Let me start by saying Iíve done my share of body work, but I am neither a professional nor an expert, in fact I am quite the novice. I did my research and also talked with a friend that runs a body shop to make sure my plans made sense before starting my work. In the end the nature of the damage to my hard top may prevent the repair from lasting a life of being taken on and off, but itís about as good as it can get and I expect it to last many years. This stuff is messy to work with and proper personal protection equipment should be used.
I recently picked up a used hardtop for pretty cheap to run on my 07. The reason it was cheap is because it had been dropped. All the glass was fine but it had significant cracks at the corners of the rear window which is a pretty structurally important area. It also had some minor damage along the lower lip, purely aesthetic. The following photos show the damage, though only one side is shown there are equal cracks on both sides of the rear; the damage is bad enough you can pull the sides out far enough to stick your finger in the crack.
The first thing to note and the reason I decide to post this is that most people think this is fiberglass and can be repaired with traditional matting and resin. This is NOT true. The top is made of SMC. Fiberglass resin may work and it may hold up for smaller repairs but over time fiberglass and SMC will expand and contract at different rates and the repair will not last, not to mention you wonít get proper adhesion of the fiberglass to the SMC. I am sure there are exceptions to this.
The first thing I had to do was figure out how to reinforce the corners so the repair would last. We have to make it worse to make it better. What I chose to do was to sand down the damaged area feathering (dishing) that out so that it is thinnest at the damaged area and back to stock thickness elsewhere. This allows me to build up the repair material at the crack, but feather (dish) it out as much as possible for the best adhesion and strength. In addition to this I also made the crack into a hole so I could put a corner reinforcement inside. I cut corner reinforcements out of sheet metal and used a 3M panel bonding adhesive ( 3M 8115
) for metal to plastic bonding for the permanent hold. Because I could not get clamps on it I drilled and riveted it to hold the piece in place while the adhesive dried. The rivet heads will be sanded down later.
The next step is to repair the hole. The material I used for repairing this is 3M Automix Rigid Parts Repair
. Similar to the adhesive this requires a special gun that can push both sides up at the same time. I borrowed one from a friendís body shop, but you can also use a dowel or a screw driver to push them up in a pinch. Itís much easier when you can get to the backside of the area to be repaired but since I could not I was forced to build it up from the front. At this point I cut a piece of fiberglass matting bigger than the damaged area and coated it with the Rigid Parts Repair front and back and layed it over the hole and pressed it down with a spreader.
After this it is pretty easy. Just sand and fill and sand and fill until you build it back up. You can mix fiberglass strands in with the epoxy for strength too. I didnít do this on this repair but I did this on the lower corner as I built it up a little at a time. This stuff sands similar to any body filler.
Because I was going to be coating this top with a textured liner I was less worried about perfecting the body lines and tiny imperfections as I finished. In the end I finished with what you see above and these: