Conventional clamps work well on th

Conventional clamps work well on thicker materials and narrow laminates like beams and
frames. Large projects may require a large stockpile of clamps. Staples are commonly used
to clamp thinner wooden plies when laminating wide panels for bulkheads or for applying
veneers to cold-molded hulls. Vacuum bagging offers many advantages over conventional
clamping or stapling techniques. As with other laminating methods, different materials can
be incorporated into the laminate. Materials can be selected specifically to match the structural
requirements of the component rather than the limitations of the clamping method.
Even clamping pressure
Mechanical clamping or stapling applies pressure only to concentrated areas and can damage
fragile core materials in one area while not providing enough pressure for a good bond
in another. When placed in a closely spaced pattern, staples exert less than 5 psi of clamping
force and then only in the immediate area of the staple. They cannot be used at all if you are
laminating to a foam or honeycomb core because of the core’s lack of holding power. In addition,
extra adhesive is often required to bridge gaps that result from the uneven pressure
of clamps and staples.
Vacuum bagging, on the other hand, delivers firm, evenly distributed pressure over the entire
surface regardless of the type or quantity of material being laminated. This allows a
wider range and combination of materials as well as a superior bond between the materials.
Vacuum bagging’s uniform clamping pressure across the laminate results in thinner, more
consistent glue lines and fewer voids. Because atmospheric pressure is continuous, it evenly
presses on the joint as the adhesive spreads evenly within.
Control of resin content
Vacuum bagging also gives you the means to control excess adhesive in the laminate, resulting
in higher fiber-to-resin ratios. This translates into higher strength-to-weight ratios and
cost advantages for the builder. See 4.2.2.
Custom shapes
Another big advantage of vacuum bagging is in the simplicity and variety of the molds used.
Keep in mind that the atmosphere is not only pushing down on the top of the envelope, but
it is also pushing up equally on the bottom of the envelope or mold. Since atmospheric pressure
provides equal and even clamping pressure to the back of the mold, the mold only has
to be strong enough to hold the laminate in its desired shape until the epoxy has cured.
Therefore, most molds can be relatively light weight and easy to build.
Efficient laminating
Because all of the materials in the laminate are wet out and laid up at the same time, vacuum
bagging allows you to complete the laminating process in one efficient operation.