Wanted to brag about my new portable Rocket. It's nothing earth-shattering but being portable is very helpful for demonstration purposes. Plus the stovepipe flange on the side of the drum makes it really easy to plug into a bench or 50 gallon drum bell or chimney. The core is a 6" from DragonHeaters http://www.dragonheaters.com/?a_aid=industrialrustic (yes I am promoting them). It's in a TractorSupply Job Box full of vermiculite.
Cob is sand, clay and sometimes straw. This tiny ad is made of cob:
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