I am looking for a way to clamp material to 4x8 sheets of plywood. The problem is trying to get even pressure across the sheets so it adheres evenly and doesn't bend during the dry times. I am planning to do up to 50 sheets at a time, finishing at 3/4". My current idea is to use ratchet straps over some angle iron or something similar to keep it flat. Any suggestions on equipment or ideas you may have would be helpful, thanks in advance.

Are you talking about gluing 4x8s to 4x8s or dimensional stock to the 4x8?

Ken
We will be gluing 3"x48" pieces to the plywood. Maple to maple plywood.

Will a vacuum bag worK?

If this is a money making venture and not just a one off then you will need to invest in an hydraulic press.
You will have significant adhesive and wood movement issues to overcome as well as working out how to accurately place 36 pieces of maple on each sheet and get it into the press without shifting.
What you are trying to do is similar to hardwood flooring. To manage wood movement, flooring is fixed on one edge and the other is free to move in the tongue and groove. Engineered flooring is essentially plywood and can be glued down with a flexible adhesive - flooring mastik. You might consider that technique.
Do not glue down solid wood to the ply and expect it to stay flat. Read up on wood movement from moisture cycling. I recommend "Understanding Wood" by Bruce Hoadley or just read through the numerous threads here on woodweb.
I strongly recommend making a sample and running it through simulated environmental cycles to test the feasibility of the product.
You do not want to end up with fifty epensive maple potato chips on your hands.

Tom
A press or something similar is what I am looking for recommendations on. Placement, glue, and wood are all things I understand well. What I don't know is what type of press or clamps are available for a project of this size

David
I had not considered a vacuum bag, will look into that

A vacuum bagging system may be suitable for this project. The vacuum creates uniform atmospheric pressure across the entire surface. You can laminate multiple panels at once.

I do not think a vacuum press will be sufficient to ensure a flat pressing. I would look for a 4 X 8 hydraulic cold press. If you use a slow setting adhesive you could load multiple sheets at a time.
Here is a typical pod press with a large daylight that could handle your job.

https://woodweb.com/exchanges/machinery/posts/551587.html

I use the vacuum Table on my CNC to clamp 4 x8 sheets pulling 22 inches of Vacuum Works very well