I'm planning the next steps in my build whilst my Vermiculite concrete insulating base cures. I've got the space for an external dome diameter of about 1.0m (40"). I'm planning a simple hemisphere with no soldiers/sailors in the dome wall construction. Proportionally, what should the height/width be for the door/vent arch compared to the external dome height/width?
The height of the door lintel should be as close to 63% of the inner dome height as posible, the width of the entry is not as critical but you should aim for at least 50% of the inner width of the cooking floor otherwise it is too narrow to use easily.
If your external dome is 40" allowing 4" walls and 2" insulation leaves a cooking floor of about 28"; your dome will be half that so 14" therefore the door lintel should be around 9" above the cooking floor and 14" wide at floor level.
Thanks for the post oblertone. That's very helpful for my next steps.
I'm looking at the idea of casting the dome with home brew (and insulating with ceramic blanket). Would it work to have the door/vent arch made of clay brick as I think it could look good or are there practical reasons for not doing this as home brew would sit next to clay bricks?
Also, is there any science involved with the chimney height and cross section area to get it to work well?
Homebrew works well with clay bricks and for your arch entry I'd suggest two full building bricks on end and a little home-brew would be fine; only because I used just that on my build. Further I bridged the gap with a piece of angle iron giving me a nice rectangular entry.
There is some science involved re flue diameter but for your size of oven either 5" or 6" internal diameter will be fine. Twinwall sections come up on eBay regularly and most have a register plate that can be bolted or cemented to the arch entry. As to height, a 1m section with a cap will work unless you need more height.
Thanks again for your advice oblertone. My design work is progressing, whilst I wait for my insulating Vcrete base to cure. I'm still on the crux of the decision as to whether to use my clay brick solids for the dome/cooking layer or to go for a cast dome and brick cooking layer.
Advice is available from many sources as you wil know. The 'Traditional Oven' website extols the virtues of red clay bricks and says that cast domes are very susceptible to cracking. Any further thoughts?
Just on this website, which is great, it would be a good feature to be able to go to a 'my posts' feature. Can this suggestion be made to the folks that run the site?