The Venturi Vacuum Generator includes a silencer. Generator develops over 20 inches Hg (mercury) of vacuum (10 psi) at .4 SCFM (standard cubic feet per minute) and is designed t run off of conventional shop air compressors delivering at least 65 psi at 3/5 SCFM continuously.
885-6 Venturi Vacuum Generator, 1 ea.
Venture Vacuum Generator
The air-operated Venture Vacuum Generator is a simple, low-cost device that generate a vacuum using air pressure supplied by a standard air compressor. Its portability, relatively low cost and the accessibility of compressors in many shops and homes make the Venturi Generator ideal for smaller vacuum bagging projects.
Whichever vacuum generator you choose, it must hold a continuous vacuum until the epoxy reaches an effective cure. This may take 8 to 24 hours depending on the hardener selected and ambient temperature. After all the materials are in place, turn on the vacuum source and allow vacuum to be continually pulled until the epoxy has cured.
Tips to make vacuum bagging easier
When repairing long or laminating larger areas, use an extra layer or strip of breather fabric to insure the complete removal of air from the bag and an even distribution of pressure on the laminate.
When making ½” “X” cuts in the bag film, circle them with a felt marker so you can locate them more easily.
To avoid making an impression in the surface of the repair place the Vacuum Cups on a part of the film not directly over the wet laminates.
Use a tank type vacuum cleaner or shop vac to evacuate a large or bulky bag setup before applying vacuum from the Venturi Generator.
Make a test layup to determine the exact number and weights of laminate cloths needed to match the specific thickness required for a repair. Using a flat smooth surface like a layer of glass, lay up a progressively thicker series of the kinds and weights of laminates that you like to use and apply vacuum pressure. When cured, measure and record the thickness for each combination.
Small leaks in the bag, seal or mold will have a cumulative effect of reducing vacuum levels under the bag. Seal all leaks with sealant or tape to improve vacuum levels. Some materials such as press board are porous enough to not be suitable as a mold surface unless they are coated and sealed with epoxy.
A word of caution
The vacuum equipment and methods described in these instructions should not be used with adhesives that contain solvents or catalysts having medium to high vapor pressures. A very narrow band of latitude in time, temperature and pressure is available when applying vacuum to such adhesives and missing any mark can cause unreliable repairs or outright failure. A good rule of
thumb is, if some part of the product evaporates as a part of the curing process, it has a fairly high vapor pressure and should be avoided. Unsolvented epoxies in general and WEST SYSTEM epoxy in particular, have low vapor pressures and are very suitable for vacuum application.
Read more about vacuum bagging in Rachael Geerts’s Vacuum Bagging Basics at Epoxyworks.com.