To get a feel for the materials and kinds of difficulties that might crop up when presenting a complex problem to new tinkerers, I like to fool around with the materials my self a bit. Here’s a working powerplant for a rubber-band powered boat made entirely from recycled materials (except for a bit of waterproof tape).

Ingredients: juice bottle, soda can, rubberband, bit-o-wire, bit-o-tape.

A paddlewheel turns out to be a little more complicated than expected. Ingredients: soda can, bit-o-wire, bit-o-tape.