I built my vacuum bag press from scratch last year and I was itching to try it out. A project came along that was just perfect for it. Curved plywood.
The pump is a pneumatic venturi that I got from joewoodworker dot com. It was the most expensive part of the build but not that expensive. It was surprisingly efficient at drawing a vacuum.
As you can see, in an Arizona summer it drew 24.5 inches of Mercury.
Subsequent builds I acheived 27 to 28 inches of mercury, which is pretty good, if you’re taking notes.
Eventually I will put an automatic valve on it, but I found if I hang out in the area a couple hours while it is in the press and take note of the pressure guage I can manually recharge every few minutes and not have an issue.
For the bags, I found I can buy the same vinyl in rolls at the fabric store (10mill thick instead of 30mil of the commercial ones) and buy heavy duty double sided tape at HD and make “semi-disposable” bags for real cheap. It worked out great. Besides, no one makes the 10 foot bag that I would need for this project.
The first step in the actual plywood making was to create my form. For this I made a type of torsion box from 4’X10 PB which I laminated with 3/8” wiggle wood. No additional layers were needed.
My daughters paid a visit just as I was gluing up for the top and they we eager to lend a hand.
Before running the full laminations, a test was in order. I needed to be sure this system worked before committing expensive plys and veneers to this. Besides, I need to create color samples too, so it fit the bill perfectly.
The layers from back to front looked like this; 20 mil Polybak Liner backing, 1/8” MDF, 3/8” 3-ply wiggle wood, 1/8” MDF, 20 mil Red Oak veneer face. If you look closely you can see the plys for the finished panels underneath the form biding thier time.
I used standard PVA adhesive for the plys and chose NOT to put the form in the bag. At this size, the bag would crush the form anyway, so I used the off-fall from the form ribs as cauls on top of the bag. It held its shape without any coersion at all. Nice.
At the time of this project, I was cramped into 1/2 of a 2 car garage. It always looked cluttered, but when this took most of the space, it got crazy for a few days.
This was to be part of a rostrum in a church, actually a Jewish Tempe. Someone attempted to do this themselves by bending 1/4” ply over a frame and failed. Too many bumps along the way, finishing issues and the like. Thicker plywood would make for a really clean and quality look and I got the nod to finish the job.
Unfortunately I don’t have pics of the layups in the press. I had my hands full spreading glue under a timer. Even with a helper this was an intense process. The panels are just over 9 feet long and there were a couple inner seams in the substrate. I staggered the seams throughout the layers and prejoined these whenever possible before the final layup.
Here is a look of the finished panels just before delivery.
The Finished Installation:
I think these speak for themselves.
Another satisfied client.
Thanks for following along.
-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251