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?
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Dome insulation Help needed
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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.

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^3ru^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.
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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 Album / My Build
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Re: Dome insulation Help needed
Originally posted by Gulf View PostI 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 .
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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Re: Dome insulation Help needed
Originally posted by v12spirit View PostGulf,
You mean the insulation volume should be 15% the dome volume?Kindled with zeal and fired with passion.
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Re: Dome insulation Help needed
Originally posted by v12spirit View PostSteellearning:
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^3ru^3)] / 2 = 0.3 cubic meters of perlite required.
Please recheck my math for any mistakes.
Looks like 2 x 200 ltr. bags of perlite will do the job.
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