rocket mass heater shippable core - wood box style

Ok i am a total newb to this but i had a thought i will just toss out...

I dont know the price of it or if it would work but the metal sheeting that people put around woodstoves when they are closeish to walls etc or on the floor under it.
Could you have five squares of that, one for each side and bottom... or just for the most burn prone sides?

I was thinkin if that would work it might cut some of the other costs for more the brick etc.

Good luck!

Bump to show what the core looked like

Why not paper mache forms that you could burn out?

Could be a good idea if you can keep the paper mache core form rigid long enough for the castable to stiffen up.

Varnish the outside of the paper mache? I'm just guessing here folks....

It has been stated by experienced people that a one-piece core casting is more prone to cracking (as in always does it), and it's better to cast a core in sections. So if you want to use paper mache for your personal build, try it, but it's probably not reasonable for commercial production.