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Venting Vertical to Ctr of Dome - Forno Bravo Forum: The Wood-Fired Oven Community

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Venting Vertical to Ctr of Dome

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  • Venting Vertical to Ctr of Dome

    Team,

    I need help. I'm novice at buiding the oven and need some/lots of help.

    Iím building a 42Ē Pompeii (it's all done and looking good) and now designing the venting. My venting will start above the outside of the oven entrance and will traverse outside of the dome to the center of the dome and then up vertical.

    This design will require two Dura Tech elbows; one at the arch and one on the center of the dome. The issue is cost. The Dura Tech 30 degree elbows run $200+ each, are there more cost effective elbows that I can purchase that will suffice the requirement for a flue design? Also, what about effective venting/draw in my design?

    Thank you for any help/guidance you can provide me.

    Cheers,

    Domenico

  • #2
    Re: Venting Vertical to Ctr of Dome

    The engineered chimney systems are expensive, compared to flue tiles, but they are lightweight and can be secured to the structure without additional bracing for an offset flue like the one you're planning. It all comes down to a cost/time tradeoff like so many things in life. If your centered flue structure is some kind of structural masonry like brick, it will be fairly easy to add supports for the flue tile. If your superstructure is a lightweight metal stud with wonderboard construction, you should probably spring for the flue system.
    My geodesic oven project: part 1, part 2

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    • #3
      Re: Venting Vertical to Ctr of Dome

      Thank you for the reply.

      I followed the FB plan exclusively. I have the arch built with recommended firebrick and structurally it is very sound.

      Are you suggesting that I have the option in using a tile flue? I didnít know this was an option. I plan to enclose the dome with walls constructed with metal 2x4 studs all around so it is very possible to add additional studs in the interior as a way to offset the added weight of the flue and chimney components. Are tile flues and necessary elbows and stuff available?

      Thank you,

      Domenico

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      • #4
        Re: Venting Vertical to Ctr of Dome

        Sure, flue tiles are available at any brickyard. The 8 x 8 size is what you need. They come in 24 inch lengths, and are attached to each other with a refractory cement like heat-stop. There are no elbows: if you need a bend, you cut an angle with a diamond blade in your angle grinder. I'm not going to pretend this is a fun process. The flue tiles are very heavy, you are probably going to need some kind of support beyond the flimsy interior metal studs. You can see what I did, on my linked project page (I think the flue is on part two) and I had only a small offset. I actually built a reinforced concrete bridge over my dome, but this was to support the two story masonry chimney I built.
        My geodesic oven project: part 1, part 2

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        • #5
          Re: Venting Vertical to Ctr of Dome

          Wow! You did a great job. No way I can accomplish thi. I think I'll go the expensive route.

          What do I build on the top of my 6”x10” opening in the arch for venting? Do I build a rectangular box using firebrick so I can attach my anchor plate? How high should I build this and how do I attach the Dura Tech anchor plate (e.g. anchor bolts are each end and heatstop)?

          As you can see I am very novice on this flue, flue liner and chimney stuff so please excuse my ignorance.

          I’ve been reading many of the post on the forum and it’s helped me a lot but still have some things I need help with.

          I appreciate your help.

          Thanks,

          Domenico

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          • #6
            Re: Venting Vertical to Ctr of Dome

            I tried to find it for you, but the forum founder, James, did an offset flue with the stainless chimney system, in an enclosure like the one you plan. Maybe James will jump in and point to the construction photos of his oven (the one you see in his avatar)
            My geodesic oven project: part 1, part 2

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            • #7
              Re: Venting Vertical to Ctr of Dome

              Awesome! I'll wait for James to share some photos. it's raining here in the SF Bay Area (Fremont, Ca.) but if it stops I'm planning to build the exterior arch and vent this weekend, so hopefully I can get some ideas before this weekend. Just received Refmix from FB to complete the final arch and a bit of interior gap cementing. I've attached pic of what the oven entrance arch (reveal) looks like.

              It would also be good to go into more details of the venting construction in the FB Pompeii Oven Plan. The FB plan was very, very good in the construction of the base, hearth and dome, including the arch, but lacked a bit of detail in the venting as it applies to the Dura Tech flue system.

              I appreciate your help and technical guidance. I'm almost there and excited to better understand how to construct my venting. I hate to screw things up at this stage.

              Thanks!
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              • #8
                Re: Venting Vertical to Ctr of Dome

                You may want to consider going another route. You could use KS-4 (or similar) and cast your transition piece. That way you can make it any shape you want. You could use it to go from the vent opening all the way to the top of the dome to mount you chimney to. I do not know if it would save you any $, it would take at least 2 maybe 3 - 50 lb bags ( I paid $50 each + $10 in stainless needles) and be a bit more work.

                It worked out well for me.
                Wade Lively

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                • #9
                  Re: Venting Vertical to Ctr of Dome

                  The reason that the venting instructions are vague is that builders use a multitude of building methods for the flue. It's true, though, that most ovens vent straight up from the mouth of the oven: This reduces the complexity by an order of magnitude. There are basically three elements: some kind of inverted funnel to channel the smoke into the flue, a length of stainless flue system or refractory flue tile, and some kind of enclosure to cover it up. Everything else is commentary.
                  My geodesic oven project: part 1, part 2

                  Comment


                  • #10
                    Re: Venting Vertical to Ctr of Dome

                    I’m planning to use clay liners as a way to get the angel needed to vent outside and uo center of dome. I’ll have to build a superstructure to support the clay liners…no problems.

                    Critical concern: I calculated the angle needed to vent towards the center of the oven to be 65 degrees. Is this angle too steep, which will affect draw efficiency? Has anyone on the forum done this? I’m still waiting for James to reply as I understand he has done something similar.

                    Thank you,

                    Domenico

                    Comment


                    • #11
                      Re: Venting Vertical to Ctr of Dome

                      Building code calls for a maximum bend of 30 degrees, in no more than two places. That's the sharpest angle you can get a flue cleaning brush through. WFO's tend to have short hot fires, and not accumulate creosote, the way that woodstoves do, so if this project isn't subject to inspection, you may be able to get away with a sharper bend. I have no particular experience though. We did have a member recently who had a 90 degree bend in the chimney who's kitchen was filling with smoke.
                      My geodesic oven project: part 1, part 2

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