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32 Inch (800mm) Homebrew WFO in NS

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  • 32 Inch (800mm) Homebrew WFO in NS

    Hi!

    Like a lot of the threads, I have been reading this for a while and am now getting ready to start my own oven. I have one quick question before I post my plan for critique.

    Is it preferable to cast the dome on top of the fire bricks, or outside of the bricks with a small gap?

    Thanks for any input!



  • #2
    The true experts will weigh in, but I think both ways are good. The key is to have the entire oven (dome and floor) thermally isolated with the use of insulation. You can do that with the dome resting on the floor, or with the dome surrounding the floor. Probably comes down to whichever is easier for your build.

    In my personal experience, assuming you're building a hemisphere oven, I think it's better to err on the side of the top of the dome being too low, rather than too high. One oven I built had a high dome (higher than the radius), and the lower walls and floor take longer to heat up as a result. My recent build (in progress) puts the dome around the floor for that reason, so that the top of the dome is a little closer to the floor. Probably not a huge difference, but something I learned.

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    • #3
      Click image for larger version

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ID:	438749Thanks for the reply!
      I am going to try attaching my current plan view. It is currently a bit rough, but is being refined as I go!

      I am planning on reducing the gallery size, I will be browsing through some of the other threads on what an ideal gallery size would be.

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      • #4
        Some updated on my build:

        We an an big old ash tree in our back yard, that unfortunately was nearing the end of it's life. We had it cut down and ground down the stump. The location it opened up in front of where the stump was, turned out to be great for the oven. Except for all the roots that were still in the ground. With an axe, reciprocating saw, shovel and a farm jack I dug down as deep as I could get (not very deep!) and hauled out the major roots, and filled the hole back up with stone. We poured a 14cm (5.5") thick slab for the base, reinforced with 15m rebar.

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        • #5
          I don't have many pictures from building the block stand. I discovered that I am a very bad brick layer. We managed to get the stand in decent shape, but my mortar consistency needs some work! The stand is 8" CMU's.
          We formed up and poured the counter today. I inserted some pvc conduit in the corners to give me the option of anchoring in some framing later on down the line. I am planning on having a brick face enclosure, likely with steel siding on the sides and back, and a steel roof. I just have to sharpen my brick laying skills.
          I will let this counter cure for about a week before I take the side formwork off, I will likely leave the bottom form work for a at least 2 weeks if not the full 28 days, I don't think it will be in the way.
          Now I have to continue to refine my design, the gallery is definitely the part I have the toughest time visualizing.

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          • #6
            I have a question regarding the typical chimney if anyone has thoughts: My original plan was to use an insulated 6" inner diameter (8" outer dia.) stainless steel flu pipe. Does that give me much advantage over a single wall flu? I think the single wall flu would make constructing the gallery easier. Unless I am just thinking about the design wrong. The flu will be going through a steel roof. Thoughts?

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            • #7
              One other question I have after reading through this build: https://community.fornobravo.com/for...andpoint-idaho

              Am I ok to just have the Foamglas directly on the concrete counter, or is it worth using glass/ceramic tile underneath it? I see it was used in this build but don't see any further update on how it worked out.

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              • #8
                I have an opportunity to get a 5" (id) 7"(od) stainless steel pipe, about 5 ft high. It would be at a good price and include a cap. But it seems like 5" might be undersized for a 32" oven? Anyone use a 5" chimney with a 32" oven?
                Haha, I think I already know the answer... get a 6 inch chimney pipe.

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                • #9
                  Here are a couple more photos of my current progress. My base insulation is in place, 4" of Foam Glas Block topped with 1.5" of Vermiculite/Perlite (5:1). The Verm/perl has been curing and drying out for a week. my moisture meter still says about 1.3% moisture so I am going to leave it for a bit longer.

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                  • #10
                    Why don't you post where you got your vermiculite/perlite as well as FoamGlas. we get questions all the time where Canadians can get these type of materials. I did use FoamGlas in my build and since it does not absorb water is a great layer next to the concrete hearth. Cons, a little brittle and does not like abrasion. The newer versions have a lower working temp of around 800 F but you will not see this temp under the floor. Wait as long as possible before laying floor brick, once the pcrete is covered this is the hardest moisture to get rid of.
                    Last edited by UtahBeehiver; 07-10-2021, 12:22 PM.
                    Russell
                    Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]

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                    • #11
                      Good idea, some material sources for anyone in the Maritimes:
                      Shaw Brick is a source for firebrick and during the summer months also can provide fire clay.
                      The Perlite and Vermiculite can be sourced at some of the garden centers, mine came from Halifax Seed and Lakeland Plant World.
                      I sourced my pp fibers at Arrow Construction in Halifax.
                      Hope that helps! I have seen a few maritime builders in here.

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                      • #12
                        Getting ready to make the home brew and cast over my sand dome, I do have it covered in newspaper now.

                        I am wondering if it is ok to cast the dome, and cast the gallery 4 or 5 days later? My timing would line up like that, I am just wondering if it matters for better or worse if there is a prolonged period between casting the dome and gallery... thoughts anyone?

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                        • #13
                          4 or 5 days should be ok. But as you still need some moisture in the casting when filling the voids and the casting itself should be damp cured for at least a week, it would be wise to cover it.
                          Kindled with zeal and fired with passion.

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                          • #14
                            My dome is cast, thanks David S for the response. I have covered the dome with a plastic sheet. I believe that I do not have to spray any water on the dome? The plastic sheet is full of condensation already, I am guessing that is sufficient?
                            I am hoping to remove the sand and patch any voids after 48 hours. I am then going to try to get a gallery form in place.
                            Click image for larger version

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                            • #15
                              slainte , I am thinking of building a 32" oven as well and am wondering about casting the dome on top or around the brick floor as well.
                              What did you end up doing and how is the oven performing (I assume you finished it?)
                              Also, how big did you end up making your gallery, another question I am thinking about
                              Thanks

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