Just like autobody paint. Shooting fancy colors and clear isn’t all that hard. But if the bodywork, prep and environmental variables aren’t all in check, the job looks like shit.
I made a little vac system, and made a bunch of little parts and cosmetic stuff for bikes and cars. nothing structural yet. The mold has to be strong. I set the system to 18-22 inch’s of mercury worth of vacuum. Sofar so good, the fabric lays nice and tight to my mold/overlay without deforming it from too much pressure. Simply took a 8 gal air tank used to airbag trucks, used NPT fittings to plumb a hose to the project and the pump system. Got a little electric motor, belt and pulley over to a GAST vacuum pump with a check valve in the middle (can suck air out of the tank but the tank cant draw it through the pump when its not running). Put a vac. pressure switch in the mix to control it because i always have tiny pinhole leaks on my bag seals, so if the pressure drops a little the 8 gal tank acts like a capacitor. Then when the tank drops too far, the pump kicks on puts a few inches of vac back in and shuts off. I know its not good to have the project expanding/contracting a little like that but I made the system for like $75 and I am not building airplanes here so it works! Its fun and simple to play around with, give it a shot!