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Monolithic dome vs pre-cast facetted dome.

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  • Monolithic dome vs pre-cast facetted dome.

    I (as we all are) am considering building a pizza oven. I want to use refractory concret for its construction. I think I can make either a monolithic dome or cast parts and get a segmented dome.

    If I do a monolithic (single piece) dome I would create a sand form with a vertical rod that 1/4 arched-shaped piece of ply wood could rotate around to shape the sand form and then a wider one to guide the concret shape and thickness (using a thick peanutbutter consistancy mix to help keep it from slumping).

    If I cast pieces I would make molds and base it on a modified hexayurt (google hexayert for many examples) (truncating the top so it doesn't rise to a point) producing a structure with six sides and a flat top. I have made several miniture paper models of this and will produce a full size model when I have time to get the angles correct.

    Any thoughts?

    I think the monolithic dome would be the least work, and the fastest to construct.

    For a monolythic dome should I aim for a near perfect hemisphere or should it be more squat? Is there an ideal ratio for height vs width, like there is for the opening height (63%)? If I cast a solid dome should I cast groves into it to controle cracking (like a sidewalk)?

    If I make wooden forms can I just line it with plastic wrap instead of using a releasing agent and prevent moisture loss into the wooden form?

    Thank you,

    Mark

  • #2
    Re: Monolithic dome vs pre-cast facetted dome.

    Hi Mark,I am interested in doing something similar. I want my oven to be built on a trailer so I can have a mobile pizza business. I am still looking for as much info as I can get on this subject. I have seen a oven that I'm interested in but can't quite figure out what they used to build it. The business is out of Seattle,Wa. Veraci Pizza. Do you have any photos you could share?

    Thank you,
    Carol

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    • #3
      Re: Monolithic dome vs pre-cast facetted dome.

      Don't forget expansion joints!
      View my pictures at, Picasaweb.google.com/xharleyguy

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      • #4
        Re: Monolithic dome vs pre-cast facetted dome.

        I can appreciate that you want to do this 100% by yourself, but looking at it from a cost perspective standpoint, the money you would spend making forms, casting the pieces, and finding what does & does not work, I feel you would probably be way farther ahead if you were just to order the cast deck & dome components from Forno Bravo, and assemble them yourself. since they have already engineered an excellent product and are making it available to guys like us in component form to assemble onsite.

        Maybe you could pour your own deck or lay bricks, then fit a Forno bravo dome onto it so it is not a complete scratch built oven, but something you still have created?

        I am not trying to pee in your wheaties with my comments, I am just looking at the financial involved with the trial & error with this.

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        • #5
          Re: Monolithic dome vs pre-cast facetted dome.

          I build brick coal pizza ovens. You can look at my website:

          * Paving Stones - Monroe Township, NJ - Amato Quality Construction

          If you have question or want to discuss a project all of my contact information is on the site.

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          • #6
            Re: Monolithic dome vs pre-cast facetted dome.

            I think the effort involved to make moulds for multiple pieces for a one off is not worth it. A one piece dome will work and actually has advantages, especilly if you want your oven to be mobile. I would strongly recommend including stainless steel needles in the casta ble for reinforcing. The easiest way to make the sand dome to cast against is to place your stick in the middle as you stated, then just shape the hemisphere by eye. You will be able to get it remarkably accurate this way. Just tap the sand, with the flat of a brickies trowel, while viewing the profile with your eye. When applying the castable work from the bottom up and again just estimate the thickness as you go up it is quite easy. Use plastic to stop the castable fromsticking to the sand to give you a nice smooth finish on the inside. Actually I used pieces of damp newspaper because plastic will leave you with creases where it folds over th compound curve.
            Kindled with zeal and fired with passion.

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            • #7
              Re: Monolithic dome vs pre-cast facetted dome.

              Thanks to all for the advice. I am pretty sure I will build the one piece dome as that was what I had planned on doing in the beginning.
              Will post pics of my process but it won't be for several weeks.
              Carol

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              • #8
                Re: Monolithic dome vs pre-cast facetted dome.

                I have seen a steel barrel cut in half length wise and used as the inside of the dome then insulated. Will the thickness of the steel be thick enough to hold up to that kind of heat?
                Any help is welcome.
                Carol

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                • #9
                  Re: Monolithic dome vs pre-cast facetted dome.

                  Another Question:
                  Is concrete or cement better to use in building a M form over a sand form. From what I have read cement is stronger than concrete especially if movement will be envolved. I would live to apply by hand over the form (NOT POUR).
                  HELP

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                  • #10
                    Re: Monolithic dome vs pre-cast facetted dome.

                    Carol,
                    Be extremeky careful if cutting an oil drum in half. Using an oxy cutter, plasma cutter or angle grinder, all will create sparks. Many oil drums have exploded from the volatile vapours left from the empty drum and people are killed. It is a relatively common accident. Wash the drumm REALLY well with detergent first. On the Q re cement/ concrete. Cement is the powdered stuff, concrete is the mixture of powdered cement,sand and aggregatee. Can you rephrase your Q?
                    Dave
                    Kindled with zeal and fired with passion.

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                    • #11
                      Re: Monolithic dome vs pre-cast facetted dome.

                      Dave,
                      Thanks for the warning. I would probably buy a new drum.
                      Carol
                      Last edited by doughforthesoul; 03-01-2010, 09:54 PM.

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                      • #12
                        Re: Monolithic dome vs pre-cast facetted dome.

                        Carol,

                        Refractory concrete mixes are generally sold ready to mix with water. There are homemade concoctions, but they are said to be hard to work with.

                        That was what Dave was politely saying about rephrasing the cement/concrete question. Maybe some specific links to the products you are considering using will get a more specific response. It's way out of my realm of expertise.
                        My geodesic oven project: part 1, part 2

                        Comment


                        • #13
                          Re: Monolithic dome vs pre-cast facetted dome.

                          Originally posted by doughforthesoul View Post
                          I have seen a steel barrel cut in half length wise and used as the inside of the dome then insulated. Will the thickness of the steel be thick enough to hold up to that kind of heat?
                          Any help is welcome.
                          Carol
                          From my experience with mobile BBQ cooking equipment, I would need to say no way. that thin gauge steel would burn through rather quickly.

                          One of my mobile cookers has a firebox made from cold-rolled 1/4" thick steel, and that is getting quite thin in some places after only 2 years of use, one day a week only, for four months of the year, and at much lower temperatures then are common with a WFO.

                          Think of a trash burning barrel, look at how quick those burn out, I think the short lifespan also has to do with the trace amounts sodium hydroxide (Lye), produced, it is a natural component in the ash from burned hardwoods and it eats steel very effectively.

                          Now if you were to use the thin metal from a steel drum as a form, when it burned away you would still have the masonry work for our oven in place.
                          (I'm thinking out loud here)

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                          • #14
                            Re: Monolithic dome vs pre-cast facetted dome.

                            Carol,
                            If you go to a refractory supplier they will supply you with a dry product which has the refractory cement ,aggregate and other stuff mixed with it. All you have to do is add water and mix it, apply by hand over your form. The stuff sets quite quickly so do not mix more than about 20 Kg at a time. Then mix up a fresh batch and continue. The amount of water and temperature are much more important than that required for a normal concrete mix.
                            Kindled with zeal and fired with passion.

                            Comment


                            • #15
                              Re: Monolithic dome vs pre-cast facetted dome.

                              I am so glad I found this forum! Opinions needed.
                              Which material do you think is best for a mobile pizza oven?
                              Ferrocement with addition of fire clay or Refractory Concrete.
                              Thanks for all the imput.
                              Carol

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