> I'd also like >to know if there is some way one can "see" this by examining a soundboard >(aside from compression ridges; which I suppose could actually occur in a rib >crowned board as well when it comes right down to it). > >Richard Brekne Del probably has more details, but I have a couple of observations. Since the deflection resistance of a rib is directly related to it's width, and the cube of it's height (height^3), compression crown systems will tend to have ribs that are wider than they are deep, where rib crowned systems tend to have ribs that are deeper than they are wide. Other than that, computing the string bearing loads on the existing rib scale can give you a pretty good indication of whether the rib dimensions are capable of supporting bearing load without the panel doing all of the work (more math... lots of it. In an old Knabe I rebuilt early this year, the top five ribs were built up in two layers. The main body was flat along it's length, and had a thinner strip glued on top, that was about 6mm thick in the center, and 2 or 3mm at the ends. These pretty much had to be crowned ribs. Also, Both Yamaha, and Kawai crown their ribs. Ron N
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