>I am replacing a soundboard in a S&S 1890s upright, more for the experience >than anything else. The original ribs are flat. I was considering machining >a crown of 60' radius into them. But this is going to seriously alter the >dimensions of the rib if I keep the opposite side of the rib flat. > >Do I: > >1) Don't crown the ribs. > >2) Don't crown the ribs so much. > >3) Put the arch on both sides of the rib, there by maintaining the cross >section. > >4) Or what? > >Thanks for any input. > >Andrew Remillard Just reproducing what was there, with crowned ribs, would be the easiest route. You could add a millimeter or so to the rib height to compensate for the crown machining, and feather to accommodate the new top profile, and be well in the ball park. Just relieving the panel of the necessity of having to both bend the ribs and support string bearing, by letting the ribs carry some positive load, should help a lot. Further refinements get a lot more complicated very quickly. Ron N
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