No reason that this wouldn't work except for practicality. You'll have to displace more water than you have air to remove for it to work. It's basic fluid dynamics.

The difficulty as I see it would be the volume of air to be removed relative to the amount of water you are able to "drop". i.e. once you've pulled all the vacuum that you can with the water, it may not be enough to remove the air from the carbon/resin and produce a vacuum of sufficient quantity if at all.

In order to pull 1 atmosphere of vacuum with water you need 33 feet. Not very practical.

In order to pull 1 atmosphere of vacuum with water you need 33 feet. Not very practical. Not sure I understand your description of the system, but as mentioned it must be closed.

I'm not buying any more gadgets to get used once, then gather dust for decades.

Besides, I'm obsessed with the question...

It isn't that I doubt you, but how do you know that? Would a 33' coil work?

I'm considering a very small volume and considering using Luer lock, standard I.V. equipment. In fact, I was thinking of an i.v. bag on a pole.

Well, on the surface, absolute vacuum will only generate atmospheric pressure on the item in the bag...which equates to about 14.5 psi. You can try to pull "more" vacuum on it but once you have removed all of the air, there is nothing else to pull. So, the vacuum bag can only match the differential pressure between the outside and the inside of the bag...i.e. 14.5psi atmospheric and 0psi inside the bag = 14.5psi total...and you can't generate less than 0 inside the bag because there's nothing left to draw out.

That said, you CAN increase the external pressure on the bag to increase the differential and the pressure on the item inside the bag. This is the principle of an autoclave. You first draw a vacuum on the bag, insert the bag into a pressure vessel, pump up the pressure inside the vessel and put a lot more pressure on the part. Hall Spars builds masts this way (and the Autoclaves normally employ heat as well).

You ~could~ also take your vacuum bag and lower it into water to create more differential in the pressure in the same way the autoclave works.

Straight out of Felder and Rousseau, "Elementary Principle of Chemical Process"

1atm = 33.9 ft H20 at 4 deg C.

Jake, I disagree. If the pressure (vacuum) gauge reads lower (less) than 0 psia then you are exerting more than 1 atm of pressure on the item in the bag. The benefit of the autoclave is that you can reach the high activation temperatures required for prepeg AND put it under pressure.

Ahh, but now I see that you just want to generate the vacuum with a column of water.

The coil won't work - you need 33.5 vertical feet in a column of water to match 14.5 psi. It's the only way to get the gravity to add up.

If you have a column of water descending 33 feet creating a vacuum space above it, then the water at the surface of that column will, in essence, boil. The vacuum space will have a considerable amount of water vapor in that volume. Will the presence of that "dampness" have an adverse effect on the curing process?