Pompeii oven opening

[woodsman]

Hello all from Queensland Australia. I'm trying to build a 900mm dome oven using the Forno Bravo pompeii plans, have completed the block stand and have reached the tough bit

I'm trying to decide on a design for the oven arch and flue support. Do you think it would be structurally sound to build a half-brick arch as an opening to the dome separated by board insulation from an arched masonry box to support the flue and transition? The dome arches on this site don't seem to be bonded into the dome except by mortar.

I'm thinking to separate the two arches because of concern that having a large volume of masonry directly mortared to the dome and not insulated will lead to significant heat loss. It seems obvious but I can't find any reference to this issue on the site.

There has been some discussion on cost and availability of 'fireclay'. Here, our local Bunnings sells 20kg bags of a product labelled as fireclay for less than $10. It states on the packaging that it is used by bricklayers for general mortar purposes where the sand is deficient in clay. Could this be the fireclay referred to in the plans?

Any suggestions on these points would be really appreciated

Stuart

[toyota08]

Hi Stuart my bunnings didnt have the fire clay so as per aussie Russell jeavons book im using orange brickies sand has the clay in it,it comes in white as well.Russell uses his ovens commercialy 2 days a week for the
last few years no probs mate.look up his ovens in the reseraunt threads
by nissanneil.
Cheers Peter

[toddj]

Woodsman, I thought the same thing and am isolating my chimney structure from my dome by about 1cm gap. I also came up with a stronger arch design for my free standing chimney.

http://www.fornobravo.com/forum/f28/...arch-4882.html (A stronger arch)


...

[christo]

I did not isolate my entry from the oven and don't believe I'm seeing an appreciable degredation in performance.

My entry arch is one piece that also supports the oven opening. I see no reason why it could not have been made in two pieces.

If it looks like a lot of work and you don't plan to run the oven for a few days at a time, I'd skip it. After a pizza night, my oven is still too hot the next morning to bake bread.

Christo

[karl]

I guess the opening is a weak point in the oven w.r.t. the expansion forces during heat up. They will tend to "rip it appart" (widen the opening). It is sensibel to try to hold these forces by making a solid arch and opening (extending radially) so that the opening does not give in to these forces and reveal it with a crack.

karl