its only bad when its wet

 

i have tried to burn the stuff out from around a mechanisim and all it did was turn black and smell, couldnt burn it for the life of me!

I know my responses are late but hopefully someone finds them useful - if anyone is every trying to do this again in the future: Acetone will disintegrate the foam faster than a spaceship floor in the movie Alien. 

Did you find this out in a bad way? Just curious.

well....after a couple of years the  household style of spray foam disintegrated ,   as the panel rusted the foam fell off to .  but I had a sexy beast of a little while .  I  ended up parting the car out  because of frame rot .   but I got some use out of it first .

well....after a couple of years the  household style of spray foam disintegrated ,   as the panel rusted the foam fell off to .  but I had a sexy beast of a little while .  I  ended upll his wiparting the car out  because of frame rot .   but I got some use out of it first .

Yep, sounds about right. I knew my advice was late. For that kind of repair what I'd do in the future is actually take a dremel and a metal cutting wheel and cut off the parts that are rusted. Then, prep the leftover metal around where you cut and prep it by sanding with a very coarse grit (you want it to be rough, and maybe even slightly below the level of the surrounding metal). Then just use some epoxy to adhere some drywall mesh to the hole and spray your foam onto that. This will add a little structure. Sand the foam so that it's ever so slightly lower than the surrounding metal (almost back down to the screen basically) and then follow my earlier steps to encapsulate the foam in fiberglass and finish it out with sanding. 

 

Rust is crazy, the stuff is like cancer. It just spreads so fast. 

Did you find this out in a bad way? Just curious.

What the acetone trick? Nah, though once upon a time that was found out by accident, it's actually something we use in surfboard repair to determine whether a board is made of PU or Styrene foam. The PU (polyurethane) can handle the acetone but the styrene will disintegrate. The spray can stuff is usually PE (polyethelyne) which will aslo get eaten up by the acetone. 

 

The same thing will happen if you use the wrong resin as well. Using Polyester resin on Polystyrene foam will have a similar reaction, but it will increase the endothermic nature of the reaction - I've accidentally done that and it goes off so hot that the board starts to smoke. 

Do you know of any useful links with more information about these materials?

Do you know of any useful links with more information about these materials?

It all pertains to surfboards, but the techniques are the same. Everything I learned was either off www.swaylocks.com or youtube. Mostly it was a lot of trial and error - I fixed a lot of my own surfboards and built my first two surfboards in my backyard before moving into a professional facility. Lots of learning what doesn't work and what causes more work for you. 

 

You can also check out foamez.com for some cool tutorials on different techniques. 

 

If you want to start doing any real pro body work, look into vac bagging

Ok, I admit that I've used the foam. I once had a 94 Loyale wagon and noticed that the rear carpet would get wet wherever it rained. I checked and found holes in the rear fender wells. I filled the holes with foam, trimmed off the excess and sprayed on some black under coating. Drove the car for another three or four years before other problems forced me to junk it.