The CD hovercraft is a tried-and-tested Make, but technological improvements have tended to be in the method of connecting the balloon to the CD. I have attempted to apply some of Sir Christopher Cockerell's original developmental research to this old favourite.
Step 1: Materials and Tools
In addition to the basic materials (an old CD, a balloon and a plastic bottle cap and hot glue), you will need a sheet of paper or light card, a thin sheet of expanded polystyrene, ordinary glue and a sharp knife.
The type of glue is not vitally important, since it will not be under any strain greater than the weight of the polystyrene and paper. If you use a water-based glue, though, try and be very sparing with it, as excess water will make the paper "cockle" and cut the vehicle's efficiency.