A few questions from Austin TX

[UtahBeehiver]

Here is one I show people all the time when they are doing opening like yours. It is from Mr Chipster and it also shows how the it is used to do an inner taper arch. The height of the opening of the arch should be abt 63% of the "radius" of the ID of the oven, IE 42" oven = 21" X .63 = 13.25. Width is user preference so 20" wide is fine.

[patjer1]

One question regarding the inner arch transition; with the IT I can draw a line with the inner and outer diameter of the oven and from then on the slope. Do you cut the bricks at that line or a bit lower, minus the mortar joint?
Greetings.

[UtahBeehiver]

Just cut on the line. You do not know at this point if these bricks will be in line with the joints on the dome. Each brick is slightly different. You start with the top dead center brick of the tapered inner arch the work your way down left and right of TDC and using the previous brick as a baseline for the next one in conjunction with the IT. You need to use start with whole bricks on a tapered arch not half bricks. If you want even joint lines, then you will need to taper the bricks first, place, then do your cutting for the tapered "inner" arch.

[patjer1]

Not a good idea to taper the bricks frist and then mark them layer by layer, cut them and mortar them? Without starting with the TDC brick I mean.

[Lagniappe]

I think I am finally starting to get it. Thanks so much for the explanations and pictures. I had actually seen some of these before and couldnt grasp the idea until I had bricks in hand.

Mocked up the bricks height at center of opening and 21" distance from center and snapped a couple pics.

If someone could take a look, would be great and let me know if you think I need to move the opening closer .

Either way, I will work on the form as suggested.

[UtahBeehiver]

Only a suggestion on laying out the arch first. I see it quite often where a builder builds the arch as they go and end up with an odd width, either too big or too small. Even though this is the inner arch that is not as readily seen as the outer arch, it will be good practice to get good spacing so when you do the vent chamber and outer arch you golden.

[patjer1]

Just cut on the line. You do not know at this point if these bricks will be in line with the joints on the dome. Each brick is slightly different. You start with the top dead center brick of the tapered inner arch the work your way down left and right of TDC and using the previous brick as a baseline for the next one in conjunction with the IT. You need to use start with whole bricks on a tapered arch not half bricks. If you want even joint lines, then you will need to taper the bricks first, place, then do your cutting for the tapered "inner" arch.

Think I got it now. You draw the lines with the IT on one side of the brick and on the other side of the brick you take the lines from the brick next to it? So the cuts are also in an angle,and not 90°?

[UtahBeehiver]

Right on, Then the bottom angle is the arch of the ID of the dome.

[Lagniappe]

So, I took most of the summer off from the build. Between summer travel, lots of work commitments, kids activities and almost every day in July over 100. just didn't have the time or energy. But I am back. I got 3.5 inches of vermicrete poured (used 5:1 ratio per all the posts i read) and bought four sheets of 2" ceramic fiber board from FB. Prior to my break, i had already cut the floor bricks. So looks like next step is to cut the fiberboard, level, and get started on my first course. Here is where I could use some help:

What is the best way to cut this ceramic fiberboard? Seems like i can just break off a corner, i cant imagine how it cuts cleanly.
I see lots of pictures of it being cut in a circle to match the outer diameter. I plan on doing an enclosure, can i just leave it square or is there an advantage to cutting it into a circle?
For leveling - sand? Fireclay? Mix?

Thanks a lot & look forward to making some real progress.

[UtahBeehiver]

You can cut cut with a jig saw, be sure to use a Niosh 95 mask. Since you are enclosing no need do to an exact fit. Just make sure it is wide enough for the dome walls and floor bricks. 50/50 sand fire clay mix.

[JRPizza]

I used my sawzall and a workmate type table that I could clamp the board down on. My board was 2.5 inches thick so I needed a longer blade. Make sure you note the wind direction and stand upwind when you are cutting and make sure nothing sensitive is down wind. I thought that was some of the nastiest stuff I ever cut, until I started working with the ceramic blanket for the dome

[RandyJ]

I cut mine with a hack saw blade just open in hand. I went fairly slow but it was as nice clean cut and not as much dust. But no matter what make sure you wear a respirator, and not a dust mask. It is some pretty nasty stuff.

Randy

[Lagniappe]

Thanks everyone.
I feel I made some progress.
Ceramic fiberboards are cut (used a respirator), OSB is cut to protect the floor bricks during install, wrapped some cardboard around the edge as an expansion joint.
Mocked up the start of my indispensable tool. Need to cut to fit, secure it to center point, and add the bracket to hold the brick. I know it is sitting on top of the OSB plywood and not at exact floor height and since using a caster, the pivot point isn’t perfect. Hope this is good enough, but all suggestions welcome.
Sand, lime, Portland and fireclay purchased for homebrew.
Any alarm bells from those of you with experience? If not, I plan to mortar in my first course next weekend.

[UtahBeehiver]

Just remember that the dome height will be the floor radius plus the thickness of the OSB and the height offset of the caster. This may affect how you tie into a tapered inner arch (if you go this direction - IMHO I recommend). It be hard to make radius adjustment with this IT since it is a solid piece of lumber. Couple things on the IT. first, the centerline of the IT must intersect the centerline of the brick face so you need the place the "L" bracket accordingly. Second, if possible, reconfigure the IT to be adjustable especially due to the vertical height offset from the floor.

[SableSprings]

Take a look at Atak's post #205 ( https://community.fornobravo.com/for...b-theme/page14 ) for his IT variation. You could lower your attachment point for the IT as Russell noted above and by using Atak's clamp version of IT, your adjustments will be much easier. Just some food for thought...