I'm running out of stuff relevant to my current rocket stove projects in my current collection of random junk. In particular, I don't have much sheet metal or ductwork of suitable diameter. So I'm wondering where I'm likely to find something. I've got an old water heater core, and I suspect that there are plumbers out there ready to give water heaters away. Hmmm....I had only been thinking about the cores, but actually the sheath is sheet metal too, isn't it? Could do some interesting things with light sheet metal and the concrete reinforcing mesh I have on hand. I could probably make a decent barrel stand, something that would be adequately air tight — a low bar, in my experience to date — and less of an investment of effort than a half-barrel like the one I made. Tin snips and pop rivets rather than a sawsall.
But anyway, I'm just fishing here.