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re: vacuum lift and the jewelry principle
24 jan 2000
brian a. m. stuckless mentions skyballs...
what's the minimum size, if a square foot of 4-year us r0.8 greenhouse poly
film with 90% solar transmittance weighs 0.02 pounds, and it can support
15 psf on 4' centers, and the internal struts are made from 4" pvc pipe
weighing 0.6 pounds per foot, and the ball floats near phila in january,
when the average outdoor temp is 30.4 f and the average daily high is 37.9
and the average humidity ratio is 0.0025 #h20/#dryair and 620, 1000, 430,
420, and 190 btu/ft^2-day of sun falls on a horizontal surface and south,
west, east and north walls?
the ball might be held up by a mixture of warm air and water vapor during
the day, and a partial vacuum at night and on cloudy days...
nick
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