barrel seal?

what do people use to seal the barrel to the cob? with the contracting and expanding i would think a flexible seal would be needed. wouldnt the barrel crack the cob upon heating up?

thanks

lol taboo question?

Hi Ron; No, not tabu... I had answered that very question in the previous post (Transition area) Thought that you saw it. So my answer is fire clay & sand to seal the riser and the same with the big barrel, only with the big barrel you also use several inches of cob after you seal with the fire clay and sand. Also you are going to have some cracking on your build to start with, the beauty of cob is a little water and some more cob and its good as new.

thank you for the response Thomas. thats a hard concept for me to grasp. do you have to reseal the cob around the barrel much? could i use a layer of rock wool or something, at the bottom, just to ease my mind . or would that do more harm than good?

thanks again

Ron; I ran my rmh in the greenhouse hard , all last winter and although i had other problems with a cast core I never needed to reseal the barrel to the core. For me the cob ends up being 3-4 " thick around the bottom of the barrel and it never even cracked in that area. I don't know about using the rock wool around the bottom , i suspect that its not needed.

Ronald Bush : I would rather start out my day pissing off a Nun, that be guilty of putting words in Ernie or Erika Erica Wisner's mouth but - when they do
a full workshop weekend, they immediately and continuously keep the Rocket Mass Heater, RMH, and Barrel fired and Hot (Expanded )!

As I understand their thinking, the barrel heated and expanded, will make a better seal without cracking than making a good seal while dry and cool - then
promoting over-expansion while heating !

Remember that you are using the least expansive local clay or Bags of Lincoln 60 'Fire' clay from your favorite Big box store mixed with builds grade sand,
which further limits expansion and contraction ! This has worked very successfully for me ! Hope this is timely and helps,Good luck !

Think like Fire ! Flow like a Gas ! Don't be the Marshmallow 1 As always your questions and comments are Welcome and solicited ! Big AL !