Here is some pics of my home made owb that I built. This is the 4th owb I've built. its basically a 1/2"wall x 42" diameter, 6' long pipe for the burn chamber. that is put inside a 52"dia x 3/4"wall x 7' long pipe. it holds 310 gallons of water. all in all it cost about 3700 in parts to build it and took about 220hrs. the handle above the door is a smoke bypass, so I don't get a face full of smoke when loading it. the estimated weight is about 5200lbs. the spray foam cost about 540. but it will pay for itself eventually, just like the boiler itself. I also built it with an ash auger, on the bottom of the burn chamber.