In article ,
Doug Miller wrote:
In article 1109979204.fad47d4df84da263be0314fbc737ff5f@teran ews, "Joe
Wilding" wrote:
vacuum bagin works very well in this application. you get very uniform
clamping pressure with a vacuum bag, and do not need extra boards to
distribute the load, like with clamps. Like the other poster said, just make
sure you have it supported flat when you glue it up. Assuming you get 10
inches of mecury vacuum pressure (which is real easy to do near sea level,
even with an old worn out vacuum pump), you will be applying over 12,000 lb
total force to your glueup. It is hard to match that with weight.

Not sure your math is quite right here... It's a lot of force, I grant you,
but I don't think it's quite that much. Here's how I figure it:

10" mercury = approx 1/3 atmosphere = approx 5 lb / sq inch.
13"x96" = 1248 sq in.
5 psi * 1248 sq in = approx 6250 lb.

Depends on how one is measuring -- a 10" reduction "below normal pressure",
or a reduction *to* 10" of pressure.

If it's a reduction _to_ 10" (a circa 20" 'differential' to the outside world),
then the 12,000+ pounds is right. 1296*14.7*(29.92-10)/29.92 = 12,683+ grin