help for rocket mass heater-work in progress

Hi Guys,
we are building our first rocket mass heater, and we need an help for one technical information please.

we would like to know if is better to build an air chamber under the barrel , all around the chimney, connected to the manifold or if it's better to fill the base with clay all the way up to the level of the barrel, and connected to the manifold with only one point for air exit.
Hope it would be clear by these photos and that someone of you could help us.
thank you and have a nice day!

Hi Claudio;
First I will say, bigger is better when getting your heat into the horizontal pipes.
.
I think that leaving as much area open over the manifold as possible is the better choice.
I can not tell how big your transition area is going to be from the photos.
It must be large! It should also (if possible) have a clean out access and an ash collection area.  

Now I will tell you how my barrel / manifold area is set up.  
2/3 of the barrel is over and supported by the core. the other third is open to my manifold / ash collection area before the horizontal pipes start.
The feed box side of the barrel will get a sloping collection of fly ash. The rest settles to the bottom of my manifold. Easy to clean.
Here are a few photo,s showing mine.

thomas rubino wrote:Hi Claudio;
First I will say, bigger is better when getting your heat into the horizontal pipes.
.
I think that leaving as much area open over the manifold as possible is the better choice.
I can not tell how big your transition area is going to be from the photos.
It must be large! It should also (if possible) have a clean out access and an ash collection area.  

Hi Thomas,
thank You so much for your reply and for your explanation, I really appreciated it and you were very helpful in carrying out this beautiful project :-).

I will continue to take photos and document the entire construction of the rocket stove.
Thank you and have a good day :-)