#1  
Old 06-23-2014, 06:25 AM
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Default 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?
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Old 06-23-2014, 08:18 AM
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Default 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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Old 06-23-2014, 09:46 AM
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Default 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.
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Old 06-23-2014, 04:38 PM
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Default 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 .
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Old 06-23-2014, 07:35 PM
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Default Re: Dome insulation Help needed

Quote:
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?
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Old 06-23-2014, 08:31 PM
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Default Re: Dome insulation Help needed

Quote:
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.
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Old 06-23-2014, 09:09 PM
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Join Date: Aug 2012
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Default Re: Dome insulation Help needed

Quote:
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.
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