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Castable - How thin can you go? - Forno Bravo Forum: The Wood-Fired Oven Community

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Castable - How thin can you go?

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  • Castable - How thin can you go?

    Does anybody know how thin a dome can be cast and still work?

  • #2
    Re: Castable - How thin can you go?

    Gudday
    Difine "work" in relationship to "dome"

    Regards dave
    Measure twice
    Cut once
    Fit in position with largest hammer

    My Build
    http://www.fornobravo.com/forum/f51/...ild-14444.html
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    http://www.fornobravo.com/forum/f28/...ock-17190.html

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    • #3
      Re: Castable - How thin can you go?

      Probably depends on your castable, whether or not you are using SS needle reinforcement, the size of the cast pieces and method of placement. IMO 2" is ok if done properly. Also depends what you mean by failure. Hairline cracks, decent sized cracks? Because the dome is a self supporting structure, even if it cracks severely into a number of bits it will still stand up.
      Try making one half as thick as you dare and report back.
      Kindled with zeal and fired with passion.

      Comment


      • #4
        Re: Castable - How thin can you go?

        Originally posted by cobblerdave View Post
        Gudday
        Difine "work" in relationship to "dome"

        Regards dave
        1) Dome to maintain integrity through repeated heat/cooling cycles.
        2) Self supporting- at high temps for pizza making/low mass application.
        3) Self supporting- moderate temps-for breads/general oven use where "additional mass would be added" to outer surface of dome. But basically same dome as for (2)
        3a) Mass to be determined- right now unknown.

        4) Assumption- aside for additional thermal mass, no other weights need to be calculated, outer render to be precast--inner void filled with loosefill or ????

        A starting place anyway for this discussion.

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        • #5
          Re: Castable - How thin can you go?

          Originally posted by david s View Post
          Probably depends on your castable, whether or not you are using SS needle reinforcement, the size of the cast pieces and method of placement. IMO 2" is ok if done properly. Also depends what you mean by failure. Hairline cracks, decent sized cracks? Because the dome is a self supporting structure, even if it cracks severely into a number of bits it will still stand up.
          Try making one half as thick as you dare and report back.
          Thank you david s for checking in--by your threads you have experience in casting.

          I was hoping for something in 3/4" to 1" range. I suppose a parameter must be set for oven size to begin with.

          What size would be attractive to a small household- with 1 to 2 children?

          Something to think about, to gain strength.. would ribs or sections with a thicker cross section allow for thinner builds?

          A dome cast as a single section preferable.

          I would assume "a pourable type castable" preferable to trowel type. But pourable by design has larger aggregate. Assuming that many manufacturers have similar products. (trowelable AGC is OK min thickness 20mm).

          (The reason for even thinking about this is because I noticed how strong even a 6mm thick section of my render was today---I had to grind off some of my bad work, and the diamond cutter was singing to me--like it was hitting steel).

          Thoughts- thin, affordable, portable.

          This one-- think it through first, then make it! If it doesn't perform, adjust and try again. If the casting is thin enough, the cost is of little significance.

          Comment


          • #6
            Re: Castable - How thin can you go?

            Gudday
            Just a thought but most cast ovens I have come across are 2 in thick, in fact from what I know ,same again for the clay/sand shell of a cob oven.
            The forno oven a 1/2 brick 4in thick. Is this just the "overkill" that makes the forno oven a robust construction or just a convenient size being a 1/2 brick?

            Regards dave
            Measure twice
            Cut once
            Fit in position with largest hammer

            My Build
            http://www.fornobravo.com/forum/f51/...ild-14444.html
            My Door
            http://www.fornobravo.com/forum/f28/...ock-17190.html

            Comment


            • #7
              Re: Castable - How thin can you go?

              I thought someone made an oven using pavers, something like 1 1/2" thick. But these would be a bunch of segments, held together with a refractory mortar.

              I would like to imagine much thinner. Everyone knows how strong an egg shell is and how thin it is.

              Someone with some math skills should be able to predict at least a range of thicknesses--even though they are not commercially available.

              I thought I saw a thread about a rocket stove pizza oven that used a flower pot dome. Instead of looking for the best pot, I thought it would be better to design a dome with the proper ratios in mind. But just thinner than the conventional.

              It seems like the most difficult task is making a dome with the right dimensions to work. Additional mass can be added; different insulations used; and all the rest which I consider "decoration" added to suit the end user. (To clarify better-"an operating oven-including opening,landing,transition,chimney etc all included as proper design for dome). Design features I consider decoration-brick,stone,plaster,stucco,other cladding etc. These are reflections of the owners personality.

              Comment


              • #8
                Re: Castable - How thin can you go?

                Originally posted by mikku View Post
                I thought someone made an oven using pavers, something like 1 1/2" thick. But these would be a bunch of segments, held together with a refractory mortar.

                I would like to imagine much thinner. Everyone knows how strong an egg shell is and how thin it is.
                My question would be why would you want to? With a super thin shell you would have to have recharge your fire constantly to maintain temperature, even with good insulation. Also what advantages would you have by making a thin walled oven? IMO, nowhere near enough to offset the inefficiencies.

                interesting concept though.
                Old World Stone & Garden

                Current WFO build - Dry Stone Base & Gothic Vault

                When we build, let us think that we build for ever.
                John Ruskin

                Comment


                • #9
                  Re: Castable - How thin can you go?

                  Normally, concrete is getting dicey at at 3". Using additives and fibers you can get that down to an inch, but those are for non-refractory applications. I would say that less than 3" without SS fibers is pushing it for a refractory situation.

                  Comment


                  • #10
                    Re: Castable - How thin can you go?

                    Originally posted by stonecutter View Post
                    My question would be why would you want to? With a super thin shell you would have to have recharge your fire constantly to maintain temperature, even with good insulation. Also what advantages would you have by making a thin walled oven? IMO, nowhere near enough to offset the inefficiencies.

                    interesting concept though.
                    I guess main reason, portability.

                    Same reason for "Weber" type BBQ grills, people cannot always stay at one location forever or have the inclination to create monuments.

                    So a day at the beach could include baking a pizza, just throw the portable oven in the car along with the rest of the stuff... Get to your destination--assemble some KD parts--add some "mass" readily available--i.e. beach sand, stone rubble, whatever. Light it up with "twigs", heat beads, and enjoy.. When you leave, return the "re-usables" to their original location. Only difference, they got heated up a little once.

                    Same concept for renter or apartment dweller. Make your oven portable enough that you can take it with you when you relocate--like a favorite chair, TV, etc... that you and a friend can easily get into a car or pickup and set-up again at your new digs.

                    The point is "scale", why does an oven need to resemble a garage, interstate tunnel, stadium or cathedral with flying buttresses? Thought there would be some middle ground to explore so more people could enjoy a WFO.

                    I guess part of this discussion needs to define what are the essential components of a WFO?

                    Which traditional parts are superfluous and gaudy.

                    What would a bare bones oven look like? Its design should reflect its function.

                    Comment


                    • #11
                      Re: Castable - How thin can you go?

                      Originally posted by mikku View Post
                      I guess main reason, portability.

                      Same reason for "Weber" type BBQ grills, people cannot always stay at one location forever or have the inclination to create monuments.

                      So a day at the beach could include baking a pizza, just throw the portable oven in the car along with the rest of the stuff... Get to your destination--assemble some KD parts--add some "mass" readily available--i.e. beach sand, stone rubble, whatever. Light it up with "twigs", heat beads, and enjoy.. When you leave, return the "re-usables" to their original location. Only difference, they got heated up a little once.
                      What you are describing can already be done with a grill. And when you have something designed to be heated up to 700*-900* to do what you want it to do..and do it efficiently...then you will have to wait awhile before you throw it into your car and go home.

                      All that aside, masonry does not like movement, and if you factor in thermal cycles, a thin shelled portable oven wouldn't last very long.
                      Old World Stone & Garden

                      Current WFO build - Dry Stone Base & Gothic Vault

                      When we build, let us think that we build for ever.
                      John Ruskin

                      Comment


                      • #12
                        Re: Castable - How thin can you go?

                        Originally posted by mikku View Post
                        The point is "scale", why does an oven need to resemble a garage, interstate tunnel, stadium or cathedral with flying buttresses? Thought there would be some middle ground to explore so more people could enjoy a WFO.

                        I guess part of this discussion needs to define what are the essential components of a WFO?

                        Which traditional parts are superfluous and gaudy.

                        What would a bare bones oven look like? Its design should reflect its function.
                        Again, masonry has its limits when you add motion to the equation. You need mass when you are building with masonry...it is not a "portable" material. Is there other options besides one that are superfluous..yeah. Use a green egg or something similar...lightweight metal shell (relative to masonry) with a thin refractory liner.

                        I have never seen a WFO with a flying buttress, that must have been one heck of an oven..with a huge open space underneath.
                        Old World Stone & Garden

                        Current WFO build - Dry Stone Base & Gothic Vault

                        When we build, let us think that we build for ever.
                        John Ruskin

                        Comment


                        • #13
                          Re: Castable - How thin can you go?

                          Originally posted by wotavidone
                          Or there is the "Big Green Egg" thing. I've never seen one of those, I guess you must be able to move them?
                          Even the small one is heavy as heck!
                          Old World Stone & Garden

                          Current WFO build - Dry Stone Base & Gothic Vault

                          When we build, let us think that we build for ever.
                          John Ruskin

                          Comment


                          • #14
                            Re: Castable - How thin can you go?

                            In the first place, pizza is not a food you make at a picnic or tailgate. Dough, cheese, assorted ingredients that need to be kept at controlled temps, plus the variety of implements (peel, cutter, make table at the minimum) make it impractical. Save the pizza for home and cook appropriate foods for the activity.

                            Comment


                            • #15
                              Re: Castable - How thin can you go?

                              Originally posted by stonecutter View Post
                              Again, masonry has its limits when you add motion to the equation. You need mass when you are building with masonry...it is not a "portable" material. Is there other options besides one that are superfluous..yeah. Use a green egg or something similar...lightweight metal shell (relative to masonry) with a thin refractory liner.

                              I have never seen a WFO with a flying buttress, that must have been one heck of an oven..with a huge open space underneath.
                              Thanks again stonecutter!

                              I have to confess, I have been away from home for too long! So I don't know what a green egg might be!

                              Last time home, I saw that proportion sizes had increased though! Big Gulp, super Big Gulp.. But the size didn't make it taste better.

                              And no--I haven't seen flying buttress ovens either, but there are some big builds out there... lots of wood to fire one of those things up!

                              Old "Lone Ranger" and "Tonto" discussion--"Tonto says--you white man build big fire and stand far away, us ind jun make small fire and sit close!" both same warm! And no ethnic or racist slurrs intended! Just a different way of looking at things.
                              Economies of proper sizing!

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