Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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As you no doubt know, something in the process created stress in the laminated panel that was not strong enough to twist the entire panel but strong enough to twist the pieces you cut apart. PVA contains water, and there were a number of glue lines in the assembly. And cured PVA is still somewhat flexible, meaning it may not have the strength to resist stress in the lamination.
Moisture causes wood movement, more along growth rings than across them. The poplar core of your plywood may have been rotary peeled, along the growth rings. The added water would not be able to move out of the 3/4" lamination in only a few days, and the sprayed coating will only slow down the moisture movement out of the lamination.
I'm not familiar with aluminum phenolic, but it might be stiffer than two maple and thus able to counter the stress in the lamination. Or perhaps because wood is not perfectly uniform, and glue layers seldom perfectly identical, there just happened to be less stress in that lamination.
If 1/8" Italian bending ply isn't flexible enough, there is no shame in telling the designer the concept is not workable and show what is possible with the 1/8" Italian bending ply.
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