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How to add foam for reshaping a panel

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  • How to add foam for reshaping a panel

    Looking for suggestion on types of foam for adding onto an existing panel so I can reshape the panel. Also need suggestions on type of adhesive if the best solution is not a curing foam and had to be glued on. Once complete 5he new panel will be used as a buck for a mold.

    Last edited by AjzRide; 09-03-2020, 11:00 PM.

  • #2
    I did something like what you're asking about on a project many years ago. The build thread is here:

    I purchased the foam at Home Depot. It comes in varying thicknesses, has foil covering on both sides and is a golden tan color. It's sold as building insulation. The most important thing is that it's unaffected by fiberglass resin and thus won't melt like some other foams. I believe the pink colored foam also sold at Home Depot will not stand up to resin without a coating on it. You can buy similar and better foam for this purpose from fiberglass supply businesses, it's most likely going to be more expensive is all.

    I used hot melt glue as an adhesive.

    Please post pics and story once you get going on your project.
    Joel Heinke
    [SIZE=1][COLOR=#333333][FONT=&amp]Be original; don't be afraid of being bold![/FONT][/COLOR][/SIZE]


    • #3
      Thanks Joel, I'll go read your thread tonight.

      I've been using the pink foam for small projects so far, I just cover it with packing tape before I put epoxy on it to protect it from the resin, but that wouldn't work for making a nice mold. I have a build thread on the FFR forum, but I'll be happy to post some threads here on the more serious fiberglass modifications.

      I guess my only concern with the hot glue was how it would work if I sanded far enough to get to a glue spot, I guess I would probably have to dig that bit of glue out and add some filler to get that spot smooth.


      • #4
        Hey there,
        Sounds like a cool project, please post some stuff here.

        As for your question, I've actually used both the urethane foam sheets Joel mentioned, and two part foam (and canned foam too, I guess).
        I built a custom front fascia for my Fiero using the urethane sheets:
        I used hot melt glue and drywall screws to hold it together, and as you mentioned, if you hit glue, you pull it off and fix. I tried covering it in plaster first, but switched to Bondo body filler.

        For the two part foam, the key is to build a form around your panel to hold the foam while it expands, or it will just run all over.If your pouring on a vertical surface, you'll probably have to do it in multiple pours. I used this for the rear bumper on the 308 kit.

        The foam was from these guys:

        Again, post some pics and good luck.

        Bob custom '84 Fiero SE --->>> custom F408


        • #5
          Thanks for the advice Bob. I have already tried 2-part pour in foam once, and my attempts to make a good seal failed and it ran everywhere, taking a whole day to clean up

          I think for now I will stick with the glue on method and see how that goes.


          • #6
            Aj: When making plugs in the past, I have used the glue up method with "solid" sheets , the two part "pour" stuff, and the spray cans of triple expanding foam. All of them will work, but require different techniques for each to get the desired results.

            For the "home hobbyist"...I believe the spray cans of triple expanding foam are easiest to work with. [example]

            If you are using polyester resin, the polyurethane based foam won't "melt" when you put the resin to it. Using the spray foam, you don't necessarily have to build a "containment barrier", you can just build it up in "rows". Carve it down close to what you want, use bondo/filler to make it smooth and final shape, then glass over it.

            You can also use cardboard or something similar as a "base" to shoot the foam onto, instead of having to build up a layer at a time, if you have a large area/gap to fill. Just a suggestion.

            As I've said, I've used all three methods before, the OTC insulation foam (as long as it's polyurethane based, and you're using polyester resin) is the easiest, fastest, cheapest way to make/alter a panel from my personal experience.
            Good luck, whatever way you go!


            • #7
              Joel / Bob

              any tips on removing the foil cover of the poly foam boards? Looking like it’s going to take more than an hour per sheet to peel this stuff off in tiny shreds. A heat gun does not appear to help.


              • #8
                A coarse disc on an air grinder makes short work of it! Also makes a mess.


                • #9
                  I found that using the expanding spray foam is OK but you get varying densities in the resulting area you want to carve so can make more work for yourself using that. Small areas it works well in like filling cracks between other sheets or gaps but larger areas I wasn't that happy with it.

                  The foam Wayne used is roof insulation foam. It doesn't have the foil covering. It is rigid so needs to be carved to the shape of the panel but doesn't get eaten away by the resin. We can get it up in a local building box store but you should also be able to get from Home depot or Lowes down in the States. The foam carves very well. Like TDW says though it makes a mess.
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