The skin of the Revell 1/72 scale U-Boat is without question way over scale. The pressure hull of the captured U-570 was found to be 0.88", or roughly 7/8" thick amidships, tapering to 0.63" at the ends. The outer hull thickness is not mentioned, at least not that I could find in a hurry, but the skin on most battlships is not more than 1/2" thick, and on destroyers not more than 1/4" thick. If the outer hull was 1/4" thick then the 1/72 scale hull should only be 0.0035" thick, or one tenth of one millimeter, which might be right for a beer can.
http://www.uboatarchive.net/U-570BritishReport.htm
A 1/4" plate reduced to 1/35 scale 0.007" thick, or about 0.18mm. Beer cans should work, but you'll need strong framing, maybe brass scale I-beams. The actual pressure hull frames were 7.75" T-beams, which in 1/35 scale would be 0.22" or 5.6mm. These are available online or can be ordered through hobby shops.
If I were to build something that size and it was meant to be a static display model and not RC, I would be tempted to construct a complete interior, leaving one side open. The main reason I have not purchased either Revell's U-boat or
Gato class fleet boat is that I would not be able to resist the temptation to do that anyway. Online hobby shops have cast resin compartments and crew figures for the Type VII, and taken together they cost a small fortune, not to mention the etched brass fittings available.
Check out this thread for a modeller who is truly dedicated.
http://www.subsim.com/radioroom/showthread.php?t=123846
Oh, and good luck with this and if you decide to go through with it please be sure to keep us informed of every step.
