From
James Bodnar's Combat Page (A vacuum system for RC planes/gliders)
Used with permission.
Continuous
run vacuum pump for vacuum bagging.
Here's
what it is... It is the pump out of a small refrigerator. We had a fridge
that didn't have any freon in it so we disassembled it. The best place
to find a pump is at a appliance repair or appliance second hand shop.
If you get the whole fridge, please recycle the freon, don't just cut
the lines. I don't want to get skin cancer because you depleted the
ozone. Let me explain how this contraption works. It creates pressure
on one side and a vacuum at the other. On the left it the vacuum side.
We bought a brass fitting with a 1/4 compression ring on one side and
male 1/8 pipe threads on the other. It screws into a T-coupler. One
side goes to the fuel pump/vacuum gauge, the other goes towards the
vacuum bag itself. But, before it gets to the bag, we need a way to
regulate the pressure. Without it, the pump would draw max vacuum (around
27 inches of Mercury I think) and would crush the foam in the vacuum
bag.
My Dad
found the perfect thing. It is a brass valve designed to bleed air out
of natural gas lines for natural gas fireplaces. From there, it goes
to clear 3/8 tubing to the vacuum bag. On the right side of the pump
is the pressure side. The pump has oil in it. As it operates, a little
of the oil flows out the pressure side. To fix this, that white bottle
on the top of the pressure line is a reservoir. The bottom of the bottle
(pointing upward in the picture) has holes drilled in it to let the
air out. As the air and oil come out the tube into that bottle, the
air slows down, the oil separates from the air and stays in the bottle
as the air escapes out the bottom of the bottle. When you shut the pump
off, the oil runs back into the pump. We've run this pump for as long
as 48 straight hours with no problems. It did get slightly warm so we
put a household fan on low pointed at it. The pump works great and is
so quiet, you hardly know it's running.
Now, you
may ask, what am I vacuum bagging? My combat wings of course. I found
a great place for inexpensive Fiberglass, Kevlar and Carbon Fiber fabric,
West system epoxy, and peel ply. It is called the John R. Sweet Co.
It is a nice sized business that got its start from supplying canoe
and kayak enthusiast with composite materials. He now caters to Model
enthusiasts too but at a signifigant savings compared to those other
places. I'm using a two inch wide piece of 5.7 ounce Carbon Fiber on
top and bottom of the thickest part of the wing, a layer of 1.7 ounce
Kevlar from there forward then a piece of 2 ounce fiberglass over the
top and bottom of the wing. Put on your epoxy, squeegee it off and put
it in the bag for two days. Voila.

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