Come on, Simone. Let's talk about your big butress.

[Zimmy]

Pee Wee Herman must have been mistaken, as not everyone here has a big butress. In fact most of the builds I see here do not have them.

I'm at the point with my arch design where I need to choose semi-circular or straight sides with a shallow arch. I see lots of comments about the straight-sided approach needing buttressing, but hardly anyone actually doing it. I must admit, I like the more refined look of three courses of vertical bricks with a shallower arch on top. But I am building a high dome/hemispherical igloo-style oven, so maybe a semicircular arch entry will better match the aesthetic of the design? And I am in SoCal earthquake country so strength to withstand movement is a real concern. I am not building an enclosure, so the extra bulk of butresses will really be noticeable. Let's discuss.

[david s]

Buttressing will increase strength (good), but also increase the heat sink effect (bad) that can be mitigated to some extent by separating the whole flue gallery from the dome.
Because the flue gallery sees lower temperatures than the dome, thermal expansion is lower which reduces potential damage. Brick galleries are more susceptible than cast ones because of their mortar separated units.
For these reasons I believe a cast gallery or fabricated stainless steel one are superior solutions to a gallery made using brick units.
But there are a myriad of solutions, largely determined by personal preferences.

[JRPizza]

You've probably already seen that I'm a fan of the hemispherical arch. Below I took the recommended dimensions for a 36 and 42" oven from the Forno Bravo plans and interpolated for my 39 inch oven ( roughly a meter and I think perfect size) as well as your 37.5
Your numbers would come out to about a arch opening of 19.25 inch wide and ~12 1/8 high. That width would give a natural radius of about 9 5/8.. If you start your arch radius sitting on top of a 2.5 inch untapered brick, you would get a opening of exactly 12 1/8 (not counting for thin mortar layer). You can build a flat arch if you want, but I think the numbers are trying to tell you something!

			Opening	Opening	Ratio
Inch	ID	Height	Width	Height
36	36	18	19	12	66.67%
37.5	37.5	18.75	19.25	12.125	64.67%
39	39	19.5	19.5	12.25	62.82%
42	42	21	20	12.5	59.52%

[JRPizza]

This picture kinda shows what I was trying to describe with the untapered bricks at the arch base and the arch radius starting at the top of those bricks.

[Zimmy]

Those tapered bricks look amazing. I don't think my wet saw is nearly big enough to cut in the 4-1/2 inch brick direction, so I'll have to go with wedges in my mortar joints. I do want to figure out how to make a nice oversized keystone for the top of the decorative arch, though

[Gulf]

You can cut part way through and then turn the brick over and cut from the other. It will probably leave a small section in the middle that is not cut entirely through, but a light tap will finish the job. I have done it free hand. However, clamping an angled guide to the tile saw will make things much easier.

[JRPizza]

I tried to walk through the process of cutting the arch bricks in my build thread - it was really not that hard and I think the look is worth the trouble. I had to flip the bricks over but was able to cut them all the way through in two passes. Just cut them all from one side, then adjusted the jig and did teh second pass. I also used the same angles for the inner and outer arches.

[Zimmy]

JRPizza I read through most of your build thread this evening to figure out how you cut the arch bricks. You show in post Adding a smoker a 3D printed jig for cutting your vent arch bricks. Did you also use same approach on your dome/inner arch bricks? The photos in post #42 show them clearly tapered.

Also, are your dome arch bricks full 9" length? It looks like you planned to in post #3 and it post #17 I see you trimmed to match both the dome ID and a taper to match the outboard bricks, so maybe still 9" to the tip of the corner.I'm currently planning on using full length bricks to prevent the dome from running away from the top of the arch (Called a beaver tail? Maybe that is the name of the solution), but am looking to reclaim any depth I can on the front.

[JRPizza]

Not sure where that link to "adding a smoker" came from but it does not point to my build.
My tapered arch bricks first appear in post #24 and I mentioned my angled shim in the post before it, but I don't show the shim/jig until post Adding a smoker I had so many things going on that I forgot to show it early on.
When I got to the bigger vent arch I figured out that I could use the same angle jig as I used for the inner arch - are the angles perfect, no, but it was close enough so the same angles on all the arches worked for me. I think I just added a brick or two (you would have to count in the pictures) and it all worked out. The keys to my jig were having the right angle for the narrow side of the brick to sit on so I could cut the taper, and a lip/stop so I could index the edge of the brick against to get repeatable cuts. I apparently lost the file I used to make my 3D print in a computer crash or I would send you a copy. I do have the angles (I think) somewhere if you want me to dig them out. I also have an arch angle spread sheet somewhere.
I cut all my bricks in the full 9" length. I found it easier to work with longer bricks - more to hold on to and easier to control. I trimmed them to appropriate length after tapering.
One thing I mentioned and found critical - some of my bricks did not have narrow sides that were 90 degrees to the wide side, the cross section was a parallelogram, not a square. I had to sort bricks with a square so when I had the narrow side against the jig I got uniform cuts.

[JRPizza]

I found the .stl file for my jig. If you don't have a printer you can get prints lots of places. Our UPS store does prints. Let me know if you want a copy.

[Zimmy]

Not sure where that Adding a smoker link came from either, but it did it to your post as well. When you say "I cut all my bricks in the full 9" length...I trimmed them to appropriate length after tapering." does that mean your dome arch was narrower than 9"? I do not have a 3D printer, but have friends with them. Can you e-mail the file to me? I'll DM the address.

[JRPizza]

The inner arch bricks are mostly full length, but have different bits cut off of them to fit the ID surface of the oven. Have a look at the link below where I had discussed this in the past and a few pictures that show the inner cuts. Remember as your arch approaches it's top, the dome is receding, so the arch bricks have to get "longer" to stay engaged with the dome.

https://community.fornobravo.com/forum/pizza-oven-design-and-installation/pompeii-oven-construction/430054-42-in-south-ga?p=435421#post435421

[JRPizza]

Here is a copy of my arch brick jig, in two different extensions - a .stl file and a .thing file. Not sure which one will work for you. You can't post these files directly, but if they are zipped you can.