---------------------- multipart/alternative attachment >>I am assuming that a serious sound board will be rib crowned, but a >>laminated all spruce panel with rib crowning must surely be an >>excellent combination. > >You bet. A wonderful combination. I didn't say it very well, but I >was speaking, as I think Del was, of just the difference in material >stresses between the destructive compression levels in a panel >supported crown, and the much more benign stresses in rib supported >crown, since spruce takes bending stresses much better, and for much >longer than compression. I presume a laminated panel wouldn't be >called upon any more than a solid panel for supporting string >bearing by panel compression in a rib crowned system. Though, as you >point out, it certainly could be with less cumulative damage than a >solid panel. That's all I meant. I understand what you meant, and agree thoroughly with you both. >>I am assuming that any piano maker worth his/her salt will be using >>the RC process for crown. I cannot understand how anyone who claims >>to be serious about piano manufacture would use compression >>crowning. > >Likewise, though load analysis of the rib sets being used and the >bearing loads being placed on them (of those few I've checked) >indicate to me that the panels are still carrying a significant >percentage of the bearing load, even in some (most???) rib crowned >boards. Exactly. I am building and testing five inch wide strips of panel with one rib glued under it, set up as it might be in the piano (mounting it on a steel section of RHS - to fix the ends prior to load testing), to check on deflection under load, and to gain some insight into the relative load carrying of the two, ie. the crowned rib and the panel compression. If we shape a rib so that the top profile has a 7 mm rise while the bottom edge is straight, and after gluing a panel at 7% to the rib it rises a further 1 mm in the middle when the panel normalises - if it is loaded down such that the rib sinks out 3 mm it stands to reason that the load is being shared by the rib and the compression in the panel. The big question is what do we want between the two. Still thinking about this over the next week. This has been an interesting thread. Ron O. -- _______________________ OVERS PIANOS - SYDNEY Grand Piano Manufacturers Web: http://overspianos.com.au mailto:info@overspianos.com.au _______________________ ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/4b/86/91/d5/attachment.htm ---------------------- multipart/alternative attachment--
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