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Dome height/width and stability

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  • Dome height/width and stability

    I am about to start working on my dome. The door height is 21.5 cm, so my dome height should be around 34 cm (if I use the 63 % ratio). The dome width is 90 cm, so my concern is that the height won't be sufficient to hold the structure. I am using 5 cm firebricks, and it is 15 cm high at the sides, so total build of the cylindrically shaped part of the dome would be about 19 cm. Any thoughts to whether or not this will be ok? Any feedback is much appreciated. Oven will mainly be for bread, but pizza as well, of course...

  • #2
    Well, as there were no replies I went ahead and made a template for my dome. I will be doing a 60 % door/dome height ratio instead, which I hope will do just fine....It's not too late yet, so let me know if you see any potential issues or have any general comments

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    • #3
      Morning Bread,

      Welcome to the forum. Sorry for the lack of replies. Most ovens builds on this forum are Pompeii "hemispherical". There are a few successfull barell vaults that have been chronicled on this forum. You may want to do a search for "barrell vault". I had to do a conversion for the dimensions and It looks like you are wanting to build a low dome barrell vault. I don't have any first hand experience with barrell vaults. But, I do know that the high sides and low domes exert extreme outward forces. Those forces have to be countered by buttressing. From what I've seen, it is difficult to buttress without comprimising insulating quality.

      In a Pompeii, a lot of folks include flattened inner arches such as yours. But, in a Pompeii, the inner arch is buttressed by the dome. That is not the case with a barrell vault. So, you will need to include buttressing for it and the entry arch as well.

      Converting your numbers: An 8.5" (21.5 cm) door opening height seems mighty low to me. The 35" (90 cm) inside width is ok imo. If it were me, I would make the oven arch more hemisherical. Raising it up to 17.5" (44.5") would allow you to raise your door height up to 10.5" (26.7 cm). Also, still needing buttressing,but the dome would not exert near the outward forces as the low dome design that you have presented.

      I hope this helps.....................and.............please.. .......anybody............check my math .
      Joe Watson, "A year from now, you will have wished that you had started today"
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      • #4
        Originally posted by MorningBread View Post
        Well, as there were no replies I went ahead and made a template for my dome. I will be doing a 60 % door/dome height ratio instead, which I hope will do just fine....It's not too late yet, so let me know if you see any potential issues or have any general comments
        h

        I agree with Gulf, reviewing your photos I do not believe your chances of success are very high. As stated the arch is very flat and will require a lot of side support, which from your photos will not be available. The close flat roof design is more suited to a specialist pizza oven. Secondly barrel ovens are notorious for inconsistent temperatures around the oven and the low roof will present problems for baking bread without burning the tops and the door will make moving bread about to accomodate the inconsistent temperatures very difficult. In my opinion you need to rethink the entire concept.do not build an oven to suit the door. Having said all that I admit to building a Pompeii style oven

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        • #5
          An alternative to buttressing is to use some steel bracing around the oven. Search "barrel vault ovens" or "half barrel vault" for examples. Many builders decide to go for a barrel vault instead of a dome because they think it'd be easier to build. In fact because of the inherent instability and the expansion and contraction, it requires either or both buttressing and bracing which ends up making it a more difficult build. The Romans have been building hemispherical domes for a few thousand years because they found it to be the best all round solution.
          Kindled with zeal and fired with passion.

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