vacuum bagging

Some web sites say a shop vac can pull 4" of Hg. 1" of Hg = about 70
lbs. per square foot, so using a shop vac would be like placing 280
lbs of weight on each sq. ft. Of course a full vacuum would be more
like a ton per sq. ft.

Found this link.
http://www.quigs.org/Farrier/bagging.html

Aslo, I think you can use a tankless air compressor as a vacuum pump with a
little work...