36" Corner Build in Minnesota

[RandyJ]

JRPizza you are probably correct. Yes as long as it is thick enough and has rebar in it pretty much anything he wants to do will be just fine. With the poured arch there is plenty of support there.

Randy

[MnDude45]

JRPizza - I’ve been reading your post from another build and trying to recreate the scenario for my oven.

I have always recommended using CAD to help properly locate fore/aft placement of the inner arch, but if you are building a hemispherical dome oven with a hemispherical arch there is a simple way to determine location using any surface large enough to draw your dome inner and outer diameters in full scale. A large carpenter's square comes in very handy when using this method.

1. Using a marker with string, a large compass (bought mine at Harbor Freight) or your IT, draw two concentric circles representing inner and outer diameter of your brick dome.
2. Draw a line from the center of the circles out past the circle representing the outside diameter, which in my drawing is the lower horizontal line running to the left. This line represents the center of your vent/landing
3. Draw a line above and perpendicular to this line at a distance representing the height of your opening. This is a set dimension. In my drawing the line is at 12.25" representing the height for a 39" oven.
4. Now you can place a full size brick lying flat with the lower edge resting on this line, and move it fore/aft making sure it still lies in the area bounded by the dome ID and OD. If it does not properly intersect the dome you will have to go "out of round" to integrate the arch into the dome. The first and second picture show the extremes of fore aft placement. In the first picture the brick is in a more forward position, which provides for the largest interior cooking space, largest protrusion at the top of the arch to build your vent either on or over with a heat break, but also makes for a slightly longer vent landing. The second picture has the brick at a very rearward position. This can give the shortest landing, but cuts down some on the inner space in the oven and does not provide any protrusion for incorporation into the vent arches.
5. When you are happy with the fore/aft positioning of the brick, draw a line downward at 90 degrees to the horizontal line you measured your arch height from. Measure the distance from that line to the center of the oven, and you have the distance from the center to the front edge of your arch form. Build and shim your arch form so that the forward face is straight up and down (perpendicular to horizon) and if you index your arch bricks flush with the face the arch bricks will all be in the same plane and a door will have a good even surface to seal against.
6. With the distance from the center to the front of the arch set, you can now draw a similar perpendicular line at a distance equal to half the width of your door. I did this in the third figure at 9.75", representing half the width of my 19.5" opening. There are 2 bricks shown representing the most forward and most aft arch placements I looked at in the steps above. Lay the inner edge of a full size brick at the door width and position the forward edge at your arch forward distance. The the inner diameter circle now shows you the arc you need to cut on the bottom arch brick and will help you determine how deep you need to make the arch form. You can kind of see how wide to make the arch form. You should be able to index both the front and rear inner edges of the bottom brick (after trimming) against the arch form to keep the bricks in proper orientation fore aft and perpendicular to the centerline of the landing. This is what I was trying to show in the first picture of post #22 above.

My pics show are trying to show this but not sure it’s right. My main purpose now is to figure out the placement of the inner arch, the vent/outer arch and depth . With this said, I’m not sure where the arch face should be? Help!!

[JRPizza]

Are you following the FB plan recommended opening dimensions for a 36" oven at 12" high and 19 wide, or did you have different dimensions in mind? Also, are you going with an igloo look or are you going to enclose the oven?

[JRPizza]

The reason I asked if you were going to enclose the oven or go with a igloo is to see if you are constrained to having the center of your oven in the center of your corner or if you could slide it back to have more room for the landing if needed. The pic below shows how I moved my oven back on the slab as far as I could, where if I did an enclosure I probably would have centered it more fore and aft.

[JRPizza]

Back to your pictures. The center pic in post 32 is a great start but I think the lines to the right of the center line are not good. My instructions would have been clearer if #3 said "Draw a line to the right of and perpendicular to this line at a distance representing the height of your opening.", meaning there should be a line 12" to the right of the center line going towards the front of the oven. You would rotate the brick you have on the top right 90 degrees and see how the TDC arch brick will meet the dome. It's a drafting trick, but when you do that it is like looking at the dome from the side and the arch brick is "floating in air" if that makes sense. The stuff you are drawing to the right side of the center line represents a side view of the oven, where the lines on the left of center represent looking top down.

[MnDude45]

On your first questions, yes and enclosed. I’m planning on the FB standard 36” with opening of 12Hx19W. I am planning on enclosing the oven so I need to factor in the 5”in exterior cover of cement board and studs.

My pics are trying to recreate the pics from your previous post but tried to use the same 18” semi circle to view both the side view (pics 1 and 2) and the top view for pic #3. Now that I think about it, this assumption is bad because in pic #3 the distance for the center of the oven is not 18” but 19.1” due to the factor of IT being 1” from the floor. Ugh!

[MnDude45]

UtahBeehiver - this may be stupid question I’ve seen several people constructing the IT, which you were good enough to send to me. When attaching a pen/marker, is it a separate tool or an attachment to the same one used for constructing?

[UtahBeehiver]

Same IT, just replaced the "L" bracket with the pencil. The carpenter pencil holder is a plastic holder from the Orange Box store, I epoxied a nut the same thread as the all thread on my IT. And you can rotate it to scribe the arch bricks as you move. My IT, not knowing any better when I did my oven, had a pivot point off the floor elevation (thickness of a piece of 3/4" ply). Current school of thought is to have the pivot point at floor elevation. I would go the Gulf route and make a wood brick to fasten the IT to then when done remove the wood brick and install the firebrick.

[MnDude45]

Putting this here for my reference

Here is my IT, very basic but works well. Used a scrap piece of 2 x 4 fur and ripped it down to two pieces 1" x 1 1/2". Not thinking, I had 42" in my head and cut them to make a 42" IT which was an easy fix to cut off so they would make a 21" IT. Any way, picked up two 1/4" x 4" carriage bolts, flat washers, lock washers and wing nuts, cut 5/16s slots for the adjustment, added a small hinge that I had laying around and bent a 90 in a scrap piece of thin metal plate. I also used a piece of 2 x 6 fur which I cut to 4 1/2 x 9 and then put spacers under it to raise it to floor height.

[UtahBeehiver]

BTW, I am a big fan of a mono arch pour on the base. Nice job.

[MnDude45]

I took a stab at the non weld IT today. I need to find the right brick clamp/guide and a way to attach a pen/pencil/marker but I like the simplistic design from DWatkins.

[UtahBeehiver]

Just be aware that having the pivot point offset vertically as well as horizontally will require that you make adjustments at each course. Second, it is really important that the line projecting from the pivot point intersects the mid point on the brick thickness, ie 2.5" brick, center is 1.25". If you do not do this the brick faces will not be perpendicular to the center of the dome and the error is cumulative as you go up in courses.

[MnDude45]

I had factored in the need for the vertical adjustment but figured I could adjust the spacer on the base I use for the center brick. I hadn’t thought of your second point on the mid point.

[Ope-dog]

MnDude45,
Your build looks like it's off to a good start!! To echo Russell's point, there are different designs you can utilize, however be sure you leave yourself the proper "wiggle room" on your IT depending on which style you go with. I opted for a design that didn't require too much welding or cutting and has been used by various builds on this forum. Using a piece of all-thread with a turnbuckle allows the length to be adjusted accordingly as you start to go up in height. (To compensate for the distance between pivot point and floor base.) I actually tried to use JB Weld to keep my bracket and nut secured to each other and didn't have good success. Simple super glue ended up being more than sufficient, and I even found myself stressing the bracket much more than I should've been at times. My bracket was a simple 90 degree and I used a grinder to grind the nub off that was at the inside of the bend so it fit evenly along the edge of the brick. Measured down 1.25" and that was where I glued the center of my nut.

Not the best pic but I think you get the idea. Lots of folks blazed this IT method prior. Happy building!

[MnDude45]

Ope-dog Thanks for the input. I’ve been looking at a ton of examples of IT’s this week but I’m working on setting up my forms for hearth/countertops this weekend and hope to be pouring a bunch of concrete next week.