I've got a Yamaha studio upright that continues to break strings at D3 (wrapped bichord). The speaking length is 890mm, the core wire 14 gauge and the outside wrapped dimension is .058". My spread sheet shows that at 69% BP but my own formula might be low. Any string makers care to input here? It seems to me it's got to be too high. David Love www.davidlovepianos.com
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