Insulation foam question

[Dustfinger]

I've recently found myself in possesion of some rigid insulation foam, and was hoping I could use it for some prop building. Is it possible to carve the foam to the desired shape, cover it with fiberglass resin, and not have the foam melt away because of the chemicals in the resin?

 

[Honus]

What color is the foam? Blue and pink insulation foams can be cut with a hot wire cutter, other foams can give off toxic gas. Any foam is fine to cut with a saw. Polyester resin will melt foam- you'll have to use an epoxy resin. You can also cover the foam with an acrylic sealer like Minwax Polycrylic. That will keep paint from melting foam- it even works with fibergalss cloth but it won't be as strong as epoxy resin.

 

[Dustfinger]

Thanks for your help. I'm using the blue foam luckily. I'v been wanting to do a project like this, and now I know how. But because I don't have that sealer now, would any other brand of sealer hold up against the fiberglass?

 

[Dha Syntir]

I've heard of folks covering the foam in Bondo until it's seemingly as rigid as the fiberglass. Is that true, and does that method work? I had thought about using some of the blue foam/bondo to create a home made jet pack. Anyone seen any created like that and are they horrid looking?

 

[TeamFett]

If you use too much bondo then it can crack easily.

 

[GrottyFurball]

fiberglass reinforced bondo doesn't crack too easily, I used it making my cod.

 

[TeamFett]

Yes but if you cover the entire thing with bondo, then the flexing will cause it to crack. Fiberglass reinforced is a different story, though.

 

[Dha Syntir]

Where does one go to learn about working with fiberglass? I mean it's not brain surgery, I'm sure with some good reference material I could learn how to work with it. You would begin with making a cast of the jet pack in question. That's another skill I'd like to master-any help there guys? Then you'd put on some kind of oil on the mold and begin putting on layers of resin and fiberglass cloth, hopefully ending with a jet pack in two pieces so you can use the mold again, with a perfectly smooth surface, no? I understand that's a generalization to say the least, but is that about right?

 

[TeamFett]

Yeah you pretty much got it. Fiberglassing is the easy part. Making the mold is a pain.

 

[Honus]

I have a book called "The Fibreglass Manual" by Keith Noakes. You might see if you can find it- it's one of the better books I've seen on working with fiberglass.

I had considered making my jet pack out of blue foam but I didn't have enough so I ended up making it out of cardboard instead. There's absolutely no reason why foam wouldn't work. For the main body I'd make templates and use a hot wire cutter to shape it.

 

[Devilstar2k2]

This was made using the method that you guys are talking about... Its a little choppy because it had to be built and painted within 2 days so my son could have it for Halloween. And yes, I know that its not accurate.

The foam sheets were cut then glued using a foam glue from the craft store (just a thicker kind of Elmers white glue. Then, some of the detail strips were added using a thick poster board.

Yes, the polyester resin ate the foam, but I used white foam (like a big dummy). I've read that polyester resin won't eat the blue/pink foams because its not a styrene... Not sure if thats true or not, but its what I've read.

I actually added the layer of Bondo on top of the fiberglass to get it smooth without sanding holes in the fiberglass sheets. Probably not the right way to do it, but like I said, it was a super rushed job and I had absolutely no clue what I was doing.

Overall, I don't think it came out too bad for the amount of time that went into it. The only thing that I don't like about it is that its not symetrical (the right bottom corner is angled), but thats my fault for not looking at as a whole before I went to the finishing stages.

 

[Honus]

Cool jet pack- I bet your son was happy!

Yes, the polyester resin ate the foam, but I used white foam (like a big dummy). I've read that polyester resin won't eat the blue/pink foams because its not a styrene... Not sure if thats true or not, but its what I've read.

Blue and pink foams (and some green) are polystyrene and polyester resin will melt them, as will acetone, kerosene, most spray paints, etc. Epoxy resin works just fine and will not harm the foam.

In the past I have done a sort of "lost foam" molding process. What I did was make my part out of blue foam and then covered it with clear packing tape. I then waxed the tape with a mold release wax. Then I cut some fiberglass cloth and used a spray adhesive to stick it in place on the taped foam. Next I wetted out the fiberglass with poyester resin, making sure to brush it into the fiberglass cloth. After the resin cured I melted out the foam with acetone, giving me a hollow fiberglass part.

 

[Dha Syntir]

I'm off to see if I can locate that book-thanks for the tip!

Yeah you pretty much got it. Fiberglassing is the easy part. Making the mold is a pain.

 

[tbone9600]

In the past I have done a sort of "lost foam" molding process. What I did was make my part out of blue foam and then covered it with clear packing tape. I then waxed the tape with a mold release wax. Then I cut some fiberglass cloth and used a spray adhesive to stick it in place on the taped foam. Next I wetted out the fiberglass with poyester resin, making sure to brush it into the fiberglass cloth. After the resin cured I melted out the foam with acetone, giving me a hollow fiberglass part.

Sorry to drag up an old topic, but... This is one of the neatest ideas I've ever seen. I've built all kinds of stuff from that kind of foam but never once thought about coating it with fiberglass and then melting the foam away. My wife is really gonna hate me now.

-Troy

 

[GrottyFurball]

I've seen people use fiberglass over the pink foam and it didn't eat it away.
http://www.culttvman.biz/phpbb2/viewtopic.php?t=6&postdays=0&postorder=asc&start=0

 

[drcrash]

RC modelers put fiberglass on foam all the time. They hot-wire cut wing cores, then fiberglass them, with some beautiful results. (If you like wings.)

They usually use epoxy resin, but some people use water-based polyurethane or acrylic floor sealer.

You can use polyester resin on styrofoam if you seal it with epoxy paint first.

By the way, the blue insulation foam is dow Styrofoam brand extruded polystyrene foam. The pink stuff is pretty much the same thing, but from Owens-Corning, and branded Foamular.

 

[GrottyFurball]

I heard that there's a difference with the blue and pink foam, I think the pink foam has something in it because when you work with it, it doesn't give you that skin crawling feeling.People have said the blue stuff does.

 

[CGClone]

I fly R/C planes as my other hobby. I build fuselages and wings out of the pink foam you buy at Home Depot. I buy it in the 1.5 inch thick and the fan folding for the profile/3D planes. I used a "D" battery-powered wire cutter with no problems.

Zap Finishing Resin (similar to an epoxy, mixes 1:1) does not melt the foam, works incredibly well with fiberglass. Has a bit of flex if you lay it on thin, otherwise its beautilly smooooooth.
http://zap.supergluecorp.com/pt40.html
You can get that at any local hobby shop.

I also use this on my foam creations for prop building:
http://www.smooth-on.com/shellshock.htm

You must work fast. When I say fast, Im talking like 2-3 minutes, so you work in small, small batches. It creates a rock hard plastic coating on the foam that can be sanded and shaped. Its somewhat vulnerable to heat like normal polyester resins, but this stuff is awesome. Very smooth surface as well.