would float but the good old bathtub is where we find all this out for sure.