Seeking input for RMH for sauna

So, I've been reading up on threads on RMH, and focusing on anything sauna related. A few question have come up for me as a I progress in the design process. I'm designing a 2 room sauna. (Roughly two 7'x7' rooms). Wood storage and feed on one side of a cob dividing wall and riser, barrel and mass on stove room. One post mentioned low mass 8" system with extra space between top of fire brick riser and top of barrel. Not sure what's the optimum (and simple without reinventing anything) design for this application. Something that kicks out a lot of heat quickly to get sauna to temp nice and fast.

Any input on these questions is welcome

1. 6" or 8" ( I wil keep consistent diameter throughout system)?
2. Ideal spacing above riser and barrel for optimum quick heat through barrel?
3. Does the idea of low mass make sense to kick more heat into room in a hurry?
4. Given sufficient chimney rise, does the length of interior pipe run effect burn and immediate heat dispersal.
5. Any thing else I may be missing.

I'm not looking to tweak or tinker, just succeed at getting a stove room up to 200F as effieciently as possible. Advice greatfully accepted. If all goes well, I'll document the build and share it for the benefit of all.

The plan so far is a slip chip and round wood post building with extra stout wood joists under heater over tile floor. Sawdust and lime cieling insulation and am considering Eco foil bubble Wrap for VB in stove room. Does this sound like a good idea or not? Still working out engineering and other details, but the stove is the most essential element IMO.

Thanks for all those who keep learning and sharing!

Hi Ian,

I've been in a BBR sauna of around 2m x 1.3m and the heater was only 4.5 inch.
Fed from outside the sauna room to reduce cold air being drawn in.
The bell is an oil drum with a manifold on top and heat rocks.
Sauna has no trouble reaching 100c in a short time.
I hope this is some help.
I would have thought that cob would slow the room heating up as it is thermal mass.
I believe that you want the room to be as insulating as possible and very little mass in the bell for fast room temperature increase. Otherwise you may have to plan your sauna hours in advance.
Also anything dense in the sauna will be extremely hot to the touch compared to something like cedar.

Behen,

Thanks for sharing, it helps generate some ideas. Is the manifold a custom designed item, or is it repurposed? I too like the idea of outdoor feeding for stove and am planning on insulating well. Luckily there is plenty of cedar around here. I think I'm leaning towards a similar rock on bell design, perhaps with some mass on horizontal exhaust.

Hi Ian,

Yes I believe he cut the top off of the drum and made a custom manifold in the shape of a +

Looking forward to seeing progress!