Choose a diameter that will fit most of the bottles you own. It should be thick enough to maintain strength over the height you choose to build, but thin enough to let heat escape easily. Now, for the calcuations. Calculate a box that will fit these circles, including each thickness, snugly but not too tightly. You don't want to pipe to be able to bow, but you also don't want to strain the pipe walls by squashing them into the box.

PVC Winerack Instructions

List of Wine Racks

Master List of Wine Products