Styrofoam prep?

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#1

Hello all.:slight_smile:

I’m wondering how to prep a styrofoam mold I made, so I can FG over it. I figure the resin will melt right through it quickly…

Could I bondo/sand/primer/sand it? Or latex paint etc?

I would prefer to be able to seperate the FG from the mold once cured, as there’s no angles that would prohibit release.

The styrofoam was bought at Michael’s arts and crafts store, and it’s not the type that is usually used for shipping. It’s a lower density(more brittle) than the stuff used for shipping…

Thanks for any info gentlemen.:smiley:

#2

I usually use Duratec primer over with bondo filler until smooth. Vice versa I think…

#3

BONDO is PER and can melt PS (polysytrene) foam too!

It is best to buy the PUR (polyurethane) foam from like Home Depot (go Tony) as then you have no problems then with melting.

Any water base paint could be used but it is too much work that can be destroyed quickly!

KYankton, is that primer a PER based or what?

#4

Come to think of it most of my foam R&D cores are a closed cell foam or one of the other 2 part foams that are probably not styrofoam. That stuff just about melts when you put down resin. You might be able to encase the original in the high stretch vacuum bag first and then mold over it.

#5

Tag, you it “K”…lol :smiley:

#6

Thanks for the info fellas…

I am trying a spray adhesive/aluminum foil method first, but if that doesn’t work, then i’ll try and find some PUR foam…

The only stuff I found at home depot before was the expanding foam(great stuff), which isn’t so great… LOL It likes to shrink…

Another question… Silmar 249/CF cloth won’t have any problems going over polyester resin/FG will it? I’ve never layered them before, it was always pure FG or pure CF work…

#7

epoxy and light fiberglass layer, then bondo and duratec.

#8

But why spend the time and extra money working with PS foam to save a few bucks instead of saving time, haertache and money on buying the PUR foam?

How big of a plug you working on and where are you located? If it is a small plug, stop by a local foam or mold shop and I’ll bet ya, they throw out good size pieces…I have found many local places to dumpster dive! In fact, we toss a fair amount of small pieces out (I’m a pack rat but…there’s a limit to it) but have a great donator in that field!

If you need to glue pieces together, Coastal Ent. in Orange, Ca. (lots of dealers that they sell too…) sells a special PUR expanding glues.

#9

Because all he asked for was how to do it, and no one answered his question. Styro for big plugs and ease of working with hotwire. You could also do a combo of styro and polyurethane. Glue the PU to the outside of the styro with epoxy.

#10

Thanks for the info guys…:slight_smile:

The mold is fairly small, about 11"x9"x7" or so… It’s for headlight housings, eliminating pop-up units so I can use BMW HID projectors and Hella 90mm high beam modules in place of the pop-up 7"x6" sealed beams…

I ended up spraying the mold with 3M super 77, and covering it with aluminum foil, then spraying PAM onto the foil(don’t laugh, it worked:D )… Problem was, it didn’t want to seperate, so I had to carefully break down the mold into four sections so I could glue it back together if needed… I think I had a few bad angles in the mold, because the FG came away from the aluminum foil beautifully once a couple sides were taken off…

Next step is to lay a couple more layers on the back side, and then overlay some CF cloth on the front.

I’ll end up picking up some PUR foam, duratec, PVA and some gelcoat for a hood project i’ll be redoing…

#11

Does it possible to cover pattern with aluminium adhesive tape see pic to prevent melting styrofoam.

#12

you could do it with two layers of masking tape and get the same results. Why waste the more expensive aluminum tape?

You realize that you will have to sand out the lines and deformities on your mold from the tape right?

#13

Hybridracers, that is exactally what I was trying to get across to them, spend the extra money for PUR foam and save yourself money & time in the long run of making the plug, mold and parts.

Time is money!

#14

Agreed

I wonder why everyone has the time to do something twice but not the time to do it right the first time.

Money?

If I have to spend 4 extra hours sanding a mold when I could have put an extra hour in the plug…Im not a smart business man and should probably think about not making anything.

I know I can earn more money in the time I would waste than its offset by buying the right stuff.

Couple sheets of PUR foam or 2 weeks of screwing up styrofoam?

#15

Styro is great especially for large plugs. What is wrong with using epoxy? Polyester, Bondo, Duratec, whatever will bond fine to it. Ever used a hotwire?

#16

Sorry not patternt I meant plug.

To cover plug with masking tape will prevent melting styrofoam.
Does it someone doing that with masking tape.
I cant find PUR foam in my town.

#17

What you thinking.

#18

What town or county / state are you?

Try Home Depot or Lowes as there insulation sheets, some are PUR foam.

#19

I am looking for PUR foam in my town but I cant find nowhere. So only solution for me is styrofoam. Can I make plug from styrofoam and cover with masking tape.

#20

yes you can…you are going to have to work three times as hard to surface your mold.

Id do what you have to, make the mold and pull a part out of it and then refinish that part and make a new mold of the primary part.

Its a lot of work but youre not leaving us with much for options.