Remember the CO2 cars you made in middle school. This is basicly that with a model rocket engine. And built more stable.

Video will explain...
http://www.youtube.com/watch?v=8gvEG2-P6e0

Step 1: Building Car

When you build the car keep in mind that you want to have enough downward force to keep it on the ground. I recommend using balsa wood. I had a extra from my tech teacher who got fired. You need to install 2 screw eyes in the bottom for the guide wire. I made the fin and spoiler out of extra wood and dowels drilled into the car. Be creative and make sure it is gona stay on the track and not free flight(unless you want to) You all so need a hole in the back for the rocket. A "A" sized rocket will fit in regular dragsters with a a little tape nearly perfectly.

Step 2: Paint

If your bored paint. i painted it white with spray paint. Next some tape then did a coat of black. I then cleaned it up with black and blue sharpy.

Step 3: Launching

For my set up i had 2 bricks on either side with fishing line tied in between. I had a boat cushion on one end. Insert the engine with igniters in one end and use a regular model rocket starter. Mine went pretty fast and work twice till it burned the fishing line the third time and swerved into a wall.

I think its easier to understand in the video because its not to difficult.