Oven/Vent opening

[nodison]

Hey All,
I am about to start construction of my oven, I will be building the 36" high vault model, space prevents any bigger. I am going to do the vent/oven opening in an arched brick. In the instructions it calls for a 19" opening width and a 12" opening height. My question, is the 12" opening height measured at the highest point of the arch or is it measured from either end of the opening, up 12", and the arch above that... I hope this question makes some sense...
Thanks in advance....

[morrishuckeba]

Re: Oven/Vent opening

12" opening height measured at the highest point of the arch

[nodison]

Re: Oven/Vent opening

Thanks, that clears it up nicely

[luca]

Re: Oven/Vent opening

Speaking of vents, has anyone made a barrel vault without a vent? I made a cob oven once without a vent and it worked fine, but was hard to start. I'm wondering if the vent helps with fire starts as well as the smoke-in-the-face issue? I'm planning to make a brick barrel vault and the vent looks like a lot of headache. I'd appreciate some input!

[Tscarborough]

Re: Oven/Vent opening

I don't think you need it, but I do think it helps with both smoke in the face and more importantly, with the ability of the oven to light easily and burn hot. Look at the way I did mine. It took me a while to figure out how I was going to do it, but the actual construction was simple.

[luca]

Re: Oven/Vent opening

Great pics!!! Your oven is very similar to what I'm planning to build, and I've got tons of questions. The first is, where are You??? Your firebricks (giant sized?) and vault bricks (long and thinner looking) look very different than anything I can get here in Vermont. Also, your oven looks smaller than most--which is what I'm wanting to build--what are the internal and base dimensions? Also, the debate continues over vault vs. dome shapes; have you found "cold spots" in your barrel oven as many allege?? Finally, you are right about how you built your chimney; it looks doable even to a newbie mason like me! Tx!

[Tscarborough]

Re: Oven/Vent opening

The floor bricks are standard 4-1/2"wx2-1/4"hx9"l. The ones on the vault are called "splits" and are 4-1/2"wx1-5/8"hx9"l that I ripped lengthwise to minimize face joints. The ones on the inner arch are whole splits. The floor dimensions are 22"wx36"w with a vault height of 24", if I remember correctly.

I can cook 3-9" or 11" pies at a time. When cooking, I bank the fire all along the left side, and there are no hot or cold spots that I can tell. The vault will generally be 100-150' hotter than the floor until I close the door for a couple of hours, then it evens out within a few degrees. The only change I would make is to offset the door more so that on the right the inner arch would be flush with the vault wall.

[GianniFocaccia]

Re: Oven/Vent opening

Tom,
My brother is weighing heavily the construction of a barrel vault oven patterned after yours. I mentioned to him your idea of an offset door flush with the vault wall. He replied that he was thinking of making a vault wider than deep, maybe 36"w x 30"l. Do you think these dimensions are practical? Do you think a slightly offset entryway help?

John

[Tscarborough]

Re: Oven/Vent opening

DamnifIknow. I don't see why it wouldn't, but for those dimensions why not go FB style? The main reason I did barrel over onion is that I wanted to build a vault using the Timbrel method. Hell, that is the only reason I decided to build an oven is because I wanted to build a Timbrel arch! It just got sideways from there.

[GianniFocaccia]

Re: Oven/Vent opening

Wow Tom!

I noticed on your (very handsome) build you had several layers of vault bricks but was not aware that it was a specific arch methodology or the name of it. A quick research at this site

Make: Online : Lost Knowledge: Timbrel vaulting

came up with this:

"If just one layer of thin tiles was used, the structure would collapse, but adding two or three layers makes the resulting laminated shell almost as strong as reinforced concrete."

I wonder if anyone would try this with splits a Pompeii...

[Tscarborough]

Re: Oven/Vent opening

Well, I have considered something similar, but you would need 3/4" tiles, then add mass once it is complete. The advantage would be in shipping and rapid assembly (It took less than 4 hours to build my vault for example).

[GianniFocaccia]

Re: Oven/Vent opening

I would imagine 3/4" thick (running bond) tiles the length of the vault x three layers and 2-3" of refractory mortar added would work. Think of how low and shallow an arch could be made! I wonder how the mortar between the tile layers would tolerate the thermal cycling?

[luca]

Re: Oven/Vent opening

I have some advice on building the vault wider than deeper John;DON'T! I first built my clay/ cob oven that way and found that I could not get it hot enough, AND the fire wouldn't start easily! Fortunately, since it's only clay, I filled in the opening and made a new one on the end, and the difference was dramatic! So, I guess the lesson is the vault has to allow for a circular air flow from the base of the opening through the fire mass and then back out the top if it's to build heat properly. (FYI, somewhere in this forum are pics of by build, along with a shot of the "old" opening filled in).

[GianniFocaccia]

Re: Oven/Vent opening

Luca,
Thank you for your valuable input. I always wondered why vault builders didn't design a more 'user-friendly' footprint with cooking space on either side of a central fire. I guess this is precisely why.
John