"Max" writes:
wrote

Most of the time when you see twisting or wracking it can
be minimized by reorienting the victims in the clamps.

However, when teaching others the art of the glue up, almost without
fail the most likely culprit in their glue up failure is placing the
clamps and material on an uneven surface to glue up. And uneven table
top, gluing on saw horses, etc., bring a whole different dimension non
parallel clamps.

When I glue something up in the field that requires this kind of
clamping, I actually level my "table" on the sawhorses by carefully
leveling the material I am using for a top.

This cuts out most of the problems.

Robert

Bingo. It took me awhile to learn that but once I did it solved a lot
of frustration.
I built an assembly table with legs that could be adjusted to level.

Max

Is that really necessary?
I just have been using a 1/2 sheet of 3/4" plywood that is pretty darn
flat so that all ends of each parallel clamp rest on the same flat
surface. Then in turn the bases of each clamp are paralle to this
surface as is the piece being clamped.

Within reason, it doesn't matter whether this plywood top is level with
the ground or not as long as all clamps fully rest on its surface...

Am I missing something?