On Tue, 09 May 2006 19:51:15 GMT, Pat Barber wrote:
The electric one looks OK, and its a good price. A couple of things I think
you give up, relative to the costlier systems, are (1) the pump runs
continuously, and that noise might be a concern; (2) it is a small pump, and
it will take a long time to pump down a large bag & fixture.
I wouldn't take the hand-operatoed version seriously for anything other than
simple veneering of small work using PVA glue. Aside from the obvious
difficulty pumping down a larger bag & fixture, the fact is that no system is
entirely leak-free, so an application using a slow setting adhesive would mean
you have to periodically pump down the bag.
I built my system using parts purchased from joewoodworker.com, and have a
system with decent capacity (a 4x8 bag and large bending form is no problem)
using a regulated pump for about the cost of the pump & bag from Woodcraft.
The OP didn't say what his application is, but he did say that he didn't want
I have to disagree with this, at least related to some vacuum bags. My SO has
that vacuum storage system you see on the Home Shopping network.
She has a couple that have stayed fully 'vacuum packed' for over two years.
Some leak some don't.
The pressure developed by the vacuum bag is the result of creating a
pressure differential between the inside and outside of the bag.
The pressure outside the bag is ~14.7 lb/in^2 (psi) at standard
temperature at sea level. The absolute maximum pressure the bag can
develop is 14.7 psi regardless of how good the vacuum is inside the
bag. Sucking harder can't make it better.
So if you have a partial vacuum that leaves a residual pressure inside
the bag of 0.1 psi is this really a big deal? Is the veneer going to
lay flatter with an additional 0.1 psi?
And is it really that much easier to keep the bag sealed against a
differential of 14.6 psi than it is 14.65 psi?
On Tue, 09 May 2006 15:00:49 -0700, Wes Stewart wrote:
Perhaps you misunderstood. My point is that the common storage bags, emptied
by a household vacuum cleaner, do not achieve the level of vacuum as is
employed in a veneer press (by at least a factor of 2 or 3), and at the lower
inside/outside differential, it is easier to maintain that partial vacuum.
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