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Nightmare vcrete insulation layer

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  • Nightmare vcrete insulation layer

    Today I put on my 3 inch of ceramic cloth and then started to put on the vcrete. I used a 6 1 mix of perlite and cement.

    It was a nightmare to try and get it to stick. I was not able to trowel it on and ended up just hand slapping it in position. Almost as much fell off than stayed on. (I guess if you throw enough mud at the wall some will stick!)
    The cloth moved and kept breaking the vcrete which would fall off. I tried with numerous different "wetness" of mixture. Too dry fell off wouldn’t even bind together. Too wet would just fall off. Got it right towards the end and it would palm on and spread a little but too much pressure would lead to the fabric being pushed in and the the vcrete falling off.

    Anyway got it finished.

    But .....am I being too much of a perfectionist as it is cracking already. Should I put another thin layer on once it has set to cover the cracks?

    I am leaning towards I will be ok as I have 3 inch of blanket underneath and will be putting stucco on the outside.

    I only really put the vcrete on for extra insulation and for a better surface for the stucco to bind too.

    What do you all think.??
    Willl these cracks be ok?.
    Haven’t even started curing yet. These happened as it was air drying while I was still finishing the layer.

    Click image for larger version

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  • #2
    It’s difficult for me to keep up with your build. Its best to start a single build thread in the beginning so folks can follow and offer advice as you go.
    Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build

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    • #3
      (Disclaimer: I just built 1 oven, so not really more experienced than you)

      did you use chicken wire to firmly hold the blanket in place? Seems like the blanket moved under the weight of the vcrete.

      It is not ideal. As it will not provide a stable support for your stucco. Vcrete is not so strong, a thin layer will just crack in the same places.

      If you need a weatherproof dome, then I would either redo the vcrete (this time using a curved tool as a movable mold, holding the vcrete in place while that you can compress it somewhat). Or fix the cracks with a crack filler (fit for outdoor use).

      Then make sure to use some kind of mesh in your stucco to give it tensile strength.

      if this was the point where planned to start curing, you might as well do it with it cracks in place, so that steam can easily escape and all the cracks can settle before you fix them.

      I had some vcrete cracks after curing (less severe then yours). Used a filler. So far holding up.

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      • #4
        I just finished the vcrete on my dome too, and the top is definitely weaker/crack-ier than the bottom. It's at least 2 inches thick. I did not use chicken wire.

        I'm not going to worry about it and just move to the stucco layer. I do like the idea of using some crack filler. I can't imagine re-doing the whole thing, because I think it would have the same end result.

        might put some chicken wire or mesh down overtop the vcrete for some more strength and support.
        My 36" build -&- Youtube Timelapse

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        • #5
          No I didnt use chicken wire and yes it cracked because of the blanket moving. I will put chicken wire over the top of this and do the stucco. I have started curing as I though the same thing and the heat doesnt get thorught to the vcrete anyway because of the blanket. So I assume the curing is for the thermal brick and floor only. Im on day 3 of curing now and no more cracks inside or in the vcrete. Chicken wire and stucco it is.

          When curing where do you shoot the laser thermometer as I get very different temperatures on the floor sides and roof......The floor is colder than the sides and the ceiling is hotter. I have been using the side walls as the guide for the temperature. Here is what I have done so far based on the side walls.

          12 hrs at 300 - 350 (first 6 at 300 or below)
          12 hrs at 350-400.
          Tommorow will be 12 hrs at 400-500.

          On a side note: Whilst curing I am getting lots of smoke out the front. The chimney doesnt seem to draw much. I have exteded it but same result. Chimney is now 4 1/2 ft tall. But still smoke out the front. Is this because the fire is not that hot at the moment or have I messed up in the build some how.

          I do have a large vent a I manufactured it out of mild steel. 9inch x 23 inch by about 12 inch tall. Is this too big and Im losing draw because of it?

          P.S Guf is there anyway I can join my threads together or should I just copy past them all into 1?

          UPDATE: So the smoke thing I think the vent is too small. Or the oven door id too large. I have placed 2 bricks either sideof the oven entrance to reduce it from 16 inch wide to approx 8 inch wide and the smoke goes right up the vent no problem. Im hoping that when the fire is at full temp there wont be as much smoke and the entrance to the dome is not too small. Otherwise it will have to be making a bigger vent. Probably go from 9 inch wide to 12 inch wide. will have to wait and see...Fingers crossed. (or just place bricks in the entrance when first firing!)
          Last edited by TommyTongue; 08-19-2020, 08:59 PM.

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