I made a cardboard box upright bass using scrap oak flooring as the neck, and i made a pickup by breaking away the plastic casing of a Radio Shack Science Project Buzzer, and strings are weed whacker twine and the tuners are faucet-spiggots.
the cardboard bass plays great and sounds wonderfuL.

heres a vid link for proof...
www.youtube.com/watch?v=c6cTbaBApM4

the project took a little more than an hour and i'm still tweaking it.