BTW: When I did my hull I had a well sealed bag. As I recall, the
generator ran about every 15 minutes and my 30gal compressor ran about every
50 minutes. Depending on how well your bag is sealed, your mileage may
vary. I used construction adhesive for my bag sealant.

"Dave Schneider" wrote in message
...
I did all my vacuum bagging of hull and rudders using a 2 stage Gast vacuum
generator. I have no idea how to build one. I originally thought it was
a cheap way to have a vacuum pump. By the time I assembled the whole
contraption, "I could have had a V8".

Here's a pic:
http://groups.msn.com/UH13p/toolsoft...oto&PhotoID=49

To minimize cycling of your compressor, you really need to incorporate a
vacuum reservoir which means you need a tank, hi-flow check valve, gauge,
vacuum switch, and solenoid valve. Basically the way it works is that
you create vacuum in a tank and when you get to the desired vacuum, the
solenoid valve shuts off the line to the air compressor. The check valve
is so you don't loose the vacuum. As your vacuum bag inevitably leaks,
the volume of the tank is enough to compensate and keep the vacuum.
Eventually the vacuum drops below a specified level and then the vacuum
air hose kicks in again. With the exception of when the air compressor
runs, and when the vacuum generator runs, the system is completely silent.
That makes it real easy to find leaks.

If I were to do it again ... I'd probably get a vane vacuum pump with good
volume. Check out eBay.




"Tom" wrote in message
oups.com...
Pretty sure Nick Muller already did this and has the dimensions on
his web site...maybe Don Foreman will post link....

Thanks, found it...
http://www.metalworking.com/DropBox/
http://www.metalworking.com/DropBox/...ri_sketch2.jpg
http://www.metalworking.com/DropBox/venturi.txt

I just wanted something quick and cheap, but I'll look into
the fridge compressor if I get my hands on one.

Thanks,
Tom.
http://www.TomEberhard.com