I have been restoring a plywood boat approx 20yrs old & have noticed a
ridge in one sheet of ply running accross the sheet in a uniform
manner. I have removed paint down to the wood & everything seems OK,
no sign of damp or delaminating.
Is this quite normal for ply to do this or could there be an
underlying fault? If so is it best to just ignore it as it just seems
cosmetic to me. By the way its nowhere near the end of the sheet or
any other obvious weak point.

Thanx,
Graeme