With that, time for masking and spraying. Spent a day plus getting everything masked including the outside of the body completely covered. My experience with spraying undercoat using a Shutz style gun is that material goes everywhere. So a complete mask is pretty important. I also took the time to mask all the edges, so they’ll be painted rather than have undercoat. And there are a lot of edges on these two big pieces. I spread two big tarps on my driveway and sprayed toward the woods. Fortunately, the weather cooperated with reasonable temps, no rain, and no wind. Perfect. Using the one gallon U-POL Raptor kit, was able to get a full coverage coat on everything (Greg was following behind checking as I went), two coats on the cockpit roof, and three coats in the rear wheel wells. The front wheel wells already have the thick factory coating, so didn’t need additional coats. Also got three coats on the rear splash guards. That used every last bit of the one gallon kit. A few hours ago, pulled all the masking. It’s cured enough to touch. But needs at least 24 hours, so I’m walking away from it until Monday. Tried to get a few pics. Shadows in the garage prevent good pictures. But the coverage and color is very consistent. Couple small details plus time to cure, and these pieces will go back on the chassis for the very last time.
Also, the rear splash guards.
So some comments/observations about the U-POL Raptor product and the application. I spent a lot of time reading the directions, watching YouTube videos, etc. First, note this is a urethane 2-part catalyzed product, so in theory cures to a much harder finish than air dry water or solvent based products. Like Herculiner. Plus it’s possible to have a finer finish than those brush or roller applied products. But it’s definitely more work, a little more expensive, and highly recommended to use a respirator, gloves, and use the product carefully. Note also since it’s catalyzed, once mixed the material has a one hour pot life and will completely cure in about 24 hours. You would need to save unmixed components to have any for touchup or whatever.
The kit that I bought included the “free” standard Shutz gun. It worked fine and it’s handy how it screws directly onto the bottles of material. I read several bad reviews. But seems if you clean it after each bottle, it sprays consistently. I found this to be the case. After each bottle, just sprayed some reducer through it and went to the next bottle. This material and gun will always spray a textured finish. I was OK with that but wanted it relatively smooth. (Relatively being the key word here…) After reading other recommendations and doing a little testing, found that between 60-70 PSI and 15–18 inches distance gave the finish I was happy with. For the second coat of spray on the underside of the cockpit, we added about 1/2 ounce of reducer to the last 1/2 bottle of material. Then sprayed from a slightly further distance. This gave an even finer/smoother finish. Perfect for the second coat but maybe wouldn’t provide as good of coverage for a first coat. Late yesterday, I found that U-POL sells a higher end adjustable gun (UPL-UP4880) than can apparently give an even smoother finish. Wish I would have found out about that sooner because probably would have sprung for it. But couldn’t have it here soon enough to get the spray completed and my assembled car to paint on Oct 1. Maybe next time. U-POL also describes a process where with even more reducer and a more standard HVLP gun, you can get an even finer finish. Didn't pursue that, but another option.
I don’t consider myself an expert sprayer by any means. But I’ve done enough of it over the years to be mildly experienced. I found this product and the process to be relatively straightforward and not hard to apply. I think anyone following the directions could do the same. The finish is vastly better than the brushed-on water-based undercoat of #8674. But then again, for a Roadster, the underside is basically unseen. For the Coupe, not the case. No question it’s harder and in the long run probably more durable. Which may or may not matter as the material under #8674 is still fine after three seasons and thousands of miles. Would I use it again? Absolutely. Probably my first choice now. Where appearance isn’t as critical, U-POL does sell a brush/roll-on version. Also a urethane 2-part catalyzed material. For a Roadster build, that’s something I’d seriously consider while avoiding the time and effort for spray masking.
That's it. Next week everything goes back together and ready for the painter the following week.