In addition to Del's comments. >How significant is the stiffness added by the crown? >In other words, in a rib-crowned board, how much stiffness is provided by >the ribs (beams) and how much by the board (arch). >I suspect that most of the stiffness is provided by the ribs (no evidence >though) so please share your experiences. In a rib crowned and rib supported board, maybe 95%-100% of the stiffness comes from the ribs. In a compression crowned board, probably somewhat over 120% of the stiffness comes from the panel, since the ribs supply negative stiffness and crown support. A rib crowned but panel supported board is somewhere above 0%, and under 100%. And do forget about the arch. It still doesn't work that way. Ron N
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