For smaller stuff, you meant that you use form (male and female) and clamp ?
Yes, or sometimes just an inner form, and bend over it with cauls and clamps. For instance, arches. Anything not so wide that conventional clamp pressure (without complicated cauls) will cover easily.
As for the discharge hose, it is used as a pressure vessel ?
it is used for a complex part or slight 3D shape with broad surfaces, where conventional clamps won't reach, and Vac-bagging would get unwieldy due to perhaps length, say. Or where the pressure hose is either more convenient, or can apply more pressure than would result from Vacuum.
The pressure hose has to be resisted on one side by the form, & on the opposite side by clamps, cauls, or permanent structure such as I-beams.
I love the capabilities vac-bagging offers. But it is a high nuisance set up for many parts. The form and the layers can't have sharp projections (puncture) and there are limits to how well you can align parts especially with curve reversals ("S-curve, e.g.) while putting them in a bag. This might be quickly obvious when you think about bending a pile of laminae into an arch. If it is a low, flat, wide bow, vac bag is great. And very easy to lay up and bag. If it is narrow (say 6" - 8" wide) and bent into a relatively small diameter (say 3' radius/6' diameter) over more than 30° or 45° of arc; or a full hairpin. it becomes very difficult to manipulate the large, stiff pile of material, and even to get it in a bag in such a way as to effectively press it.
When you start drawing a vacuum, the bag wants to go where there is least resistance. For example, initially it will go _under_ anything not already pulled well down or laying comfortably on a gentle form. If the lay-up is such that you can't physically restrain it to the form to keep the bag where you want it until the vac pressure is enough to take over and hold it, the bag can get in the way enough to either mess the shape up, or tear.
For largish lay-ups there is also the nuisance & cost of the peel-ply layer and the bleeder layer all laid out smoothly under the actual membrane.
A lot of people use vacuum pressing for veneering flat work & it is excellent for that; especially with a clamshell press designed for the app. If you have to make a flat platen (to be sure the work stays flat) and bag it all, it gets complex again.
It's really a fascinating field of woodworking.
Amen!
If another post was started, I could post pics of examples.
Do not want to hijack the post of your beautiful table work.
smt
