|Wide-spread myths notwithstanding,
vacuum-bagging is not rocket science. It is the simple expedient of removing
ambient air, so as to let atmospheric pressure aid in the
forming/laminating/drying/clamping of a work piece.
This removing of air can be accomplished with a
vacuum-pump, or a venturi vacuum-generator driven by a compressor (I built
two boats with one of those), or in a pinch, a vacuum-cleaner (this will
most likely burn out in short order, though, since a vacuum cleaner depends
on air flow to cool its motor).
The vacuum bag can consist of fancy vacuum film, or
any other plastic film, provided it does not have holes in it. The sealing
of said plastic can be achieved with official vacuum-bagging tape, or mastix,
or the doughy substance intended to paste posters to walls.
Whichever way you create the vacuum, you need a means
of adjusting it, so as not to crush your workpiece. This adjustment can come
from a valve, or some other controlled leak.
For myself, I would never vacuum-bag anything without
the benefit of a vacuum gage, lest I implode a board, or squeeze too much
resin from the reinforcements.
To achieve even pressure throughout the bagged area,
some non-collapsing substance needs to be introduced that prevents the
vacuum film from sealing itself against the bagged material. Breather fabric
is what the pros use, but a piece of string draped over the area will do
almost as good.
Lest this breathing device get glued to the bagged
material, some means of release needs to be added. The proper stuff is a
nylon-based fabric called peel ply. A Nylon taffeta from the fabric store
will do as well.
Let's put it all together!
A Surftech Tuflite just came in with a deep gouge in the