On 6/29/97 9:28 PM, Rick Mainhart at email@example.com wrote:
>Ah ... a cubic yard is 3 x 3 x 3 or 27 cubic feet.
>27*.67= 18.09 cubic feet required (using your figure)
>18.09/3.14=5.76 feet depth required for 1 foot diameter;
>18.09/6.28=2.88 feet depth required for 2 foot diameter.
Hmm. My back of the envelope computation says something isn't right. If
you double the diameter, that quadruples the volume per foot of height.
If 5.76 feet is right for a 1 foot hole, then a two foot hole should
require 1/4 of that, or roughly 1.5 feet, less about an inch or so.
The volume should be 2*pi*h*r**2. For a 1 foot diameter hole, that's pi/2
cubic feet per foot of height, or around 1.6 cubic feet per foot. Such a
hole would have to be over 11 feet deep to be 18 cubic feet.
For the 2 foot diameter hole, your computation is correct, as each foot
of height yeilds 2pi cubic feet.
>Not sure whether I'd try to second guess the engineering.
Certainly not with math like that. <grin>
Bill Coleman, AA4LR, PP-ASEL Mail: firstname.lastname@example.org
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