You're not going to like my answer. Here's a glue-up that was only 10 inches wide by 16 inches long, and I still didn't have enough force/pressure to do it properly. As I turned this on the lathe, I found I still had a visible glue line closer to the center in one area.
When you do the math, you see how difficult the problem can be with a face-to-face glue-up. The amount of force that you need is equal to the desired pressure times the surface area of the joint. So in your case, it would be 72 inches times 24 inches (1728 square inches) times 14 psi = 24,192 pounds of force. And that's only for atmospheric pressure. Normally, I recommend 100psi clamping pressure, which would result in 172,800 pounds of force.
To the contrary Rick, I
do like your answer. You make a good point and I am not sure that water bottles is going to get a consistent glue squeeze out across the length of every board in the stack. If I am to cut these into 2x4's and 2x6's, then I need 100% (not even 99%) glue coverage and bonding. I don't want one of my laminant 2x4's to separate later.
If this run is successful, I plan to repeat this going forward because it is the only way I can afford 2x4's and 2x6's with the lumber prices here. Two of the 2m x 60cm x 1.8cm sheets is ~ 13.50 Euros, so 26 Euros for the pair. I can cut these into 6 boards that are close in dimensions to a 2x4. The price for me would drop from Euro 14.25 to 4.33 (26 Euros / 6 boards).
Looking at your photo and the price of pipe clamps here, your rig would cost me (not including pipes) about 600 Euros (USD $702). While your rig sure looks stout, it isn't quite in my budget this month :wink:
I could run (underneath) a row of perpendicular 4x4's with another row on top, the two tied together a 10cm (.40") bolt (threaded rod), some washers, and wing-nuts.
I made a rough sketch of my clamp idea:
I can buy a garden 4x4" (9x9cm, 2.4 meters long for EUR 13.50) and get 3 per board. I would need 2 pieces for each "clamp" for a wood cost of 9 Euros and hardware of about 2 Euros (1 meter long 10mm threaded rod is .95). So, about 11 Euros per clamp. If spaced 12" apart, I would need about 6 of these (66 Euros), if spaced every 8" then 10 of them (110 Euros). Certainly beats 600+ Euros and I think would get the job done.
I appreciate everyone's input - thanks to all.