What's the back scale length of A-0? 95mm Not an awful lot. Is that all the room there was? >>>>No but I was advised to have 90 mm as a minimum. Probably a bit gun shy. Bass rescaled? Only slightly - reduced spl to get slightly longer tail lengths. What was the original A-0 back scale? >>>>I believe it was 70mm What's the core diameter of A-0? .058 Still fairly stout. >>>My mistake on the core wire it is really .061" - sorry about the >>>misinformation. I'd say it's likely a combination the board being too stiff, with the back length, and core diameter contributing. Up to about 6-1/2' (200cm) I float the tail around the low bass too. The bridge is for sure clearing the edge of the plate, right? >>>>Yes, double checked and positively clears the plate. I recently had an embarrassing reminder of how easily that can happen. What "design" board did you build? >> Radius cut ribs - 60 ft in the bass and tapering to the treble - 16 >> total. Made from quartered Sitka. Glue up at around 6 to 6.5 mc. > What method did you use to determine the count and dimensioning of the ribs? >>>>I calculated the downbearing force of the strings at every unison based >>>>on what I thought the bearing would be in the end when loaded. Spaced >>>>the ribs to support this and started with the end of bridges and then >>>>the calculated # of unisons with fudging as needed to clear nose bolts. Kept the ribs taller than wide and spaced them on the unisons so that a known load was applied to each rib. Designed rib hight and width so that calculated deflection and max load capacity looked good. Deflection ranged from .250" in the lo bass, .450" at rib #7 and .036" at the top treble. Also considered available crown based on radius and how much of it I wanted to use for bearing. The load carrying capacity of the ribs ranged from 27 lbs in the lo bass, 52 lbs at rib #7 and 90 lbs at the top treble. The board was not cut off in the bass but the inner rim gluing surface was built up with epoxy and veneer to accomidate the part of the board that did not want to go down on the rim without a struggle. Why not, and why? >>>>Customer would not be happy. The build up I thought was the next best >>>>thing. Board thickness is 9mm - on the fat side - no diaphraming. Again, why >>>>No good answer for that one. One thought along this line that I did have was my experience when I visited David Rubenstein's 12' piano. It has a 1/2" thick board and the tone is very dark with tremendous power - I really liked it. This probably influenced me somewhat. Gene >
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