Gene Nelson wrote: > ****Hopefully I can describe this so it makes sense: > As I consider how the radius are cut onto the ribs - pulled and clamped > into a caul mounted onto a sled on a table saw - the high point mark on > the rib (bridge location) is aligned to a mark on the caul on sled and > the finish height cut is made simultaneous with radius arc. The mark on > the rib (high point) may not be in the center of the rib. Example: on a > 12 inch long treble rib the high point may be 4 inches from the belly > rail and 8 inches from the inner rim. It would seem to me that the > radius circle should still be uniform??. It would also seem to me that > if the high point were centered on this 12 inch rib, the bridge would be > located so far away from it that there would be considerably less crown > available for it. Make any sense? > > Gene Not a bit (sorry). That's the pretty much universal description of *intent*, but doesn't have much of anything to do with result. Try it with a piece of scrap wood. Make a rib about 18", or a half meter (Can I butcher linear measurement systems like this without losing the logical point?), and put the high point of the CONSTANT RADIUS crown as FAR OFF CENTER as you can. Feather it, as you do, prop it up on identically sized blocks, and measure where the high point of the crown is. It will be, I guarantee, unless you made something other than a constant radius crown, in the center of the rib. It matters not how you hold your tongue during the measuring and cutting process, the high point of the resulting arc segment defined by a chord will always, always, always, pending the refutation of basic geometry, be in the center of the chord. This isn't something that's going to bow out to intuitive "understanding". It's part of the marrow of reality. I chose the half meter as a reasonably handy size that wouldn't waste unnecessary material, and would be easy enough to measure. You could make it 40 meters long to similar effect, but it would be marginally more expensive and difficult to produce. That's it. It's not my claim, by discovery, or my invention as a desperate attempt to be right at any cost. It's an observation of principle that has been known for thousands of years, in every corner of science but piano technology. I just think it might be time we caught up with the civilization that built the Parthenon. Ron N
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