Great Stuff expanding foam?
 

Anyone think of using this to seal up gaps and then just painting it?

I'm planning on using it to fill in the top grille and some vanity holes in the body kit on my xB, cover with a skim coat of bondo, then painting it all rattle-can flat black.

When I do eventually get around to doing this, I'll be sure to post here.

i was thinking about using that to fill some of the gaps under the body like around wheel struts and stuff where it would not be visible. it easily be carved to shape. i vote its good stuff

Make sure it doesn't get sunlight on it. It almosts melts in UV radiation.

Make sure it is well-supported. It isn't very strong by itself. It does adhere to literally anything - including Teflon.

You can use it to fill gaps. Just make sure that whatever gap your sealing you do not, ever, ever want to unseal. Also make sure you use disposable gloves. That stuff sticks like mad and once it is stuck the only way to unstick it is to cut, saw or sand it off.

It may work as the OP has suggested, but may not be a good material for large, built-up type construction. I've read several threads where it hasn't worked as well as hoped. The latest I can recall is MetroMPG's kammback.
http://ecomodder.com/forum/showthrea...sion-3518.html
See post #66.
The two-part stuff that is mixed together may work better, like the thread showing an artist and his highly modified car:
http://ecomodder.com/forum/showthrea...ting-2793.html

But I've never used any of this stuff.

See how smart you can get by reading threads on ecomodder.com? :p

Any one have other suggestions about what to use to fill gaps? What about silicone?

I like outdoor clear silicone for sealing and adhearing things to my bicycle. It holds great, yet can be peeled off without too much trouble. I has withstood winds in excess of 75 mph and remained in place.:thumbup:

You mean like the silicone you can get for sealing bath tubs? What would be the best stuff to get? I'm not looking to build on this, I just want to seal up all the gaps in the front, but be able to paint it so I looks half decent.

Great Stuff used to make a black expanding foam for landscaping (like garden ponds and such-- my dad has used it in his), but it appears they don't anymore. Reading the Great Stuff site, however, they do specifically recommend painting the foam in applications exposed to sunlight.

I have, however, found this:
Pur Black NF Expanding Foam - Foam Products - Pond Accessories

It seems kind of pricey, but is meant to be used outdoors, and will allegedly withstand heat, cold, moisture, and light.