I've been mucking around with vacuum in my workshop ever since I read the story in the GAL journal about Charles Fox's vacuum setup.
I got a pump locally and got a kit from Joewoodworker web site that gives you all the stuff to build a cycling system like a compressor so it does not run continuously. Check out the web site for details. They have comprehensive plans.
I housed it in a mobile box with power outlets for tools. I used 2 empty propane tanks for the primary and buffer storage tanks but the web site has lots of different ideas including using pvc pipe. Its pretty cool.
This hooks up to what ever attachments you want.
Here is my holding jig. The large disk holds the back for working on the sides. This is very powerful grip. You would break the guitar before you ripped it off so long as the vacuum seal is good.
Taps let you back off the pressure and turn the guitar before the vacuum fully lets go to get to a different section. It works very smoothly.
And the small disks are flexible and will conform to the shape of either the top or the back.
And I have an LMI bridge clamp jig. Here it is with a pencil to show you how it conforms and places even pressure on every sq mm.
To make the large and small disk I first made a ply positive form in my 15 ft radius dish. I covered that with sand paper and used that to make a smaller copy of the 15 ft dish. You need to match it your back radius because it will distort your back if it is a different radius. The large one is covered in cork with closed cell foam in a small groove around the edge and routed grooves so the vacuum can get out to the edge so the whole surface is working.
The small disks are white chopping board plastic also with closed cell foam also in grooves. The grooves give the foam somewhere to retreat to under compression without totally crushing. Check out Charles' article if you can.
The next thing I need to do is make a press for the top and back braces. The benefits are that you can totally pre carve your braces and the clamping pressure is even on every part of the brace, even very thin feathered down ends. As Mr Fox says, it avoids hot spots from go-bars.
I have some rubber sheet from LIM. I'll let you know how it goes.
Cheers
Dom
