For clarification please. Are you saying that as the panel takes on humidity the ribbed assembly will experience a reduction in crown... and not increase ? RicB So the assembly takes on moisture... not only does the rib expand as a result by but a negligeable amount but whatever expansion there is will tend if anything to make it bend downwards and *_reduce the crown_.* ......and there will be significant expansion, will result in compression of the wood within or beyond the yield point, but any power it might have to make any difference to the crown will be _*completely** **negated by the action of the rib and the forces to which this is subjected.*_
This PTG archive page provided courtesy of Moy Piano Service, LLC