[pianotech] String elongation/Fenner article

Ron Nossaman rnossaman at cox.net
Fri Jul 31 12:04:58 MDT 2009


Jim Busby wrote:
> That was exactly my point, or the point I was trying to ask about with 
> this article. But if this has been discussed a dozen times on Pianotech 
> I shouldn’t have posted it w/o looking back.

Ok, I get it. The break% thing is what we discussed on 
pianotech, and break% and elongation are definitely tied 
together. The farther you stretch (elongate) a string, the 
higher it's break%, and the less reactive it gets to minute 
difference in stretch (elongation).


> While Fenner indeed talks about break % and the usual stuff, this notion 
> of length alone as “string elongation”, aside from any tension issue in 
> tuning stability, had me wondering… I’m studying it on my own (well, 
> with Vince Mrykalo) and think it is an issue worth looking at.

"Elongation" is misleading here. The fact that a longer string 
will change tension less with a given length change than will 
a shorter string with the same length increase strikes me as 
pretty obvious. Balancing the change differences with excess 
waste length may make the low break% string more stable, but 
it'll still sound like a low break% string.  In the June 1992 
PTJ, Fenner says that the shorter the back scale, the more 
stable the tuning, because the soundboard is constrained from 
moving. He also states that the longer the back scale, the 
harder the tuning is to accomplish, and the less stable it is. 
In practical application, I find this not to be the case. He 
also says soundboard rise and fall is primarily responsible 
for pianos going out of tune, and I also find this not to be 
the case. So to explore this stuff, we need to start with some 
clear basic premise, and take it apart for inspection and 
further clarification to establish it's validity, one premise 
at t time.

Ron N


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