Take a look at this:
I've always been impressed by people who could weld soda cans together, and so I gave it a shot today. It's actually easier than I thought. The cans act as great heat sinks, and the bottom of the can is a rolled "edge" (ie it would be MUCH more difficult to cut a can in half, then butt-weld the paper-thin aluminum edges together). Of course, my weld is not really pretty, and I did blow through the material on the other side of the can... This exercise reminded me how much I need to work on holding the torch at 90* to the surface when going around a cylinder.