Test Firing the Bunk House Rocket: Uncle Mud at the Rocket Mass Heater Jamboree 2021

We're coming down to the last days of the 2021 Rocket Mass Heater Jamboree at Wheaton Labs. This Rocket Mass Heater is heading into a cob bench inside an underground cottage (WOFATI) to hopefully take the chill off things, but first we are in the shop parking lot testing the darn thing to make sure it even works. Rocket Mass Heaters are experimental. We know the principles work, but when we custom build one to fit a particular space we are making an educated guess. Which means you don't fire it up for the first time inside where the results might be a lung full of backdraft or a building on fire. This one works gangbusters with a 6" chimney, but not with a 4" chimney as was originally intended. This was good to know before we had it buried in a cob bench 3 miles from our shop and tools. Thank you for supporting us at   / unclemud