Choosing Equipment for Vacuum Bagging

A simple blower won't do the job, but the right gear is easy to find.

I have a 2 hp blower that will generate 62" of suction in water, which by my calculation is about 4.5 Hg. Is anyone using a blower to produce vacuum? Are you producing enough vacuum for template clamping, veneer bagging, etc.? Are you satisfied with your setup? I sure would appreciate a "been there, done that" story.

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
You are comparing a Mack truck to a Mini Cooper. For vacuum bagging/clamping, you need a vacuum pump/compressor. These are typically 1/4hp-3/4hp. The outputs are measured in CFM (3 typ) and potential vacuum in inches of mercury (29 typ).

Gast has a firm grip on the industry and makes beautiful little pumps. There are two basic types: rotary vane and diaphragm. The rotary has an electric motor that spins a carbonfiber blade to create the suction. The diaphragm pumps are nice because they are designed to run continuously. With rotary, you typically have to rig up gauges and pressure switch, etc. to tell the sucker to start and stop. The only thing a big vacuum pump does is pull more cfm, like a vacuum cleaner. All most woodworkers need is a nice little 1/3 - 1/2 hp Gast diaphragm pump. These retail for $300-400. Look on the surplus/discount sites and you can usually pick up a hundred or so for $100. Try Surplus Center and look for Gast.

From the original questioner:
Thanks... just as I suspected. While the regenerative blowers are promoted within industry as vacuum sources, I guess the fine print says high cfm but low Hg. So what can I use these blowers for?

I purchased a venturi vacuum from E-bay that will produce 28Hg and have pressure switches and the valves as well as some large diameter PVC that we'll use for a holding tank.

From contributor A:

If you can afford the $100 for a diaphragm pump, I would forgo the venturi. They are basically a poor man's method of making a temporary vacuum. The problem is that your air compressor is providing the oomph, and hence may be cycling or running a lot. It also tends to tie up the compressor. I just have a light switch on my little Gast and turn it on and come back the next morning. You can sleep very well at night with these little units. The other trick if you are bagging a large object (ie 40' sailboat) is to use your shop vac to suck 99% of the air out real fast and then let the vacpump bury the remainder. As for your 2 hp blower, it sounds like it is somewhere between a dust collector blower (high CFM) and a vac pump (highest static pressure). Maybe you can use it pump out your shop when it floods.

From the original questioner:
Thanks again for your input. I have ordered the venturi. We have a moderate (7hp) compressor and I plan on a vac storage tank. Initially using for jig holding, etc… no bagging yet.