Vent / landing

[Cameroonian Kid]

So I should've posted this a day ago, but I've already started my build..

I'm building a high dome 105 cm Pompeii, with an opening that is 12 inches high, by 20 wide.

my question is in relation to the vent landing mainly because I am confused as to where it starts and where it finishes...

my arch starts where the internal surface of the dome is 20 inches apart. Does the "vent landing" start at this point? Or, does it start at the point in the middle of the landing where the radius of the inner surface would've intersected?

Or, is the size of the vent landing irrelevant, so long as you can install an 8 inch flue?

i initially sized my dimensions by comparing to the Pompeii oven instructions, ' but now, I am a little concerned that I've made the space in front of the oven for the vent landing a bit too tight.

[JRPizza]

Kid, without doing a layout I can't tell if the 20 inches you refer to puts the arch in the right location. It's important that your upper bricks fall within the curve of the dome so you can keep your shape round. Two easy ways to tell this - either do a full size layout (cad or paper), or place your arch form at the intended location, place a brick, and do some measuring from the center of your floor (I attached a cad snapshot and a view of a brick sitting on my form). There is some wiggle room here where you can move the arch in or out depending on how much room you have on your landing and if you want to use the arch to help support your vent (which is what I did).
As far as size of the landing go, it is good to have an idea of how deep you want before you get too far, as it is sort of what sets the distance of the center of your oven from the forward edge. It can't be too short to accommodate the size of the chimney, and if too deep it will be harder to reach into.

[Cameroonian Kid]

Thanks JR,

That is a big help. I'll get home and measure up - but I'm confident that I'll be fine having seen those pics.
,
In the pic's, how much overhang is tolerable? For example you show the arch brick with five "sides". In the diagram I've sketched what is the maximum value of "x" in relation to a normal brick, or can it only be zero?

ive also attached some pics of my build so far...

thanks again.

[Damer419]

Hi CK. I am just a few steps ahead of you and struggled with wrapping my head around the arch taper. This is the picture that Russel sent me that made the lightbulb finally go off in my head. To my understanding the Inner Radius of the dome should make the value of X from your diagram zero or close to it.

[UtahBeehiver]

CamK,

The X as D419 said should be 0 in a perfect world. this face is the inside diameter of the dome. The height placement of the pivot point of the IT will affect the X distance, ie if the pivot point is exactly at the floor level the X will be close to zero assuming the fore and aft of the arch is correctly places. You will need more the a half a brick for a tapered arch with the Top Dead Center arch brick being the longest (use a whole brick and cut down accordingly). I suggest you have the from of the arch brick protrude out front so you have a better tie-in point for your vent/chimney arch section.

[JRPizza]

First, I should have mentioned that the diagonal line on the right side of the brick in my first picture was drawn in error
If you look at my second picture, you can "see" that the brick could be moved in and out of the oven giving less or more protrusion like Russell is talking about. More protrusion gives more brick to tie in your arch and more room inside your oven. I don't think you can move the brick too far forward though (making X=0) as you need room to inscribe the inner radius on the arch brick as shown in my first picture. If I had moved the brick much more to the right I would have a "step" above the arch where the radius was not continuous.

[Cameroonian Kid]

Thanks so much for all of this.

I've realised that I need to bring down the sides of the arch and redo - they are slightly different depths...

Thanks again.

[JRPizza]

That's a bummer, but easier to fix now than later. It looks like you can just use the forward part of your floor to set the proper distance from the oven centerline, so hopefully the recovery will be relatively painless.