john12ax7 said:
How much did they charge to CNC the 4x8 sheet? Was thinking of going that route.
I don't recall exactly. It was maybe $250 USD. The sheet was ~$70 USD maybe. So $300+ total. I sent out an email to ~5 companies at the same time (same email but separate so that they would not know it was a "bakeoff"). I just used the first guy who replied but after about a week I got lower bids (one was like $100 USD I think).
However beware. I did this twice, used two different guys and both times they screwed up pretty significantly. The first guy completely lost a piece (and not even a small one - it was like a 1'x3' piece). Fortunately it was the removable back of the Supro head cab so I was able to build the project and then added the missing piece to the second run. But the second guy was actually worse. He incorrectly cut one of the pieces and several of the boards were a little warped. It also took about 3 months for reasons that were never clearly explained.
Unfortunately here in NJ USA this sort of thing is considered a "left-footed" job so I could not really complain. When I went to pick up the second job I saw immediately the long sides were warped but I didn't even bother to say anything and just paid the guy and left. My guess is he bought the sheet and then put it somewhere were it dried out and warped.
Fortunately the design had numerous places where multiple pieces intersected at right angles (meaning it was designed to be glued together) so it all straightened out in the end. And it helped that I mounted the steel rails (from Redco) before gluing it all together.
Because the CNC cutting is so accurate, an alternative construction method might be to make tabs that fit together exactly. Like a jigsaw puzzle. With the right screws (small hex heads maybe), such a design could be very strong (possibly even without glue).
If you go the woodworking glue route, I used a 50/50 mix of water/glue to pre-moisten all joining surfaces and then used ample amounts of 100% glue on both surfaces just before clamping it all together. That allowed the glue to really get deep into the birch ply. Then, after it was mostly dry on the surface, I did another pass of glue into all corners and smoothed with my finger. This is surprisingly strong. Probably because the CNC is so accurate, the joint surfaces are tight. Although I do not know if it would survive water.
If I were to do this again (and I probably will since I'm already running out of rack space), I would probably try to buy the sheet of Birch ply myself so that I would get a very high quality, straight piece. The more layers the better. Anything with less than 5-8 layers is not good. And it should be possible to find one side plug-free so that you can apply a finish if desired (although this would require the pieces to be layed out on the sheet in a just such a way). That would also give me an opporunity to meet the guy, shake his hand and be very interested in what he was doing. The end result will almost certainly be better.