Includes 3 vacuum cups and 20′ of ¼” I.D. vacuum tubing.
885-34 Vacuum Cups & Tubing, 1 pkg
How to Use Vacuum Cups & Tubing in Vacuum Bagging Operations
Once the vacuum bag is completely sealed to the mold, use a felt pen to mark the position(s) for the vacuum cup(s). Cut a ½” “X” in the vacuum bag film to provide a port through the bag for the vacuum cup. Where to place suction cup depends on the geometry of the part you are vacuum bagging. Typically, you don’t want to put it on what will become the finished part, but off to the side.
Cut tubing to the appropriate length, to connect the vacuum cups to the generator and make a resin trap.
We put vacuum sealant tape on the suction cup so it will stay sealed if vacuum is lost for a short time. Learn more by watching the video above.
Basic Vacuum Bagging
Vacuum bagging is a clamping technique that uses atmospheric pressure to press epoxy coated or saturated laminate together until it has cured. In the typical hull repair layup shown in the diagrams, the vacuum “bag” film is one half of an envelope. The hull (or mold if you are building a laminate) is the other side of the envelope.
When the envelope is first sealed, air pressure inside and outside of the envelope are equal (about 14.7 psi). When air is sucked from within the envelope, interior air pressure is reduced (to about 5 psi) while outside, atmospheric pressure remains the same. Everything within the envelope is compressed by the greater outside pressure pushing against the vacuum bag film and back of the hull/mold.
The greater the pressure difference between the inside and outside of the envelope, the greater the clamping pressure. In this case the pressure differential is about a 10 psi. The flexible contents of the envelope and bag conform to surface contour of the rigid hull/mold side of the envelope. When the epoxy cures, the repair laminate becomes a permanent part of the hull structure. In a molding operation, mold release applied to the smooth mold surface assures the cured laminate will not become a permanent part of the mold. When the Vacuum Generator is activated and air is removed from the envelope, the atmosphere presses Vacuum Bag Film upon the Breather Fabric beneath it. The breather presses upon the Release Fabric, which com- presses the repair laminate against the hull surface The excess epoxy is drawn through the Release Fabric into the breather material. The Breather Fabric resists total compression and therefore maintains an air space that allows air and excess epoxy to migrate from the edges of the layup to the port and out of the envelope. As long as the seal is maintained and the vacuum is held, the pressure of the atmosphere will keep the Vacuum Bag Film and everything beneath it packed tightly against the hull or mold. This clamping pressure must be maintained until the epoxy cures.—Excerpted from 885 Vacuum Bagging Kit Instructions
To learn more about vacuum bagging, read Rachael Geerts’s article Vacuum Bagging Basics at Epoxyworks.com