Shape and Aerodynamics

I am not an aeronautical or automotive engineer, so take what follows with just a grain of salt.

At the velocities these cars travel, the only aerodynamic concern of any significance is drag due to the total frontal area of the car. Translated to English, that means that the car should be as thin as practical. The designs we have used are about 3/4" thick at the rear, to give room to bury the weights, and about 3/8" thick from the front to where the weights are located. The front edge of the car is cut square across its width, but is tapered to a knife edge, with the taper on the underside.

Why the tapered undercut on the front? Here is one of the innovations for which I will take credit. Pinewood Derby tracks generally use posts (dowels) which stick up in the center of each lane and form the "starting gates" for the cars. Some tracks (like our District tracks) have posts which pivot down toward the finish line and into slots in the centers of the lanes. Other tracks (like the one I built for our Pack) have posts which drop straight down into holes in the guide rails. In either case, a car which rests high against the starting post will leave the starting line a fraction of a second sooner than one which rests low against the post. Considering that races at the District level are decided by tenths of a millisecond, even a tiny bit of a head start is significant.

There is a limit to how "high" is "good". First of all, anything taller than the posts will try to slide up and over them and will be impossible to "spot" correctly at the starting line. Second, having the nose of the car higher works against the aerodynamic rule of making it as thin as possible. The cars in this web site rest against the starting posts about 3/4" above the track surface. In our Pack races, that's the limit, and I knew that from building the track and being in control of how much the starting posts project above the track. If you can, check the track(s) on which your car will run and adjust the nose height of your design accordingly.