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  • Working with Foam

    Okay... i've gotten enough interest from various people about this that I figured I'd post a tutorial and perhaps spur some creativity... turn on some light bulbs... etc. 56K users beware.

    Here goes: One way to make a radio/screen trim bezel for your funky-shaped dash:

    Steps 1-3:

    The foam is Renshape 5025 from www.freemansupply.com. It's hand-workable, dimensionally stable, chemical and solvent resistant. You can get it in several densities to meet certain mechanical requirements, but I generally go with 15lb because it holds a nice edge but is still easy to sand.

    The rule here is cut more than you need and work down. It's easy to cut away material, but hard to add on. I shaped a block of it to fit into the dash opening, then measured the dimensions of my screen, plus tolerance which i made to be about .125" overal side to side. It was very close up and down with the sliding screen mechanism... to within a millimeter. It took some finessing to get right. Once I got it here, i traced the edge of the dash opening onto the foam so i had a guide.
    Attached Files
    Et ipsa scientia potestas est.

    Worklog for my 2007 Civic Si ...f*** it...
    Pictures of the Corolla (retired)here
    Need to make something? Here are a few ideas.

  • #2
    The next step is to follow those guides. Starting with about 80-grit paper wrapped around a foam-rubber sanding block for the convex portions, and around a piece of 1" PVC or other tubing for the concave portions, i get the basic shape sanded out. I go all the way up to 400 grit. This levels the surface considerably and leaves very little filling to be done before primer.
    Attached Files
    Et ipsa scientia potestas est.

    Worklog for my 2007 Civic Si ...f*** it...
    Pictures of the Corolla (retired)here
    Need to make something? Here are a few ideas.

    Comment


    • #3
      As I'm doing this, I'm constantly checking for three things. Fit, fit, and fit. I'm finessing the curves so that my gap is uniform around the edge, I'm making sure the trim isn't standing proud of the dash opening, or sitting inside it. and above all, if you've got moving parts, i'm making sure those aren't catching. This part is very lightweight right now, so if something touches it, you'll know it.

      once the fit is good, you can finish however you like, but I'll go through the steps of painting it.

      Here is a quick view of all the products I used in finishing. These should be available at your local auto body store. Bulldog Adhesion promoter works well if you're using the foam to amend to an existing ABS piece or something that typically suffers from paint adhesion problems.

      These pics show the bezel after a coat of automotive 2K type primer. I was lazy and didn't bother here, but you can actually save yourself a tiny bit of sanding by burnishing some spackling compound into the foam before primer to fill the tiny holes in the foam. Either way, I wet sand to 600 grit before paint.
      Attached Files
      Et ipsa scientia potestas est.

      Worklog for my 2007 Civic Si ...f*** it...
      Pictures of the Corolla (retired)here
      Need to make something? Here are a few ideas.

      Comment


      • #4
        Lastly, I spray on my basecoat and clearcoat. As I mentioned before, the foam will not melt from polyester resins, acetone, lacquer thinner... the whole mess, so you can use whatever finish you like. The most important part is filling and priming... but once you get it smooth to your liking, you can use rattle cans from the HW store if you want.

        But after it's all cured, said and done, I glue the bezel into the dash opening and voila. Professional looking trim for that funky dash that Scosche and Crutchfield don't make kits for.

        Hope this proves helpful.
        Attached Files
        Et ipsa scientia potestas est.

        Worklog for my 2007 Civic Si ...f*** it...
        Pictures of the Corolla (retired)here
        Need to make something? Here are a few ideas.

        Comment


        • #5
          In closing, let me just say that there are a million ways to skin this cat. You can laminate fiberglass or CF over thinner areas to provide reinforcement, you can glue or shape this over factory pieces so you can carve/drill out places for buttons, switches... you name it. If anyone has more questions, I'll be happy to answer.
          Et ipsa scientia potestas est.

          Worklog for my 2007 Civic Si ...f*** it...
          Pictures of the Corolla (retired)here
          Need to make something? Here are a few ideas.

          Comment


          • #6
            Wow that really looks like a good way to go, thanks for the info. I am a bit confused on what you did for finishing it. After it was sanded, and I'm assuming this stuff is rather easy to sand, dent, etc (looks slightly like florist foam) all you did was paint it? Wouldn't it still be easly dented etc without a coating of fiberglass or something?

            Comment


            • #7
              nice work thanks for posting!

              Comment


              • #8
                ...

                Watching this thread. Very interesting!

                John
                Action figures sold separately

                Comment


                • #9
                  this good sir, is pro

                  positive rep to you!

                  Comment


                  • #10
                    As far as it's workability, it can be dented, but there are things in the finish that improve that dramatically. Even using a few coats of decent urethane clearcoat improve the surface hardness enough that the usual poke of the finger or the like will not damage it. Compared to floral foam though, this stuff is like granite.

                    I've also brushed on epoxy resin before and hit it with a little heat to get it to saturate the pores, then sanded smooth. That helps improve the surface too.

                    here is another instance of foam with different finishes.

                    http://www.mp3car.com/vbulletin/showthread.php?t=82098

                    i've done one surface flat black, laminated CF to the top of the cup, then the same primer and paint as the bezel for the knob. So you can imagine that part gets constant handling and i've had zero issues.
                    Et ipsa scientia potestas est.

                    Worklog for my 2007 Civic Si ...f*** it...
                    Pictures of the Corolla (retired)here
                    Need to make something? Here are a few ideas.

                    Comment


                    • #11
                      your result is very nice - I must say. It [I]looks[I] like a well made quality part.

                      The foam you're using, however, is used to make plugs for molds and is not meant to be used in a structural way whatsoever. I'm quite surprised you managed to keep it in one peice, your skills with it must be great. What I am saying is that your part should be made of something with at least a bit of structural strength and stiffness. I'd say you've made an excellent prototype for your product. Thats a good use of this foam, prototyping, but not for the actual part.

                      Essentially you've used a foam plug to make a mold out of bondo and paint. Your paint is cured so now it is the structure of the part. Too bad you didn't use some kind of mold release on the foam, since you could seperate your 'shell' and use it as a mold for an actual strong part, made of plastic or fiberglass.

                      I dont mean to say you did it wrong, I just mean to say you aren't using the products in the standardized way that they are intended to be used for good results. It just so happens you got good results anyways... just be careful you dont drop it. Correct me if im wrong and you did infact use some kind of a structural layer other than the bondo.

                      The paintwork looks fantastic. Did you match it to the exterior finish of the car? Did you do it yourself?

                      Comment


                      • #12
                        Vinister, you're right about the standard use of the foam. I will say that not all foams are created equal. There are far lighter foams like 2 and 5 lb which offer no real structure beyond the shape that they hold. I usually use 15 and 20lb foams which get to be like working a piece of balsa.

                        Regarding it's use, I agree that it should not be used as a load bearing part. A trim bezel however is rather far from it. I've made other variations of the bezel including one that incorporates a few plies of carbon fiber on the lower portion which makes the whole piece (unreinforced otherwise) more rigid than the ABS part that came on the car... but there is no bondo on the part. it's just foam/primer/bc/cc. I am experimenting further with creating a silicone rubber mold based on this and using polyurethane resins to create multiple parts... so to say, using the foam for that which it was intended.

                        i did do the paint myself. I went and had a lady at the paint store match my two interior tones for me. Provided you take care not to contaminate your paints with anything, it's actually quite easy to get that finish. No wetsanding or buffing was needed there.
                        Et ipsa scientia potestas est.

                        Worklog for my 2007 Civic Si ...f*** it...
                        Pictures of the Corolla (retired)here
                        Need to make something? Here are a few ideas.

                        Comment


                        • #13
                          wow thats tits. thank you sooo much for posting this. i was tryign to think of a way to make a decent lip for my screen but i could imagine making somethign with fiberglass for mset up it would be a crazy little shape that although small in size would be crazy difficult to make it look half decent) and bondo was out f the question. thats soooo hot man. wouldnt fiberglass resin melt the foam though?
                          http://i25.photobucket.com/albums/c8.../positions.gif

                          Comment


                          • #14
                            Renshape is essentially polyurethane that was aerated to give it a certain density. Urethanes don't contain styrene like EPS (pink foam at home depot) so it will not dissolve in the presence of styrene monomer as is found in polyester resins. If you are using a styrene foam, you can also use epoxy resins which don't melt styrene foams.
                            Et ipsa scientia potestas est.

                            Worklog for my 2007 Civic Si ...f*** it...
                            Pictures of the Corolla (retired)here
                            Need to make something? Here are a few ideas.

                            Comment


                            • #15
                              no the foam is resistant to almost any chemicals and heat, including fiberglass resins and the like.

                              I could see it looks a little stiffer and denser than most stuff i've seen or worked with. The results are great anyways, so that's that!

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