RMH somewhat mobile I hope

Hi all

I'll begin to work with my rocket mass heater to replace my awful useless stove.

That is my 60cm (23") heat riser with inner diameter of 15cm (6").

It's refractory cement on rockwool tube

Please, can somebody advise me is J-tube better than L-tube for feed tube/burn tunnel compination?

It's easier for wood to burn on itself with J-tube but are there any other difference?

Hi Aki,  I think you have the main reason why people use a J tube instead of an L feed. Unless there are space restrictions, cultural preferences, or just want a certain look, I can't think of any other reason why one is better than the other.
Actually, now that I think of when I build an L tube long ago, I do remember liking that it was a bit easier to clean out the ash from the burn tunnel.

That's quite a 'meaty' riser you built for yourself. It will be interesting to see how long the rock wool will last. There is a video by Bigelow Farms (web4deb) where he used rock wool as a heat riser insulation and there were portions of it that were melted.