Pinewood Derby Stories and Photos from Maximum Velocity
Looking Good: Techniques for Finishing Your Car By Randy Davis
(An update of an article originally published January 8, 2003)
Have you seen a car on the staging table that caused your jaw to drop from admiration? The paint job looks like it came right out of a custom body shop, and other details like decals and accessories look fabulous. You ask yourself: "How did they do that?"
I won't kid you - I oftentimes ask that question as well. Clearly, some folks know how to take the finish work to a level beyond most of us. However, I can share with you some basic techniques for putting a nice finish on your car. The main tasks to be addressed are filling, sanding, priming, painting, and decal work.
FILLING It is very difficult to create a car of any intricacy without a gouge or nick that is too deep to sand out. For small defects, the simple cure is wood putty (or "Bondo" - a car body filler). Press enough of the product into the defect to completely fill the defect with some excess. If desired, you can smooth the putty with a finger dipped in tap water. Allow the putty to dry thoroughly. If the putty sinks or cracks, apply more putty and let it dry again.
For large defects (e.g., a hole drilled the wrong place), cut a piece of wood to fill as much of the defect as possible and glue it in place. After it dries fill any remaining voids with putty, and let it dry.
Next, it is time to proceed to ...
SANDING As you probably know, sanding involves smoothing the car, starting with a coarse grit paper and progressing towards a fine grit paper. A good grit progression is 60, 120, 240, and 400. This can of coarse vary, but the ultimate goal is to create a very smooth finish, free of defects and scratches.
Sanding flat surfaces is greatly simplified by using a sanding block. A sanding block is designed to hold 1/4 of a sheet of standard sandpaper. It has a padded surface which helps make the finish very smooth. When selecting a sanding block, try to find one that can be easily held by your child (not too wide or heavy).
Figure 1 - Sanding Block
For sanding concave (inward curving) shapes wrap some sandpaper around a piece of wood (or your finger). A dowel rod or a piece of broom stick works well for sanding concave curves.
Figure 2 - Concave Curves
Figure 3 - Convex Curves
For convex (outward curving) shapes, use a sanding block, or just hold the paper in your hand and use fingertip pressure to sand the desired area.
After the sanding is complete, remove all dust with a vacuum and/or soft rag. Then create a handle for painting. Two alternatives include:
- Inserting a dowel rod into a weight hole
- Inserting a long wood/dry wall screw into the bottom of the car - you might be able to insert the screw into a weight hole so that the screw hole doesn't show, but be careful to not go all the way through the car.
Next, I recommend masking off the axle slots (if you have axle holes, then insert round toothpicks into the holes. This makes future axle insertion much easier.
PAINTING - PRIMING Before priming, locate a place for the car to dry. We have a piece of wire strung under a shelf in the shop, with some binder clips attached to the line. When we use a screw as a paint handle, the binder clip can be clipped to the screw, allowing the car to hang upside down to dry. If you use a dowel rod as a handle, drill an appropriate sized hole in a workbench, or in a heavy piece of wood. The dowel can then be fitted into the hole while the car dries.
When spray painting, make sure to wear eye protection and a breathing mask. Then cover the hand that will hold the car with a plastic bag, secured with a rubber band. Paint in a well-ventilated, dust and wind free location. Also watch out that the over spray doesn't get on something important (cars, walls, etc.). We have large plastic garbage cans, so we flip up the lid and use it as a backdrop for painting. Optionally, a large box can be set on end to serve as a backdrop.
The selection of the type of primer is important. I have had the most success with a "high-build" or "filler-primer", such as that offered by "Rust-Oleum" and sold at auto parts stores. This type of primer tends to fill in the pores of the wood, minimizing the number of primer coats required. If the sanding job is done well, generally three to four coats are sufficient.
When spraying the primer, keep the can moving and apply light coats. If you go too heavy, you will get runs that must be sanded out.
Let each primer coat dry, then sand with 600 grit paper and recoat. If you find a spot that doesn't fill in well, you can apply a little wood filler or Bondo, sand, and continue priming. Once the car body is completely smooth, you can proceed to applying the color.
PAINTING - COLOR There are many types and brands of spray paint. I strongly recommend acrylic lacquer paint such as "Dupli-Color - Perfect Match" (auto parts store item). This type of paint dries quickly, and can be recoated at any time. Watch out for brands that "can be recoated within 1 hour or after 24 hours". What happens if you recoat after, say, three hours? Trust me on this one, you don't want to know.
I also suggest avoiding enamel paints. Enamel paints generally take a long time (many days) to cure, are very susceptible to finger prints, and act like a graphite magnet.
Generally two or three color coats will be sufficient. After the last coat allow the car to dry thoroughly. Then proceed to adding decals, pin striping, etc., and finally apply clear coats.
DECORATIONS Decorations are certainly not required, but that can really dress up a car. They also have a practical use; they can cover up any defects in the paint job. We'll discuss dry transfer decals, stick-on decals (includes stickers) and pin-striping. All of these products are available at Maximum Velocity. http://www.maximum-velocity.com/decals_etc.htm.
Dry-Transfer decals are available in lots of designs, many of which are targeted at pinewood derby car builders.
Figure 4 - Dry Transfer Decal
The best dry-transfer decals are very thin and do not have a clear edge. Thus, they blend in to the paint such that you have to look closely to see that the design is actually a decal.
To apply dry-transfer decals, cut out the desired design, place it on the car in the desired location, hold it down, and use a soft pencil with a rounded tip to scribble over the entire decal (you will actually be scribbling on the transfer material, not the actual decal). After scribbling over the entire decal, carefully lift up on the transfer material. If the decal is not completely detached from the transfer material, scribble some more and try again. After the transfer material is removed, take the provided tissue-like paper and rub it over the entire decal.
Stick-on decals, as well as stickers are also good choices. These apply much easier than dry-transfer decals, but make sure you put it where you want it. As you know, stickers like to attach themselves where you don't want them!
Figure 5 - Sticker Decal
My daughter used stickers to decorate her Diamondbacks car; she found the stickers at a team shop. I believe that team stickers exist for every professional team, as well as most college teams.
Figure 6 - D-Backs Car
Home Made Stickers
Can't find what you want, or on a budget? Make your own stickers! Find a photo, a logo, or most anything on paper. Cut it out, apply some glue, and place it on the car. We used a Hershey's chocolate bar wrapper to decorate this regatta boat.
Figure 7 - Homemade Sticker
Pin Striping I am a big fan of pin striping; it is relatively inexpensive, easy to apply, and can really dress up a car. Pin striping is long, thin, colored tape that has an adhesive backing. It adapts well to curves in the car and can be mixed and matched, both in color and in width.
Figure 8 - Yellow Pin Striping (1/4 and 1/8 inch)
To apply pin striping, unroll a piece longer than you need, pull it taut and then apply it to the car. Use a piece of tissue paper (not Kleenex, but the kind used in gift bags) to press down on the pin striping. This will eliminate any air bubbles and ensures that it is pressed down well. After the pin striping is in place, trim the excess off the ends with a sharp knife (hobby knife or razor knife). If the pin striping will be placed on the front and/or back of the car (as in Figure 7), wrap the pin striping under the car and trim it off underneath. This makes for a much cleaner finish.
FINISH COAT All decorated? Now it is time to protect your investment and give a deep glossy look. Applying multiple clear coats will not only improve the appearance, but will (mostly) protect the car from finger prints, graphite and minor scratches. Make sure to select a clear coat that is compatible with the paint you used. If you used Dupli-Color for the color, then use Dupli-Color Clear Coat. I recommend at least five coats of clear. Fortunately it dries very quickly, so you can apply the coats in a fairly short period of time.
CONCLUSION I have barely covered this subject as there are certainly other options for painting and decorating your car. If you have a technique you would like to share, please send it to me, and I'll try to include a number of reader ideas in a future article.