On Thu, 07 Jul 2011 16:52:24 -0400, Existential Angst wrote:

It works well indoors, but I'm wondering if I can make it *truly*
waterproof for outdoor use, with enough coats of poly, epoxy, or some
clear plastic coating-type finishes I've seen.

How about marine plywood?

--
Intelligence is an experiment that failed - G. B. Shaw