Finishing STALKERV6 #29
The title of this page is a misnomer since these cars retain their status as "projects" as long as we have an interest in the car. But in spite of that law of kit cardom, this page will document the detailing and painting of #29. The car has been driven almost 300 miles and most of the kinks have been exorcised or rectified. Overall, the car has proven to be fun and reliable, and only minor tweaks to the suspension, steering, and engine tune have been necessary.
After seeing what was involved in maintaining a polished aircraft, I had decided that all the body panels on #29 would be painted for easy upkeep. But several other Stalkers have polished panels on their cars...and they really look good! I decided to try polishing the side and rear panels on #29 keeping in mind that if it didn't work out, the panels could always be painted later if desired.
I spent considerable time reading websites about polishing airplanes, cars, trucks, and travel trailers. All the sites shared comments about the labor and mess involved in polishing aluminum. When aluminum is polished, the removed material takes the form of a sticky, black, goo. Accompanying the goo is lots of black dust as the aluminum and buffer shed excess material. Many sites commented on the hundreds of hours necessary to polish a truck or travel trailer. Even though it was obvious that many had mastered the art of polishing metal, there was a great variety in the compounds and techniques used.
Stalker #29 is a simple car, constructed by a simple builder who believes simplicity is supreme, so I decided to try using materials with which I am familiar. During the course of painting my RV-6, I got very familiar with a dual action buffer and buffing compound. 3M manufacturers the finishing materials used in scores of auto paint shops and their Finesse-It compound was used on the plane. I suspected the Finesse-It would not be aggressive enough to work the aluminum so I found a local auto parts store that stocked 3M Perfect-It III Extra Cut rubbing compound. This compound is designed to be effective even after the "window" for buffing paint has closed. Modern paints can be very hard when fully cured so I hoped this compound would be aggressive enough to polish aluminum. Unfortunately the only size bottle the store stocked was the quart size which is enough compound to polish several Stalkers! The compound proved to be an excellent choice since it aggressively cut the aluminum but still yielded a glossy shine that required no additional finish work.
The aluminum on the Stalker is not AlClad which means more work is involved in polishing the panels. AlClad actually has a thin coating of pure aluminum which is mirror smooth and easily polishes. The panels on the Stalker have a machine finish which has a noticeable "grain". The other builders from whom I had seen comments sanded the grain from the panels before commencing the polishing. On the side and center rear panels I used a finishing sander and 400 grit wet-or-dry paper in an attempt to remove the grained finish. On the side panels I learned that it requires considerable care to take out the grain since it is difficult to visually determine the grain has been completely removed. In areas where the grain was not totally removed, a lot of extra polishing was necessary in order to get the surface consistent. Of course, most of the polishing time is spent removing the texture induced by the sanding operation.
If all the grain is removed, it is possible to achieve a mirror-like finish on the panels, but this requires a great deal of time and effort. The problem I had with the side and rear panel was getting a smooth finish over all the surface. Once the surface is brought down to a near-mirror gleam, every tiny imperfection is visible. Each builder must decide when enough is enough, and the panels are sufficiently shiny to be satisfactory. As can be seen on the photo above, I got a nice finish on the side panels, but it is not perfect. I finally decided, after many hours of work, that the panels were good enough for me.
A lamb's wool bonnet was used on an electric orbital buffer. I had used an air-driven buffer on the plane but decided to use the electric unit on the car so I wouldn't have to endure hours of hearing the whine of the air buffer and the rumble of the compressor. There is a lot of technique to using a buffer, and I no doubt failed to discover a great deal of it. Only small amounts of compound is necessary to cut the metal, but many, many applications of compound is necessary when trying to achieve a mirror surface. All the panels were removed from the car for buffing; I clamped them to a beefy sawhorse so they would stay put while I generated great amounts of black stuff as metal was slowly removed from the aluminum. I found the most effective method of buffing was to apply moderate force to one edge of the buffing wheel as it was slowly moved across the piece in increments of about one inch. After passing completely over a two square foot area, I repeated the process in a direction ninety degrees from the first step. Excess compound was wiped from the piece, more compound added, and the process repeated, and repeated, and repeated......
Can you tell any difference between the finish on the center panel and the two end panels? You may be able to see a slight difference in the quality of the reflections but I suspect that a non-builder would never see the difference. After seeing how difficult it was to get a consistent sanded surface on the flat panels, I was very concerned about sanding the rounded contours of the end panels. I decided to experiment and see what kind of finish could be achieved by skipping the sanding step. The end panels were buffed the same way as the other panels, but the grain was left intact. I was very, very pleased at how the grained surface developed a shine after a relatively short period of buffing. The finish is not like a mirror but is extremely glossy, and I am very satisfied at how it turned out. I wish I had made this discovery before beginning the job because I could have saved two days of work! I spent five hours on the rear center panel and am still not entirely pleased with the finish. Each corner panel was polished in less than one hour(!), and the finish is much more consistent even though it has a slight texture. I would be very pleased if all the panels were polished in this manner, but some builders may still prefer the mirror finish.
#29 is now ready for paint. The polished panels really added a finished look to the still unpainted car.
Painting the Stalker is unlike finishing most cars because the body components can be easily detached from the car. This makes the painting process more akin to a motorcyle and means we don't need as extensive a paint booth as normally used for car finishing.
My main concern was to prevent overspray from invading the shop. A simple tent was constructed from 3/4" PVC, lightweight plastic drop cloths, and duct tape. The whole thing costs less than $20.00. One side was kept open so overspray could exit outside the shop.
The paint finish I used was PPG Concept. This is a single stage, catalyzed polyurathane that contains a high ratio of solids and is very readily sanded and buffed during post-paint. One reason I didn't worry much about the unsophisticated spray booth was because I expected to sand and buff the paint. I found in previous projects that I just couldn't keep debris out of my backyard paint jobs and that it was easier to fix the problems later than to obsess over getting a flawless finish from the gun.
The fiberglass body components were wet sanded with 320 paper, and since the as-delivered finish on Brunton's kit glass is so good, only glazing putty was needed to repair the small blems in the gel coat. A single coat of PPG Omni epoxy primer was applied; this primer allows a three day window for topcoating without sanding. I did sand some areas where the primer was a little rough and did some additional work with the glazing putty. Well within the window, the topcoat was applied to the body parts.
Two medium coats of Concept was sprayed with a small gravity feed gun. After allowing the Concept to cure for two days, the paint was wet sanded with 1200 paper to remove all traces of orange peel, pollen, suicidal bugs and other nasties. This was followed by buffing with an electric buffer and 3M Finesse-It buffing compound. The compound quickly restores the gloss of the paint, and as long as enough paint was applied to prevent cutting through to the primer, the finish can be worked until it is mirror smooth.
The color is Trident Green, a Range Rover color. We wanted a "British Racing Green" that was not too dark. I had purchased yellow and white paint for trim around the nose ala Lotus along with a number roundel, but decided to go with a roadster look instead of a street-racer motif.
The rear deck cover is 1/2" birch plywood covered with fiberglass cloth and epoxy resin. The lid is the remnants of the un-used material for the engine side covers trimmed with 1/8" x 1/2" aluminum straps. The whole deal was polished and fastened to the ply lid with stainless screws. A cylinder lock completed the rear cover.
The cover incorporates a small storage box. Ample room was allowed for good access to the fuel filler cap. A prop rod was adapted from a unit found in the racing department of a hardware store.
Walmart automotive carpet was attached to 1/4" plywood with contact cement. The plywood was first sealed with epoxy resin so it wouldn't absorb water. The carpet/plywood units were dropped into place in the spaces between frame members.
After driving the car for awhile, it was evident the carpet was wearing quickly under the driver's heels. An aluminum scuff plate was fabricated and attached to the driver's side carpet with small screws in the area just aft of the pedals.
The transmission tunnel cover was covered with two layers of carbon fiber cloth wetted with clear epoxy resin. This complements the carbon fiber dash very nicely.
Several hundred road miles resulted in chips in the paint on the leading edges of the rear fenders. Since this situation would only get worse with time, I made stone guards out of 0.032" aluminum and pop-riveted them to the fenders.