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From: Earnest Bertram (spinmicro@compuserve.com)
Date: Tue 24 Nov 1998 - 15:30:31 GMT
Denis ;
Not sure what your comment meant but I have used a air compressor for my
vacuum pump for the last 8 years. I have built a total of 7 vacuum bagged
boats using this process. With a reasonable seal you can pull around 20
inch's of vacuum, more than enough for a vacuum bag. For many of the air
compressors the conversion is easy, just disconnect the interface between
the compressor and the tank. If you are lucky enough to have a pipe thread
inlet filter the suction side is easy. If you do not than you can do what
I did on my first conversion, where I cut a piece of plastic plate to fit
over the inlet hole and attached a pipe fitting to it. Because the
compressor is running in a suction mode there is little heat generated, and
vac seal can be used to seal the adapter to the compressor inlet.
To make the initial drawdown easier, connect a T fitting to the suction
tube, put a plastic 1 #189# " lawn valve on the fitting and connect your shop
vac to it. The shop vac will pull down around 2 lbs but at lots of volume,
good for that initial effort at sealing the bag. Once the bag is tight,
shut the valve and use the air compressor to draw the bag tight. The only
problem to be aware of is before you start make sure the oil level in the
air compressor is full as you will, if your compressor is as old as mine,
blow out a little oil. . Do not worry about the oil haze that seems to
fill the room. The problem is that the vapor pressure of motor oil is not
high enough to prevent it. In a real vacuum pump a special oil ( $30
/quart) is used. A $1 worth of motor oil seems a lot better Idea.
<p>Ernie Bertram
Head BOZO at BOZO boat works
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