A (geeky) secret sewing project recently resulted in an empty spool of thread.
"What to do with an empty spool?" mused Auntie Janice. Clearly we needed to make a balloon hovercraft. The balloon's air pushes on the floor to create an air cushion, reducing the friction against the CD and making it go Faaast!
One empty spool of thread
One old CD
Glue gun or Blu-Tack
Glue the spool of thread to the CD, such that the hole in the spool of thread is aligned with the center hole of the CD. Make sure that any extra holes in the spool of thread are blocked; there should just be a solid tube.
Inflate the balloon, then attach the balloon to the other end of the spool of thread (this is easiest to do if you twist the bottom of the balloon to prevent the air from rushing out). With a little practice, you can reinflate the balloon by blowing through the hole of the CD, too.
Beware, if your child is not old enough to blow up her own balloons you might find yourself doing more lung capacity exercises than you intended. Brendan is thinking we should modify the design to take an air pump!