Sort of. A 15' radius may be fairly common but only in the high treble where the shortened ribs produce a total crown of only 1-2 mm. While there are different approaches by those doing rib crowned boards, it's not unusual to design them so that there is only about 25% of the original crown remaining after they are loaded. That's pretty much flattening it and there isn't really a problem with that. The issue is how much the spring will compress by a certain load more than the residual crown. That's why measuring crown on a strung board as an indication of soundboard health is pretty meaningless. The difference in crown between the strung and unstrung board along with the calculated load will tell you much more about what the board is capable of tolerating. David Love davidlovepianos at comcast.net www.davidlovepianos.com 15-foot radius crown is not exaggerated, but rather commonly found in RC&S soundboards. A panel in a soundboard with that kind of crown certainly would have some significant degree of compression in it if it were to be flattened - but why on earth would anyone want to flatten it? I don't get my soundboards anywhere near flat after stringing. Terry Farrell
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