Anyone ever seen one of these or played with one before? Its been floating around for quite some time now. I found it a few years ago and just stumbled upon it a few days ago. I'd imagine if you took one of these in a public area you'd probably get some funny looks and perhaps a bit of trouble...
The physics behind how it works is awesome.
The PDF gives cross sections and rough instructions on how to build one. I'd love to hear one sometime, but it looks like quite the project to build one.
Download the pdf here