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Some things that helped me and other thoughts - Forno Bravo Forum: The Wood-Fired Oven Community

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Some things that helped me and other thoughts

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  • Some things that helped me and other thoughts

    Some things that helped me during the wood fired oven construction and planning process.

    Number one - This site rocks and without it I don't know that I would have commited to the build.

    Other help.

    I found a local, foundry supply, company to provide the two inch rigid insulation board that the oven sits on. I opted for a two inch thick, calcium silicate material and since the supply company gets these in four by eight foot sheets, and they cut it to order, I was able to lay the board on the flat concrete support slab and had a dead flat platform for the oven to be built on. Forno Bravo, FB, sells two by four foot boards, three come in an FB kit, but I felt that the advantage of the larger sheet was that the oven and oven entry sits on fewer larger pieces of this board. I was able to I see the material, pick it up and get it home just when I needed it. From a four foot by six foot sheet, I was able to cut the sub base for the oven and an inner door and still have a bit left over. If I were to do it again I would buy a single four by eight foot sheet and only use two pieces under the oven and entry area. This would allow me to have one or two spare door blanks. Using larger sheet sizes wouldn’t have made any sense if I didn’t have a local source, but I did. If I built again and had to order the materials to be delivered, I’d order four FB boards just to have the flexibility that the extra material provides.

    This is more of a curious aside than somthing that helped. As far as entry design, I’d have liked to have further explored an integrated inner door. If the 20 inch wide entry into my dome is maintained but one or two hinged doors provide closure, then the advantage would be that these very hot door/s can swing out of the way and are quickly and safely available. Features like a thermometer, fiberglass gasket material and windows could be integrated into doors without too much trouble. The expense of this sort of thing is another matter. This sort of door / frame structure would mandate a larger entry area to allow the doors to open to an “out of the way” position, but the additional width would still be within the oven’s, structure, footprint. Other advantages would be that these door structures could be produced and therefore not necessarily as expensive as a “one-off” door. Dome and entry integration could be straight forward and less time consuming. The Dome / Arch integration was challenging and personally rewarding, but I would have considered an integrated door / frame if one were available. This would have left the arch building for the visible outside entry only.

    I bought the cleanest fire bricks available and I’m happy I did. These bricks were consistently flat and clean, so the oven floor is flat and tight as is the inside dome and entry surface. I had considered using lower cost bricks but decided that ten cents a brick didn’t warrant the irritation of cracks and uneven faces.

    I didn’t use home-brew mortar because I didn’t want to change mid-stream, but I have no doubt that home brew is what I’d use next time. After all, whatever you use, you have to adjust the mix to get the consistency you want anyway.

    I built a tool to allow me to consistently cut the brick cheeks based on brick slope angle and the radius of the course being placed. For me, I’d do it all again in a minute. I’d build the tool stronger not because the first one failed but because stronger would allow me to cut faster and more accurate and ultimately pass it around to friends and family. I’d also build tool to cut the horizontal bevel. This tool would be simpler since these cuts don’t change from course to course.

    Hendo’s tool is a must for brick placement but it does make the cleanup of the dome interior a bit more difficult. This tool is a no brainer must-have in my book.

    I used Rockwool insulation in direct contact with the exterior of the dome and entry, and it works great, but the two inch bats, soft boards, didn’t easily conform to the dome shape. The Rockwool price is right, and if I could find it as loose material, soft bats or blankets, I’d have no hesitation in choosing Rockwool again. The FB blankets are a more elegant, better, solution to direct contact insulation of the dome, but more costly. I used fiberglass attic bats as the second tier of insulation. These fiberglass attic bats have the advantage of being able to be easily tucked into the odd shapes of the interior of the oven enclosure and provide support for the primary, Rockwool in my case, insulation. Lastly I used vermiculite poured over the top of the other insulation. I had it around and felt that it would work into the voids around these other insulations. After all of this insulating, I have more than 72 hours of cook able time after a pizza session.

    I’m delighted and amazed by the performance of the stainless steel 8” Duravent Chimney. I can place and hold my hand on the exterior of the chimney pipe during a large fire without discomfort, and this is comforting relative to safety. These chimneys are very costly but worth it for me.

    Lastly, this oven seems to have established Sunday dinner as a special meal. Often we have family and friends over on Sundays and the oven is a major reason why. I’d commit to build it again in a heartbeat.

    Thanks James, and everyone else who makes this site run.

    Chris
    Last edited by SCChris; 01-15-2010, 02:17 PM.

  • #2
    Re: Some things that helped me and other thoughts

    Hey Chris, thanks for the info you addressed a couple of things I was thinking about.

    Comment


    • #3
      Re: Some things that helped me and other thoughts

      Hey Chris, Great analysis of your build, Im curios though,,
      I didn’t use home-brew mortar because I didn’t want to change mid-stream, but I have no doubt that home brew is what I’d use next time.
      Is there any reason beside cost ? What brand did you use ?

      Thanks
      Mark

      Comment


      • #4
        Re: Some things that helped me and other thoughts

        I used SairSet, a pre mixed mortar. I know pre-mixed mortar isn't looked on fondly by some of the knowledgeable folks around here. I found it to be workable and relatively easy to cleanup after and not overly expensive. All of this said, I still needed to mix it to the correct consistency and it was something that I had to make sure that I didn’t run out. The question that you may have is why you chose this product. The answer is way back I did some kiln work and when I started this project this kiln work was my reference point. I knew concrete has problems with heat and I knew that the oven was going to get hot so kiln mortar was further into my comfort zone than was premix. I now know concrete will start to break down somewhere around 1800F not the 1200F or so that we get our ovens up to. So, I got smarter with regard to concrete based mortar in WFOs. I don’t feel that the premix is really going to be a problem but I don’t see the advantage either.

        Chris

        Comment


        • #5
          Re: Some things that helped me and other thoughts

          FWIW, I used SairSet, too. At this point I have no regrets but ask me again in ten years. I think it was a huge advantage...loved that I didn't have to mess around with mixing up mortar every time I wanted to spend an hour or two setting bricks and that it was easier to clean up vs. a cementitious mortar. I didn't find that the consistency straight from the pail was an issue.
          Unless I see some major reason why it was a bad choice, I'd definitely use it again.

          Comment


          • #6
            Re: Some things that helped me and other thoughts

            I used the heat stop 50, Other than overly expensive I liked the fact that it took away the unknown factors in mixing my own... I would definitely use it again...

            Cheers
            Mark

            Comment


            • #7
              Re: Some things that helped me and other thoughts

              For all but a few, everything about their WFO build is new knowledge, and that’s where the comfort zone kicks in. Some things, like building a WFO, are a leap of faith, trust that it will get done and it’ll all be fine in the end. Mortar is one of those materials that you have trust and then get use to using. I was happy with the Sairset, at least to the degree that I trusted it and got use to it while I learned the mason skills.

              Chris

              Comment


              • #8
                Re: Some things that helped me and other thoughts

                Hi Chris,

                Were you able to find Sairset locally in OC?
                George

                My 34" WFO build

                Weber 22-OTG / Ugly Drum Smoker / 34" WFO

                Comment


                • #9
                  Re: Some things that helped me and other thoughts

                  Ardvark Ceramics in Santa Ana caries it, but you might find it at Foundry Service in Santa Fe Springs. Foundry Service has insulation board in large sheets up to 2.5 inches thick. Pacific Insulation might also have it, this is where I found the Rockwool although White Cap also carries Rockwool for placement around fireplace flues. If you go the Sairset route try to get a fresh batch, one of the batches I had was usable but old. It was a bit crusty on the top but mostly freed up with mixing. I used an electric drill with a thinset mixer attached. Run the drill forcing the mixture into the bucket, it's cleaner that way.

                  Chris

                  Comment


                  • #10
                    Re: Some things that helped me and other thoughts

                    Thank you Chris for the info. I will definitely check with Foundry Service as they are not too far from where I live.
                    Also, I was originally thinking of using vermiculite/perlite under the oven but the 1 piece 4x8 board looks very appealing.

                    George
                    George

                    My 34" WFO build

                    Weber 22-OTG / Ugly Drum Smoker / 34" WFO

                    Comment


                    • #11
                      Re: Some things that helped me and other thoughts

                      FXpose,
                      The board is what I did and I'm not unhappy about it. I spent $200 for a 4 by 6 2" sheet cut 52" by 48" and 20" by 48". The 52" by 48" underlays most of the oven I cut the 20" by 48" down to 20" by 26" and the remaining 20" by 22" became the door. I timmed the material with a table saw and a circular saw without issue. Just take care to avoid breathing the dust, wear a mask. You might check Pacific Insulation for prices on this as well.

                      Chris

                      Comment


                      • #12
                        Re: Some things that helped me and other thoughts

                        If you go the Sairset route try to get a fresh batch, one of the batches I had was usable but old.
                        This is a constant problem with pre-mixed mortars. They don't have much of a shelf life, and the retailers don't have much incentive to throw out the outdated inventory.

                        Mind you, the same thing can happen with dry mixes. I had to toss a few lumps from atmospheric humidity in my dry mix refractory mortar.
                        My geodesic oven project: part 1, part 2

                        Comment


                        • #13
                          Re: Some things that helped me and other thoughts

                          In the end I envisioned that the dome was just an organized pile of bricks always falling into itself, and so the main job of the mortar is to act as a caulk between bricks. I know that this view is a bit simple minded, and the mortars "glue factor" is important to hold the bricks together and direct the lateral forces downward into the base structure. Dmun had a link to the science of arches, fun reading, for me, thanks Dmun!

                          Chris

                          Comment


                          • #14
                            Re: Some things that helped me and other thoughts

                            I used Sairset as well for the majority (until I ran out and my source couldn't resupply for a couple weeks). I also used #1 Arch brick so I minimized the 'between-each-ring' joint thickness. One advantage to the Sairset was the fact that it 'takes a set' quickly minimizing some of the support needs. I finished up with Super 3000 and never took a good 'set' - it felt more "oozie", like sticky toothpast that would just get thicker. Super 3000 left me having to use sticks to support the brick.
                            To reduce costs, I would butter the ring-to-ring faces and tamp in place with a little 'twist'. Anchored the brick well. Try to pull a brick up and it would be stuck in place as if held by a slight vacuum. I minimized the Sairset usage between brick in each ring by buttering a blob at the hot-face joint. The Sairset would extend from the hot face back between the two bricks about 1/2 - 1 inch. The balance of that 'wedge' shaped joint I filled with home-brew mortar after I laid a complete ring of brick.
                            Worked nicely. I stood and jumped up and down on top of the dome when I had it done. The Arch brick mean the oven will probably be standing long after I've gone to the big bakery in the sky.

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