If you remember, in my last post about our rocket mass heater adventure, we had an encouraging, semi-successful, first firing. But, because we had only a thin layer of cob connecting the burn chamber to the exhaust system, and got it really hot fairly quickly, the cob cracked. We planned to just patch the cracks with more cob, but worried that this might not work, since the cob was so dry. Just to make sure we had it right, we decided to redo the cob around the base of the barrel. How hard could that be, right?
Brandon used a hammer to break apart the mostly dry cob, and put the pieces in a bucket to take outside. We decided to reconstitute the cob, and reapply it.
Turns out, it wasn't that easy! At least not with the method we invented. Brandon used a sledge hammer to break apart the big chunks, while they were in an empty plastic bag. Then he would pour the busted up small pieces into a bucket with some water.
We left the chunks to soak in the water over night. This worked well. The next day we added a little more sand, and now those buckets of reconstituted cob are patiently waiting for me to re-create the burn chamber to exhaust "gasket" again. Yay... sigh...
Our weekend was filled with visits from friends and family, including my parents and nieces, who came for their fist sleep over in our new place. I managed, despite the exceedingly messing project underway in the dinning room, to get my holiday decorations unpacked so my nieces could help decorate the tree. I even wrapped presents, and got all the surfaces dusted and floors clean at the same time. It only lasted for about ten minutes before Brandon started smashing dirt from the rocket mass heater, but I enjoyed every minute of it!
Ho! ho! ho!
On Sunday morning, with friends and family there to help and encourage us, we commenced building the cob bench that will be the thermal mass of the stove. We've been collecting blocks, bricks, rocks, and pieces of old sidewalks to use as filler for our mass. Blocks were stacked two high in all the places they would fit, and the holes in the blocks were filled with rocks and cob (clay, sand, and straw).
The big chunks of old side walk were busted up with the sledge hammer. Someone mentioned that they can see why they always show prisoners busting big rocks into little rocks in the movies - this is a punishing job!
All that heavy stuff had to be carried into the house and fitted around the exhaust pipes, and all the chinks filled in with cob. Our mass is going to be massive!
We had a pretty good method for mixing up the clay, sand, and straw to make the cob. The sand and clay were put in the tarp, and one person stomped it together while the other person pulled the tarp up and flopped the mixture onto itself to get stomped some more, like folding dough and kneading it. Or like stomping grapes to make wine, only not as sexy.
I've read that some people use horse manure in their cob - thankfully we don't have any so I wasn't tempted to try it. Once the river dance music was blasting, the cob production was happening so fast that we used up all the sand Brandon had purchased for the day, and more had to be fetched.
I was frequently distracted by food preparation, but every time I tuned back in to the progress, I was amazed at how much was accomplished in such a short amount of time. And, all that weight didn't collapse the house, so that's good. We placed the heavy cob bench so that it crosses all the beams that support the floor, and when we were repairing the floor from the termite damage, we added extra supports in this area, because we knew the bench would weigh a ton.
There have been lots of things about this job that were strenuous, and I think one of the most back breaking has been putting all the bricks, blocks, stones, and pavement chunks, into the bench. It required a lot of bending and lifting, which ain't easy.
Having the tarp on the floor while we were working helped with the mess. Sort of.
After we finally called it a day, Brandon and I were soaking our weary bones in the hot tub and reminiscing about the days work, when Brandon said I should put it out there in the universe of the internet that building a rocket mass heater is "a shit ton of work". It literally is a ton of work! We knew it was going to be a challenging project, but in his fatigued state, he was adamant that the books and the personal experiences we've read on-line do not really emphasize how much strength it takes to build one. Every shovel full of sand and clay is handled multiple times (especially if you decide to re-do parts, like we did), so it's physically hard to do. Lifting, stacking, bending, getting down on the floor and back up over and over. It's hard. I sort of love that about it, but at Brandon's request, I'm putting it out there. It's a ton of work.
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