Glenn Herbert wrote:Not addressing other factors, I don't see any reason to exit the tub at the bottom. Just turn the duct and head straight back up - that gives more heat exchange surface and makes construction considerably easier.
Glenn Herbert wrote:For the fuel feed, the drawback to a batch box is that it burns intensely hot and can't easily be stopped if your water overheats. Rather than a tube above the J feed, I would use a cage of vertical strips of sheetmetal, maybe V-crimped for rigidity, with gaps between, held together by hoops on the outside. The idea is to present a smooth vertical interior surface with nothing that a knot could hang up on, while leaving lots of open space so the feed can't form a hot chimney. With the whole thing being in the open air on sand/rock near water, I don't think safety is too big of a problem, as long as the whole thing is properly stabilized.