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> What epoxy can I use over styrofoam?, Working on a 1 piece front end
groot
post Jan 2 2006, 12:14 PM
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So, I'm building up the top of my steel bumper to have it blend smoothly over the hood. This part will be used to pull a mold, which will be used to make a CF 1 piece front end for my race car.

I've got a 2" section of styrofoam on top of the steel bumper and need to attach another 1/2" of foam to it and then seal it up. I have a fiberglass repair kit and the epoxy that came with it just eats the styrofoam.

Any suggestions?
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GWN7
post Jan 2 2006, 12:17 PM
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wax paper over the foam or plastic wrap (check to see if the epoxy eats the plastic wrap first). The epoxy won't stick to them but it won't eat them either.
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ArtechnikA
post Jan 2 2006, 12:19 PM
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if it's not structural, i think vinylester resin would be a better choice and i think is styrene-safe. or possibly Saf-T-Poxy...

since this is a popular technique for forming custom tanks in the experimental aircraft community, the should be product use guidance at Wickes or Aircraft Spruce.

i have a book on composite aircraft construction - but it's packed far away...
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Brian Mifsud
post Jan 2 2006, 12:22 PM
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"Clarks Foam" as is used in surfboard making is immune the ravages of epoxy.
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toon1
post Jan 2 2006, 12:22 PM
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polyester resin eats foam, I have been told by some aircraft guy's that epoxy type resins don't eat the foam.
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groot
post Jan 2 2006, 12:25 PM
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Cool...

I found this out: "Polyurethane foam can be covered in both polyester and epoxy resin. Some foams are dissolved by polyester resin, so if there is any doubt about compatibility test a scrap piece in the polyester. If the foam melts, repeat the test using epoxy. Epoxy does not usually attack most foams, but if it still melts it is necessary to find a different foam material."

from this website:
Fiberglast website
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groot
post Jan 2 2006, 12:27 PM
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And sure enough the crap I got in the fiberglass repair kit is polyester resin.

Thanks!!
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bondo
post Jan 2 2006, 12:32 PM
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QUOTE (Brian Mifsud @ Jan 2 2006, 11:22 AM)
"Clarks Foam" as is used in surfboard making is immune the ravages of epoxy.

Bad timing...

Clark Foam
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Borderline
post Jan 2 2006, 12:32 PM
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(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) Are you sure what you're using is an "epoxy"? Epoxy shouldn't eat the styrofoam. "Polyester resins" that are used most of the time with fiberglass will eat up styrofoam but the epoxy shuldn't. Clark Foam (out of business now...no more surf boards) is a polyurethane foam so it doesn't get eatin up by the "polyester" resin. You should know if you're using epoxy as it a lot more expensive than the polyester resin. My bet is that you have a polyester resin and just need to find a real epoxy. Good luck and post some photos when you're done... I'm planning eventually on doing something along the same lines. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

Bill
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r_towle
post Jan 2 2006, 12:53 PM
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If you are using pink foam from HD, you need to be looking at using silicone or vinyl adhesive.

If you are using blue foam, it tends to be ok with oil based adhesives.

If you are using true modeling foam from a place like www.foamation.com, you can use resin based adhesives...

It the first two, and quite possibly in the third, I would use sheetrock joint compound on top of it before you try to pull the mold.

My son makes alot of scenery and this is the normal approach...contsruction adhesive workd well also...

The joint compound works perfectly, is easy to shape and does not produce alot of heat during the curing process.

I would use joint compound, then paint and sand and wax it before you try to pull a mold from it.

I got a great book at the local bookstore that is all about working with fiberglass,,,it shows alot of those techniques.

Also, do not use the wifes scissors for the carbon material...whatever scissors you use will be dull very soon after you are cutting the carbon...its just the normal problem with carbon.

Rich
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Mark Henry
post Jan 2 2006, 01:07 PM
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Regular white wood glue will work.

I've made many a mold out of styrofoam by painting it with white glue then covering it with paper and painting more glue over it.
Once it's cured just wash it out with thinners and the foam is gone. Then wash it (soak it for a while) with water and the paper and glue is gone.
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