[pianotech] Yamaha Upright String Breaker

[Ron Nossaman]

On 1/8/2011 1:04 PM, David Love wrote:
> 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.

I get 69% too, and while I'm not a string maker, I call it too high too. 
I know at least three makers who would complain immediately and loudly 
if I specified something like this in a custom set.
Ron N