Oven floor insulator materials and process…

[UtahBeehiver]

Go to the section where you want the thread (suggest pompeii construction) the hit "new topic"

[mnagy]

How do I go about making a build thread? I made a video of me building my stand. Was gonna make a separate video for each step and put it in a thread on this forum for feedback. Thanks!

[JRPizza]

I debated whether to do a fourth course of block for the stand, but opted to go lower. I’m ok to bend over a bit if it keeps things at a standard-looking height. I’m at around 29/30 for the stand. Add 4” of vermicrete and 2” bricks, gets me to about 36” to the oven floor (which I’m happy with.

i can definitely make the chimney opening more like diagram B. I can come out a bit more if I have to, but I’m hoping to get away with just 4” beyond the dome line for the entry.

Going from rectangular to round is a piece of cake - I did it with bricks so casting or welding should be trivial. Also if you decide you want more height to the oven floor you can always (at this point) pour a thinner overhanging hearth over the top of the existing one giving a bigger footprint and adding some height. Or if you decide you are totally screwed on room for the entry you could add a "shelf"/extension in the front like some folks have done or even drop to a 36" ID to gain 2 inches. Due to the weight of these ovens you kind of need to know what your final configuration will look like before you start or you can easily end up with too big or small of a hearth and/or sub-optimal placement. On my cad design I indexed all my plan form dimensions from the oven center point which made it easy to locate everything on the hearth.

[david s]

Apart from the brick's form make sure they are dense firebrick not insulating firebrick. If they are super duty bricks they'll chew up diamond blades like crazy. Medium duty dense bricks are probably your best choice.

[UtahBeehiver]

I suggest you read the "brick primer" in the FB plans and make your decision.

[mnagy]

Wow. Good point. A dozen blades would be like $400+. Would you rather have heavy dusty bricks that stay warm longer? Or lighter bricks that heat up faster?

[UtahBeehiver]

I used tapered bricks that were wedged in the opposite direction and they worked fine. These are bricks are wedged front to back vs side to side. So it will be more difficult to control the angle determined by the IT. The internal face of the brick MUST be perpendicular to the center point on the floor. But is possible to work around as long as you know the dome parameters. These are possibly superduty bricks which means extremely hard and will take a tow on diamond wet blades. I went through a dozen on my build so it this it the case you need to weigh blade cost versa brick cost.

[mnagy]

Another question: I found someone selling fire bricks cheap, but they are a slight wedge shape (see pic).

if I got these, I was thinking I could cut them in half and just use them for the dome (making sure not to mix the big/small wedges within a course.

would that be helpful? Or would it just complicate things and I should just get flat bricks.

[mnagy]

I debated whether to do a fourth course of block for the stand, but opted to go lower. I’m ok to bend over a bit if it keeps things at a standard-looking height. I’m at around 29/30 for the stand. Add 4” of vermicrete and 2” bricks, gets me to about 36” to the oven floor (which I’m happy with.

i can definitely make the chimney opening more like diagram B. I can come out a bit more if I have to, but I’m hoping to get away with just 4” beyond the dome line for the entry.

[david s]

A square brick opening will result in a deep entry. The same cross sectional area can be achieved by a narrow rectangle, leading to a far shallower gallery. If the area at the base of the gallery is larger than at its top where it joins the flue pipe, a smoother smoke flow and extraction results.

This pic might explain better what I was trying to say. Design B will have a much shallower gallery as well as a better performing flue than design A.
+1 on Gulfs obsevation. The foundation slab may also be interfering with you being able to get close enough to the oven.
The Valiorani oven pic I posted in #26 I built on a circular supporting slab, so it is possible to do the same on a square footprint with considered design input.

[Gulf]

I was concerned from the beginning that you were going to have some issues with having enough room for even a shallow entry. I figured then that with some research that you would find that out. But, since the cat is out of the bag, here is one more thing to consider. That would be an ergonomic working height for your finished oven floor. Most recommended is the bend of the elbow while working the oven. I actually like it a little higher. I recommend the xiphoid process. My old back doesn't like working in a bent position. For me, the bend of the elbow would be 42". I'm guessing again from the pics that you are going to end up with about 38"? I'm just throwing this in to give you some things to think about when designing in elevating insulation from the hearth floor and possibly cantilevering fore or aft for your entry if needed.

[david s]

A square brick opening will result in a deep entry. The same cross sectional area can be achieved by a narrow rectangle, leading to a far shallower gallery. If the area at the base of the gallery is larger than at its top where it joins the flue pipe, a smoother smoke flow and extraction results.

[mnagy]

Lots to think about there, thanks! I don’t have anything figured out completely, but I needed to make a square stand, so I’m gonna have a much shorter entryway. I really only have about 6” beyond the outer dome footprint. My plan was a metal chimney attached to a custom fitting (which goes from a square brick opening to a round metal chimney).

[david s]

Brick oven builds generally also have a flue gallery built with bricks, as in the Pompeii brick build plan. Unfortunately this leads to a deep entry which has the disadvantage of being heavy and the flue gallery therefore acting as a heat sink, drawing heat out of the dome and therefore requiring higher fuel consumption. Additionally brick units do not lend themselves to creating curves let alone compound curves. I think the tradition of brick building to use a brick flue gallery comes from having more bricks available than is required for the dome as well as wet brick saw on site, it seems logical to continue the build with brick.
A flue gallery built in steel, or cast refractory can be thinner, lighter and shallower than one made in brick. This means better efficiency and far easier working of the oven, allowing better access and shorter handled tools.
If fabricating in sheet steel it should be stainless and at least 0.9mm thick. If cast it can be done with either homebrew castable or proprietary castable refractory and probably no thinner than 25mm,

The attached link and pic provide some ideas.

https://community.fornobravo.com/for...723#post435723

[JRPizza]

Entry tunnel length can indeed vary quite a bit, and the large variations are obtained by type of construction (forgive me if you already have this sorted out). A cast or even welded vent can facilitate a very short entry, whereas bricks are typically 1.5 bricks (~13") long with some variation on how they tie into the dome etc. Have you a method/length in mind?