Ready to build... ...but with questions:

[GregYo]

This is my first oven build. I've been reading over FornoBravo plans, and talking with others on other forums. My plan is to use homebrew 3:1:1:1 (or AR fiber variation) to cast over a plastic mold, and use FB methods to build my outdoor oven. The main body of the oven will be casting only, however bricks will be used on arch. I just finished pouring the cement counter tops, and am gathering materials for the oven build.

Oven info:
Internal diameter will be 29"
Ceiling height: 20"
Door height: 13" (Should this be lower, say 11" ?)
Door width: 16"

The Premio 2G 100G oven has a 65% door to oven height ratio, and this oven would be the same.

Regarding the casting, what do you think about setting up the mold so that it has 3 separate dividers?
The advantages would be: Easy to move; oven joints would easily allow oven to expand and contract.
The mold is a Dogloo, but will be cut down by 6 inches to keep the height closer to spherical.
You have any suggestions on types of oven coatings that help keep it dry, besides a patio cover over it?

[david s]

Your mould is considerably higher than a hemisphere. Not sure how thick it is but it may be quite difficult to cut and remove. You will also need to create an oven mouth, maybe use polystyrene or sand. After casting the dome and mould removal you will need to construct another mould in front of the dome so you can create the cast in situ flue gallery incorporating the rebate for the door. If you are unsure about this there are plenty of well documented cast oven builds under "Other Oven Types" On creating a multi sectioned dome, it is quite difficult to do this using a cast in situ method, particularly if you want to create stepped joints. A single one piece cast is far simpler.

[GregYo]

Yes, the plastic mold points upward, but the sides haven't been cut down by 6 inches. I plan on making the cast about 2 inches thick.

This may be way out in left field, but what if I were to use high strength tape to create a seam, dividing the dome into 3 parts - much like the Casa2g Series dome. The tape would stick up 2-inches above the dome from top to bottom, the cast mud mix would push against the tape on both sides. Once dried, each 1/3 piece would come off the mold and be placed onto the oven floor area with refractory cement on the seams.

If it is reasonably possible, then it wouldn't need to be done in situ. The seams would not be stepped, but the hardest part would be aligning the 3 dome pieces. I plan on casting the flue and the rebate for the door in situ, once the dome is in place.

I haven't seen this done, probably because it may be easier to build in situ with sand cast...

[david s]

Try it and document how it goes.

[GregYo]

David, if I make a 3-peice cast using the homebrew recipe, what is the best refractory cement to use on the seams?
Also, is there a way to move this post into "Other Oven Types" section?

[UtahBeehiver]

I moved your thread as requested

[GregYo]

Amazing how slow things go, when you only have weekends to work. The plastic mold was cut down to the dimensions mentioned above. I sanded down the concrete counter tops, and they'll be ready for sealer shortly. I'm trying to find the instructions on drilling breathing holes along side the insulated dome walls through the concrete base. Where can I find this info?
I need to find the center of the oven on the base, then drill the holes, and finally receive all the ingredients for the homebrew.

[david s]

Regarding your previous question about refractory cement, you can just use the homebrew mix as that's what you are intending for the castings.

For the holes to remove moisture from the dome insulation, they should be placed in the middle of the insulation layer. I use 10mm holes. Use about 4 equally spaced around the dome. Glue some small pieces of insect mesh over them to prevent insect entry. If water or moisture gets in to your under floor insulation a couple of holes near the centre of the floor is also advisable, as under floor moisture is the hardest to eliminate.