Make a wood fired hot tub

Got a bunch of copper pipe, a portable woodstove, and a giant metal barrel thing.  Hey you too can build this funny gizmo for a hot tub.  I like the copper idea but I can imagine the pipe getting pretty grimy after a while.   The author puts the cost at $650 in materials.

http://www.instructables.com/id/Wood-Fired-Hot-Tub/