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Summary
part 2 of a 2 part podcast
Paul and Uncle Mud continue to discuss the red cabin RMH, now they are looking into optimizing it further. Paul feels the J tube is ideal as it has plenty of scope for optimization.
Paul has in mind reducing the heat absorption some, in order to make cold starting easier and increase the draw. To make up for this they will add a
cob hat, as was done in the love shack. The heater will run faster and harder but get the same heating inside the cabin.
Paul credits Uncle Mud with the idea of the cob hat, and Mud recalls the early efforts using stones on the top of the barrel which weren't effective. Mud also thinks the top of the barrel could be replaced with cob, but Paul suspects that it might be prone to leak.
Paul also has in mind that the gap between the barrel and the cob hat can be used to bake cookies or other foods.
They consider the shape of the cob hat, and Mud talks about how the shape of the hat could be used to direct radiant heat where it's wanted: an inverted cone shape could send heat downwards which would be good.
Mud also wonders if the stainless barrel is already passing more heat through to the mass, since stainless doesn't conduct heat the same as mild steel.
They agree that adding a sign with cold starting instructions would help. They also talk about moving the cleaning/priming port nearer to the vertical exhaust. Uncle Mud feels that improving the priming port might avoid the need to reduce the mass efficiency.
Paul is thinking about putting cob between the barrel and the exhaust, which could transfer some heat to the exhaust and improve draw and cold starting, and also installing a layer of cob between the barrel and the wooden wall so as not to need the currently-fitted metal heat shield which protects the wall from getting too hot. Mud comments that he's seen cases where an RMH is run for extended periods, and the outside of the cob eventually gets hot
enough to be a fire risk.
Relevant Threads
Rocket Mass Heater forum
Wheaton Labs forum
The Red Cabin
Minnie Mouse Fitted with a Cob Hat
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