63% on arched entrance clarification please

[dee]

Dear all

on an arched doorway to wfo, is the 63% the top of the arch, the bottom of the arch or somewhere in between? I'm guessing the latter but would like to check.

Thank you
D

[oblertone]

Neither, it's the available vertical gap; from the cooking floor to the highest point of the gap into the oven 👍🏾

[dee]

Thanks, I didn't explain myself properly originally and I should have stated from the oven floor, thanks for clarifying. To confirm then, when I build my 16.5 radius dome the top of the entrance arch to the dome will be 10.4 inches. In the attached pic, it's 10.4 inches to figure 3 or 63* at figure 3(crappy mock up of an entrance arch to wfo).

Figure 1 was the bottom of the arch and figure 2 is the somewhere in between.

10.4 inches, not as high as I was hoping for, but I've measured my oven shelves and never struggled cooking anything with much less than this 10.4 inches. Or am I missing something?

Thanks again oblertone

[oblertone]

At 10.4" you'll be just fine; I used angle iron on top of perpendicular bricks to bridge my 'arch' so mine is on 8" and I've never struggled, even with a turkey 👍🏾

[carboniser]

Jul 16, 2021 8:40:37 GMT oblertone said:

At 10.4" you'll be just fine; I used angle iron on top of perpendicular bricks to bridge my 'arch' so mine is on 8" and I've never struggled, even with a turkey 👍🏾

I did the same, angle iron works great and no need to build a brick arch.

[downunderdave]

Nov 22, 2021 20:03:57 GMT carboniser said:

Jul 16, 2021 8:40:37 GMT oblertone said:

At 10.4" you'll be just fine; I used angle iron on top of perpendicular bricks to bridge my 'arch' so mine is on 8" and I've never struggled, even with a turkey 👍🏾

I did the same, angle iron works great and no need to build a brick arch.

Be careful of using angle iron under the arch because builders have reported, and I've seen it myself, of cracks forming in the brick arch. The problem is the much higher conductivity of the steel means it will expand well before the bricks sitting on top of will, thereby placing stress on the arch form. If a straight length of angle iron is used then a slight gap at each end of around 5mm is prudent to allow for this expansion without placing stress on the brick form. Barrel ovens usually require either steel bracing or buttressing as the half barrel arch is not as stable as a dome. There is considerable sideways thrust on the vertical walls that should be considered. Kiln builders often prefer a catenary arch, which is the only self supporting arch, for this reason and can be built without bracing or buttressing.  An oven only goes to around half the temperature to that of a kiln, but the same principle applies. These expansion problems may not become evident for a long time, especially if the oven is only used occasionally.You can improve the performance of the oven by insulating over the vault.