Back to the origional point of this thread... the article itself. There was a few things I found really interesting about the article. The experiment itself showed a few things I'd like to have a bit of clarifications on. When Ron put the newly ribbed (and still dry) panel in the restraining caul (if I may call it that) and allowed it to take on humidity, the thing didnt crown. This is as Ron stated to be expected given his basic postulate about the assembly not being buttressed to begin with. On the other hand the part of the panel/rib assembly being restrained is panel endgrain. As I have understood earlier discussions along this arch thread, compression failure of end grain far exceeding its ability to support the arch even if there was a real buttress was one of the main points argued against the arch idea. But the experiement would seem to show that the end grain did not fail at all and acted as a kind of reverse buttress if you will, preventing the panel from crowning when restrained. Then too is the point about the centerline of the rib/pannel assembly being below the buttress. This raises a nut that needs addressing. If the underside of panel itself when crowned actually does behave like the upper half of the rib in this respect... then it is expanded... stretched as it were along with the bending ribs upper half. But if that is the case... then this same underhalf of the soundboard has experienced a degree of tensioning because of that stretching. It would seem that tho the underside of the panel in general is under very much compression, this same compression is then lessened to some degree by the ribs stretching in the opposite direction. How one is to figure the net degree of compression in the panel then strikes me as difficult at best... but certainly seems worth knowing. Cheers RicB
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