Terry, I'm looking through some posts from the last weeks and I'm wondering if I might be able to see these drawing you're talking about. Greg Farrell wrote: > Dear Pianogeometrical Wizzes: > > Greg Newell is causing me problems. He is making his first soundboard, and > he caused me to lay awake half the night diagramming 60-foot arcs, fire-hose > air clamps, clamping tables, etc. Geesh! Don't people ever think of the > ramifications of their actions? > > Anyway, using my CAD program to draw some arcs for making rib clamping > cauls, I drew an eight-foot long arc with a 60-foot radius (common arc for a > soundboard). Looking at the crown of such an arc over an eight-foot span, I > get 1.6 inches of crown. On a five-foot span I get 0.63 inches of crown. > This seems excessive (isn't an unstressed new board supposed to have about > 1/4" - 3/8" of crown in the middle?). Or is it that on the rib-crowned > board, you cut the rib to the aforementioned arc, glue it to the board in a > caul of the same arc, and when removed from the caul the naturally flat > board help the assembly to straighten out a bit to where it has the > "?normal?" 1/4" - 3/8" of crown? > > Am I making a boo-boo somehow with my drawing? > > Terry Farrell -- Greg Newell mailto:gnewell@ameritech.net
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