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  • Dome insulation Help needed

    Need help here... How much perlite will I need for a 4 inch layer of insulation over my 42 inch oven dome. My math says around 2,2 cubic meters and that seems a bit too much?
    My build: http://www.fornobravo.com/forum/f8/4...way-19491.html

  • #2
    Re: Dome insulation Help needed

    42" inside diameter + 4.5" brick thickness = 46.5" diameter to inside of insulation = 23.25" radius to inside of insulation +4" insulation = 27.25" radius to outside of insulation...

    (23.25)^3 * 3.14159 / 2 = 19,741 cu in oven volume
    (27.25)^3 * 3.14159 / 2 = 31,784 cu in volume to outside of insulation

    Difference is 12,043 cu in / 1728 (# cu in in cu ft) = 6.97 cu ft

    That should equal about 0.2 cu meters.

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    • #3
      Re: Dome insulation Help needed

      Steellearning:

      I did the math this way:
      You have to subtract the volume of the dome without insulation from the volume of the insulated dome.
      I would suppose that 42 is the inner diameter, and the brick thickness is 4 inch. Thus:
      The UNINSULATED dome diameter is 42+4+4 = 50, r for uninsulated is: ru = 50/2 =25" = 0.635 m
      The insulated dome diameter is 50+4+4 = 58 (4" insulation is considered), r for insulated ri = 58/2 = 29" = 0.737 m


      Subtracting the volumes (We divide by 2 because domes are hemispheres):
      [3.14*4/3*(ri^3-ru^3)] / 2 = 0.3 cubic meters of perlite required.

      Please recheck my math for any mistakes.
      Why is this thus? What is the reason for this thusness?
      I forgot who said that.

      Comment


      • #4
        Re: Dome insulation Help needed

        I did not check the math, but don't forget David's theory of 15% reduction in volume for V or P crete. I came up short on my floor insulation. So I did not make that mistake with my dome .
        joe watson

        "A year from now, you will wish that you had started today "

        My Build
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        • #5
          Re: Dome insulation Help needed

          Originally posted by Gulf View Post
          I did not check the math, but don't forget David's theory of 15% reduction in volume for V or P crete. I came up short on my floor insulation. So I did not make that mistake with my dome .
          Gulf,

          You mean the insulation volume should be 15% the dome volume?
          Why is this thus? What is the reason for this thusness?
          I forgot who said that.

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          • #6
            Re: Dome insulation Help needed

            Originally posted by v12spirit View Post
            Gulf,

            You mean the insulation volume should be 15% the dome volume?
            No. I mean the dry volume of vermiculite and cement is reduced by about 15% once you add water and mix it, creating a wet workable mix.
            Kindled with zeal and fired with passion.

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            • #7
              Re: Dome insulation Help needed

              Originally posted by v12spirit View Post
              Steellearning:

              I did the math this way:
              You have to subtract the volume of the dome without insulation from the volume of the insulated dome.
              I would suppose that 42 is the inner diameter, and the brick thickness is 4 inch. Thus:
              The UNINSULATED dome diameter is 42+4+4 = 50, r for uninsulated is: ru = 50/2 =25" = 0.635 m
              The insulated dome diameter is 50+4+4 = 58 (4" insulation is considered), r for insulated ri = 58/2 = 29" = 0.737 m


              Subtracting the volumes (We divide by 2 because domes are hemispheres):
              [3.14*4/3*(ri^3-ru^3)] / 2 = 0.3 cubic meters of perlite required.

              Please recheck my math for any mistakes.
              Thanks v12spirit
              Looks like 2 x 200 ltr. bags of perlite will do the job.
              My build: http://www.fornobravo.com/forum/f8/4...way-19491.html

              Comment

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