The group of four Co-Hog Restoration Porsches from the 1980's is nearing completion. They were started last November and have been progressing along with numerous other Co-Hog projects. Two will be white, one is being done in a Martini Racing livery and one will be for me and I keep changing my mind on color and options.
To see/read the story from the beginning check out the first two progress reports. Part 1 and Part 2 give plenty of details about what it’s taking to restore these Co-Hogs to better than new.
The Martini Racing version now has all of its graphics applied and it’s ready for 2-3 coats of 2K clear coat to seal in the delicate striping and prevent lifting during handling. The two white pieces will have their clear coat applied first and the graphics afterwards. The fourth one is still being brought up to this level of finish after serving as the Martini prototype until now.
The Martini livery application starts with preparing the variety of stripes needed. The body center, the side pods, the top of the rear fenders and the rear panel require different widths of the same pattern. The stripes are shown as completed.
The windows and other details are cut from 4 mil (0.1 mm) flat black and colored vinyl. One of the side windows has been cut using the clear acrylic template.
The number 38 (barely visible in front of the passenger side) has special personal meaning for the new owner and was created from my custom artwork by a friend using a vinyl cutting machine.
To work out my technique I started with the widest stripe.
Here all seven individual stripes have been cut and aligned into a single unit - ready for final cutting to the appropriate lengths before application.
It took several weeks of on and off trials and then multiple final sessions for each finished stripe. In the end, I started each one with the red stripe on the background midnight blue color. Spacers of midnight blue were then added before applying the wicked finicky lighter blue stripes. The completed center stripe is 0.945” (24 mm) wide.
The stripe sections for the side pods are the narrowest. The entire stripe is only 0.45" (11.4 mm) wide. Spaces between the light blue stripes are 0.025" (0.6 mm) and the red stripe is a whopping 0.0370" (0.9 mm).
Now the windows and most of the body graphics have been added. Each piece is cut, and hand fitted to the individual body.
Side windows are the trickiest. I made an acrylic template which I position with spots of double-sided tape and then carefully trim around. Final touch ups are always required and are done by eye.
Engine bay details on the whole group were built up from more blocks of vinyl. The exhausts were done with arch punches, the blue tools in the upper right corner. One layer is silver and then one on top using flat black.
Each set of finish coats (sealer, primer, color sealer, color and 2K clear) was applied with an airbrush or mini-spray gun. Sealer and primer are solvent-based, color sealer and color are water-based and the 2K clear is solvent-based.
The brand of the final layer of 2K clear coat was determined by continuously testing new brands on properly prepared blanks. Clear coat manufacturers make a variety of formulations for multiple markets. Slight chemical differences result in a wide variety of spraying behavior, thinning options, nominal thickness, expected level of orange peel and even color. The two white cars were finished with a US made 2K clear and the Martini car was done with an Australian brand.
Years of testing and spraying has yielded a wealth of knowledge that all goes out the window when the spraying starts. Then it becomes whatever works wins. The results are then added to the pile of experience.
When spray painting the weather is the biggest factor. Correct compensation for the temperature and humidity is the difference between nicely done and a horrible mess. Needless to say my spray booth is not temperature and humidity controlled.
Without a totally controlled environment, determining the proper mix, spray pressure and airbrush/spray gun settings to give the best flow out and gloss is slightly different for just about every weather condition. I use these various test forms to nail down the variables before actually painting anything.
If you think of spraying paint as trying to apply a steady even stream of balls of paint into a box it's easy to visualize how complicated the bouncing balls get when sprayed into a corner or crevice compared with a larger and flatter surface. A good spray gun will give a good, consistent stream of similarly sized balls that hit the surface and spread out together. The balls on the outer edges of the spray cone will always be smaller and drier - leading to overspray which is sandy and doesn't flow out. Keeping things wet as you progress becomes critical for a good gloss.
To get the best finishes I often use the airbrush for the corners and details and then a mini-spray gun for the overall finish.
When doing the finish coat on a piece that has taken so long to create it can get quite tense. I do envy the automotive painters who have the latest spray booths, the best equipment, a consistent stream of painting to do and the experience to make it all work. Their work is amazing.
My own home built spray booth is nearing completion and progress will be shown in an upcoming post. It has actually worked quite well to improve the quality of my spraying.
Of course, stay tuned for more on the Co-Hog Restoration Porsches.
Check out the rest of the restoration posts with these links: