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Summary
part 2 of a 2 part podcast
Paul and others continue to discuss improvements to the
rocket mass heater in the library, and rocket
heaters in general.
Paul comments that a pebble style mass as previously in the library can be moved and rebuilt someplace else, which you can't do with
cob. However there's a trade-off that initially the rocket heats the mass more slowly.
Peter is invited to comment on the rebuild. He re-iterates the point that bypasses and such are prone to human error.
He has the following comments:
* 4" flue is only a quarter the area of 8", so it's too small. 6" could even give problems.
* A given size batch box is about twice the power of a J tube, but you do need a bigger/better heat extraction to use the heat efficiently. Peter has a build with a tall stratification chamber, about 6ft high and maybe 2ft x 2ft
footprint.
* He suggests making the connection from the rocket heater to the stratification chamber larger. There's no need for restriction at that point and a wider connection will speed up heat transfer to the chamber. He also points out that without a single flue (as with a mass) more fly
ash might gather in the stratification chamber.
Paul feels not
enough has yet been done to improve efficiency when the stove is not burning which is what they are experimenting with on this build. For example, the smaller exhaust
should conduct less cold air in from the outside when not burning, and kissing the barrel mitigates the possible draw issues with the smaller exhaust.
The last part of the podcast has some questions and answers from the live session.
Paul finishes up by stating his position that anyone starting out in rocket heaters should start with a J tube as it's a simpler build. Batch boxes are harder to build if you don't already have the skills, so it's easier to get it wrong. Peter agrees that the batch box is more complex to build but the payoff is bigger as well. Paul reasons that as the batch box burns more
wood, faster it is better suited to places like a
workshop or cabin where you want heat fast.
Relevant Threads
Rocket Mass Heater forum
pebble style rocket mass heater in the library
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This podcast was made possible thanks to:
Dr. Hugh Gill Kultur
Kyle Neath
Bill Crim
anonymous
Chris Sugg
Kerry JustTooLazy
Jocelyn Campbell
Bill Erickson
Sasquatch
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Julia Winter, world's slowest mosaic artist
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Eric Tolbert
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Opalyn
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Todd Gerardot
Katie Young
Ivar Vasara
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Weston prestage
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Song Zheng
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