Fall cleanout Rocket Mass Heater & how to reconstitute cob
You'll see in my "Pandemic Project pages, Phase 7 was a Rocket Mass Heater.
Well, it's been humming along happily during the winter for the last four years burning less than half a cord of wood with fires that last 1-3 hours depending on how cold the night will be.
A RMH should have a cleanout at every turn & be vacuumed out annually. When I built mine, I initially didn't know there was such a thing as a "cap" for open ends of ducts. So for the first cleanout next to the manifold, I fashioned a can with a woodstove rope seal & then I cobbed that sucker in.
It's worked fine, but every fall I need to remove & reconstitute my cob, do my cleanout, then re-cob it back in.
Here's pics of that process I finished this morning. It took less than an hour to break up the cob two days ago & maybe two hours this morning to recap all three of my cleanouts, two with real ducts caps (one with foil tape the other cob since I didn't leave enough room for tape) & the last, the one below next to the manifold.
Btw, I put a flagstone on this end of my adobe floor under this cob to handle this annual re-do work.
Well, it's been humming along happily during the winter for the last four years burning less than half a cord of wood with fires that last 1-3 hours depending on how cold the night will be.
A RMH should have a cleanout at every turn & be vacuumed out annually. When I built mine, I initially didn't know there was such a thing as a "cap" for open ends of ducts. So for the first cleanout next to the manifold, I fashioned a can with a woodstove rope seal & then I cobbed that sucker in.
It's worked fine, but every fall I need to remove & reconstitute my cob, do my cleanout, then re-cob it back in.
Here's pics of that process I finished this morning. It took less than an hour to break up the cob two days ago & maybe two hours this morning to recap all three of my cleanouts, two with real ducts caps (one with foil tape the other cob since I didn't leave enough room for tape) & the last, the one below next to the manifold.
Btw, I put a flagstone on this end of my adobe floor under this cob to handle this annual re-do work.
Above: using a stone chisel to break up cob
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The home-made duct cap is revealed
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Above: Cap removed. Note fiberglass rope to improve the seal.
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Looking into the manifold
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This is everything vacuumed from all my ductwork from one year of burns, not even a pint of material
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Above: all cob from two covers.
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Cob broken up with a hammer; note board under it so you don't crack your mortar trough
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I added a bit too much water so it had to sit in the sun for two days
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Above: cob pulled into piles with a hoe (w/broken handle)
Spray wall about 30 minutes before cobbing then paint with clay slurry |
First bit of cob reapplied. Note: I covered my can with a piece of landscape cloth to minimize rusting
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My trusty Japanese trowel for making it pretty. Of course it works best with sifted sand in plasters but it works okay on regular cob.
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Above: All done keeping the top as flat as possible for my tea bowl.
Tools: 1. Long skinny trowel good for compressing cob along seam at the top smoothing it into existing bench witha lot of pressure it can handle. 2. Middle "trowel" replaces my favorite small trowel that was accidentally cobbed into a wall long ago (I still miss it!). This one is a vintage "fish spoon" bent to make working angle 3. Tiny Japanese trowel ordered online @ JapaneseTrowels.com ...So sweet that little trowel I keep it in a small box with my masonry tools.
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Above: got wood delivered plus about a third leftover from last winter (so I used less than half a cord!)
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