Very low teck but I have made quite a few foil wings with this and it seems ok.
A syringe with a spring inside adjustable with hose clamps.
the switch is just a spring loaded on, off push in=on out=off
When enough vacume is got the plunger pulls away from the switch and turns off the pump.
When vacume is lost or low the spring presess the plunger against the switch turning it on.
Easy to build, super cheap, a fairly high level of adjustability by sliding the caes of the syring either closer or farther away from switch.
The best idea I have found for vac sacking is to have an in line tank that also has vacume so when you open up at your part it sucks alot to start.
I once adjusted to high and the part was to dry, so I go for about half a bar now.
Just an idea.
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