Body Work: Prepping & Priming the Rear Clip
In the last update some of the final touches on the body work were completed in preparation for applying primer. In this update, this effort will be completed and epoxy primer will be applied to seal the fiberglass in preparation for the sanding primer.
One of the first items to tackle was shaving the rear antenna. After giving it a fair bit of thought I decided I’d prefer the clean lines of the rear deck without the antenna in place.
So here’s what I started with – the stock antenna mounted right above the rear fender. I removed the antenna and got to work dishing out the fiberglass in the area around the hole with a die grinder.
After the grinding was completed on the top side the surface was thoroughly cleaned prior to application of the fiberglass and resin.
Once the top side was repaired the process was repeated on the underside to create a full depth structural repair of the panel.
And here’s how it ended up following the application of several layers of fiberglass, sanding, and then filling the remaining imperfections with body filler. All told this took about a weekend to complete (including down time waiting for the resin and body filler to cure).
If you’re interested in learning more about the process I followed to shave the antenna check out the how-to video below, it includes a lot more detail and information.
With the antenna hole taken care of the rear clip was ready for primer. In the last few updates I took care of the body panel replacements and miscellaneous body work to prep the panel for painting. I also block sanded the entire rear clip with 180 grit sandpaper to blend in any deep scratches created by the 80 grit sandpaper used during the rough body work.
Now that the sanding was complete I blew the body clean with compressed air, gave it a quick once over with a water based wax and grease remover, and set to work taping off the rear clip. I didn’t want to get overspray anywhere so I was careful to get the taping done neatly and cleanly with no holes or gaps.
I started by taping around the inside of the fenders with painters tape, creating a margin about two inches wide.
With the tape in place pieces of painters paper were cut and then taped into place. The painters paper works much better than newspaper because it’s much less prone to bleed-through. It can be bought at your local home improvement store and comes in roles of various widths.
In the photo below you can see how the method I used provides good access for painting the inner edges of the wheel well. Once the fender was completely covered I taped the paper to the floor as a safeguard against overspray
And here’s the rear clip fully taped off and ready for primer. I was certainly looking forward to having it all one color again! I was also anxious to see how my body work came out. I’ll admit I was pretty nervous that the body seams, especially those between the rear deck and the fenders, would be wavy.
With the entire car taped off it was given a thorough cleaning using a water based wax and grease remover. Personally, I prefer water based cleaners since they evaporate much more slowly and are easier to work with. To minimize the potential for fisheye I wiped the entire car down three times with a thoroughly wetted paper towel, turning the paper towel often and then replacing it once all sides were used. If this was in preparation for base coat or clear coat I’d use a lint free cloth. However, given that this is just for sealing primer, the thought a stray lint fiber here or there wasn’t a big concern for me.
For the purpose of this photo I wasn’t wearing any gloves but, if you’re doing the entire car, the use of latex or nitrile gloves is necessary. Make sure you have some!
Once the body was cleaned I started setting up to spray primer. Before I go any further a brief explanation into my thought process is probably necessary. My approach to painting the car will follow a multi-step approach. This first application of epoxy primer is intended to seal the fiberglass. In many places I sanded through the gel coat of the fiberglass panels exposing the individual fiberglass fibers. The epoxy primer will seal those fibers and provide a good base for the subsequent sanding primer, base coat and clear coat layers.After a fair bit of research I decided to go with Southern Polyurethanes epoxy primer. It comes highly recommended across many online automotive forums, it’s relatively easy to use, it’s fairly forgiving to work with (you don’t need a $500 spray gun), and it’s reasonably priced. The biggest challenge was the required application temperature. The material I used needs to be used when it’s going to be at least 60 degrees during application, and for 24 hours after application.
The primer also comes in multiple colors. I chose white to match the front clip (which won’t be primed – it doesn’t need it) and to provide a contrasting color to spray the gray sanding primer over.
After carefully measuring out the base and activator the two parts were mixed together and stirred very, very thoroughly.
Also, once the two parts are mixed you need to give the paint a chance to catalyze before spraying it. This waiting period is called an induction period. In the case of the Southern Polyurethanes primer the induction period was a minimum of 30 minutes.
After the induction period was finished the primer was given one more good stir, the paint gun was loaded and I put on my safety gear.
When using all epoxy primers it’s important to know that the use of personal protection equipment is really important. Per the manufacturer’s material safety data sheet (MSDS) they recommend using a supplied air hood to avoid breathing in any fumes or harmful chemicals such as isocynates. In my case I do very little spraying and, when I do, all the windows and doors are open to provide good ventilation and I have a fan running to increase air circulation. In light of this I opt to use a high quality, tight fitting respirator with fresh filters.
I didn’t remember to get any photos of the initial painting but here’s how it looked after getting two wet coats of primer onto the car.
The nice thing about the Southern Polyurethane epoxy primer is that it has a semi-gloss finish that allows you to see imperfections in the paint pretty easily. Despite my best efforts there were two small areas of fish eye. Once the paint cured those areas were wiped down with cleaner, sanded and then wiped down several more times.
In addition to the small areas of fish eye there were several spots where minor body imperfections were visible. This really caught me by surprise because I could have sworn I caught them all. Ultimately, I concluded it’s just really hard to see imperfections like this on a bare fiberglass panel.
Once I identified the surface imperfections I taped them off and applied a very thin coat of body filler, sanded the filler down, removed the tape and then block sanded the entire rear clip to accept a second coat of primer. The primer worked very well for me but one down side is that you only have one week to apply a second coat. Any longer and you have to scuff the surface before painting over it. Since the content of this update was completed over the course of several weekends I was stuck completing the extra sanding.
After lots of block sanding here’s what the rear clip looked like. It seemed like a lot more paint got sanded off than I expected but my primary goal has always been to have straight panels without surface imperfections.
It was eye opening to see how many spots I had missed in my first pass through on the rear clip. It was definitely a lot easier to see the imperfections with the primer on the car so I took the opportunity to dial in the body work as good as I could before putting down the next coat of sealer/primer.
After sanding, cleaning and then cleaning again, I put down a final application of epoxy primer. Similar to the first application two wet coats were applied.
And here it is, the primed rear clip ready for the application of high-build sanding primer. Overall, after fixing all the little imperfections, I was really pleased with how it came out. I gave the body a really good once over while the paint was still wet and glossy and I was impressed with my rookie body work skills.
Here’s a photo of the area I was most concerned with – the panel joint between the rear deck and fender. I was real pleased with the fact that this seam came out nice and even without a lot of “waviness”. It just goes to show that using a proper block sanding approach can lead to good results – even if your a beginner.
Well, that’s it for this update. I’m going to continue the process of getting the car to the point where I can ship it off to the body shop so stay tuned for more updates!If you have any questions about this update, or a project you’re working on, I encourage you to visit the Corvette Restoration Forum and ask your question! I’m there fairly often and, together with the other great forum members, you’re sure to get some great advice and feedback.