interior plastic modification help

[eaglzcirca33]

Hey fellas, I need some help in regards to the interior of my car. I have a 1970 Camaro I'm in the process of pro touring. The lower plastic interior pieces up front where the vents are located is what I want to modify. I would like to eliminate the vents and vent levers(I have new classic air). I want to turn the vents into speakers which will be easy but with the vent levers removed, it leaves holes that I want to eliminate(fill in). Does anyone have any suggestions on how to prep these pieces that will allow me to cover these holes up? I'm new with fiberglassing and plan on doing some fiberglassing custom work inside the car but does fiberglass stick to plastic or does anyone have any other suggestions? Thanks

[BulldawgMusclecars]

If I'm understanding correctly, you basically want to install kick panel speakers in the existing holes, and cover up any other holes in the plastic? The easiest way to do this would be to figure how much spacing you need for the speaker, and glue MDF speaker rings (available from a stereo shop, online, or make your own) to the plastic with epoxy. You can then stretch some old t-shirt material over it, and glue it down with 3M Super Spray Trim Adhesive. Once it sets up, paint it with fiberglass resin. It may take several coats, with drying time in between, but eventually you will have a sculpted-looking panel that is hard enough to sand. You could sand it, fill (with standard plastic filler, like Bondo or Rage), and paint it if you wish, or coat the back of a piece of stretchy, automotive grade vinyl/leather with the same 3M adhesive and stretch it over the panel. Hold it in place with small clamps, or even clothes pins will work well, and let it dry. Sometimes it helps to heat the vinyl a bit with a heat gun. Once its done, cut your speaker opening in the vinyl, install the speaker and trim ring, and its done. I'll upload some pics of an example I did, if I can find them.

[sniper]

With all due respect, there are a few problems with the advice above. First is that fiberglass resin will not adhere to plastic. Second, is that he made no mention of using actual fiberglass. Resin by itself over cloth is weak and will get smashed in with the slightest taps of the foot. The fiberglass will give the kick panel strength, but if not careful too much heat while curing will warp the panels. But you must use glass. The first layer of material, needs only a wet out of resin.

Anytime I do any fiberglass over plastic, I first properly prep the piece and use an adhesion promoter then paint it with epoxy primer. Resin will bite to that primer. But you must have a great bond of primer to plastic. I also drill holes throughout the plastic to create a mechanical adhesion as well.
You can glue the rings with simple hot glue. Tape off the inside part of the rings to make shape up easier, with little to no resin getting on the inside of the ring. Don't add to much bulk to the edges especially near the door jamb. You can simply add a layer of glass on the outside, then from the inside or rear of panel add more glass to the back of the face of the panel. Adding your build upon the inside. This will also reduce finish time on the outside.

There is certainly more than one way to skin a cat, but having done more than a few customs fiberglass pieces, I can assure you those extra steps will be rewarded.

[eaglzcirca33]

Thanks fellas, I really appreciate the advice.

[BulldawgMusclecars]

I have only done the set above (don't usually do stereo work), but I guess I got lucky, since the material wrapped around the plastic and was glued, so that the resin didn't actually make the bond to the panel...the glue did. The resin only reinforced it. After several coats of resin, as I mentioned, and a light application of filler, the panels were hard as a rock and would not be easily dented. Your advice makes sense, though, and I'll incorporate that next time I do a project like this.