Heat retention versus oven size

[paulkjrobbins]

Thanks for the advice Russell. I will lower mine in. I know there will still be a little variance since the fulcrum from the caster wheel pivot is not centered over the center of the dome arch but I think I am just getting picky if I get too crazy with things like that. Is the 65% calculation preferred over the recommendation in the general forno bravo plans (attached- pg.13)?

[UtahBeehiver]

It 63-65% of dome height is a rule of thumb and subject to much discussion. An old white paper called Bread Ovens of Quebec showed that the majority of the early pioneer ovens had opening is the 63% range. The FB is for the 42" is 59.5 range. Will it make a difference, probably not..More recently builders have been using the 63-65% ratio, builders choice. On the IT, as long as you are aware of how the vertical and horizontal offsets effect the dome diameter and make adjustment you are fine. The offset does effect how the dome and arch tie together if you do a tapered inner arch (recommended).

[paulkjrobbins]

The weather has been wet here so I am still waiting to start mortaring in my first course. One more question I am wondering about is in relation to the chimney pipe. I am doing an 8" double-walled SS pipe. My oven is being built just outside of a pavilion so the chimney will extend 2' past the ridge of the pavilion giving it plenty of draw, it should be pretty stable as it will have a support rod from the pavilion roof. I have read a lot of posts that comment on how attaching the anchor plate to the firebrick with expansion bolts will crack over time. What have people done instead of anchor bolts? Is an anchor plate needed necessarily? Can I just flange the bottom section of the chimney pipe and encase it in homebrew or vermicrete? Perhaps mortar another layer of firebrick on top to encase the seam? I am doing a gabled enclosure with hardiboard so it won't be visible and doesn't need to be super pretty. Any thoughts would be appreciated.

[MarkJerling]

My oven's flue pipe is simply bricked and mortared in. It's been 100% stable.

[david s]

The weather has been wet here so I am still waiting to start mortaring in my first course. One more question I am wondering about is in relation to the chimney pipe. I am doing an 8" double-walled SS pipe. My oven is being built just outside of a pavilion so the chimney will extend 2' past the ridge of the pavilion giving it plenty of draw, it should be pretty stable as it will have a support rod from the pavilion roof. I have read a lot of posts that comment on how attaching the anchor plate to the firebrick with expansion bolts will crack over time. What have people done instead of anchor bolts? Is an anchor plate needed necessarily? Can I just flange the bottom section of the chimney pipe and encase it in homebrew or vermicrete? Perhaps mortar another layer of firebrick on top to encase the seam? I am doing a gabled enclosure with hardiboard so it won't be visible and doesn't need to be super pretty. Any thoughts would be appreciated.

This is my solution, it works pretty well. If mortar is sitting around the flue pipe the hot expanding pie can crack it. I use vermicrete to support the base of the pipe which has some give to it. If you are using a double flue this shouldn't be a problem as the outer flue will be considerably cooler.

[paulkjrobbins]

Thanks David, that picture explains it reall well.

[mongota]

TI have read a lot of posts that comment on how attaching the anchor plate to the firebrick with expansion bolts will crack over time.

I used four anchor bolts to secure my chimney plate. No cracks in the bricks. The drilled holes are larger than the actual bolt diameter, so very little of the anchor contacts the brick. I have a ~2-1/2" thick cast concrete cap that covers the anchor plate. It's going no where. Zero movement/sway in the chimney.

[paulkjrobbins]

Mongota, that is some awesome stone and concrete work on the outside. Did you do that yourself?
Did you have to use any special concrete mix when capping it? By that I mean, was heat an issue, or was it negligible since it was on the outside of the flue?

[mongota]

Mongota, that is some awesome stone and concrete work on the outside. Did you do that yourself?
Did you have to use any special concrete mix when capping it? By that I mean, was heat an issue, or was it negligible since it was on the outside of the flue?

Thanks.

Yes, I built it myself.

The concrete corner pillars, slabs, arches entry shelf, and chimney cap are all plain ole Quikrete with carbon black/charcoal colorant added. Heat is not an issue with any of those castings. I had thought I might need a heat shield of some sort for the underside of the arch casting that surrounds the opening on the front landing, as I though it might see too much heat when starting fires right at the opening. It has not been a problem.