Hi Ron; Yes , these stoves are fun! I have been obsessed since i first heard about them. I tell anybody i meet all about them and how cool they are ! I'm sure most of them think i'm some kind of crackpot. My cast core is an 8" and it is apx 4" thick on all sides built mainly out of fireclay & perlite with some refractory added (yes its very costly) I built it with a plywood outer form and let it air dry for a few days and then wheeled it into the backyard and fired it off. It took a few firings before it started to hold heat , my chimney for that was simply a piece of reg stove pipe set on top. After the core was fired (still in its plywood box) it was moved into place in the green house and stripped the outer form once it was in place. My riser is also a casting done using fireclay & perlite ,with a 16 gal grease barrel for an outer form and a piece of 8"
cardboard concrete form (sonitube) as the inner form. This worked perfect! I built it in place on top of the cast core, the cardboard tube burned out with the first fire leaving a smooth bore insulated heat riser , that has lasted all season with no issues at all ! I wish I could say the same about the core. I have had problems with wear on my
feed tube side that i patched several times this winter including using
water glass to harden the surface.Not sure why i'm having problems with the core casting most likely i didn't mix as well as i thought. I will be replacing the core this summer and I will use all refractory (despite the cost)with some perlite added for insinuative value. I hope to be able to lift off the riser and set it back when the new core is in place but not sure if it will handle moving or not. Have fun Tom