I was thinking...... After I install my cab corners, I was going to fill them with that can-O-foam (not the fronts, just incase I have to get to the fender bolts). The rears will be cleaned out when i burn in the new corners so there should be nothing bad "locked in".

What do you think? Good Idea or Bad Idea

 

I don't think it's a good idea at all. I don't know if the stuff absorbs moisture, I think it does, if it does you might as well pack it with sponges. I've worked on cheap RVs that the manufactures used the expanding foam as insulation and those areas were the places the the rot started plus it also stinks after it get wet.

Second, if you ever have to work in that area again it's a real pain to weld. I've also worked on old cars that at some time some had the idea to pack them with this stuff. Even if you dig as much as you can out it still sticks and smokes like heck when your welding.

Make sure the insides of your corners are cleaned after you're done welding and prime and paint as you would on the outside.

 

The foam is water proof and doesn't absorb moisture. As a matter of fact I just saw a new variant in th e"Great Stuff" product line that is for filling between rocks in FISH PONDS and WATERFALLS (California.....). I took a class on re-windowing my house and it is a great product when used in the right applications.

I would be very hesitent to use the foam and leave it. Although I have to admit as limited as my welding skills are, and as much as I use fiberglass to patch corners and stuff, the foam makes a good stiff form to shape into a pattern to glass over, THEN REMOVE. If you leave it in in may separate off then if moisture gets in behind it, it will NEVER dry.

Some of th ebad things about the foam are - it's extremely flamible more so when wet, but still flamible when dry - go to weld something later - POOF!. Also, remember that if you seal up ANY rust or moisture, it's going to eat through the panel because it is pinched in between the foam and metal.

If you are looking for something to give you some sound insulation and stop corrosion, I might consider an undercoating spray. But make sure all your work is done before you do it.

 

Why? If you want to waterproof it, put up some eDead or whatever, then you get insulated, have a lot better sound from your speakers and water won't get behind it, but you can remove it if you want. (Think aluminum with a tar underside)