This is a great discussion!! I thought I was a bad tuner after tuning in the NW for 15 years where this didn't happen. Right before winter semester started, I got really busy tuning pret-near everything I could get my hands on. Then, when all the NASM (accredidation folks) were to come, all the pianos sounded like crap! Humidity was 35% when I tuned, or so and then it dropped drastically to between 20-24% even as low as 13% for about a week during a cold snap(right before they came). Behold, the center strings were kinda close, although perhaps down 8-10 cents, but the left strings were sharp and the right strings were flat. The bass/treble break was horrible! I'm wondering, also, how soundboards, bridges, and strings behave to these changes. It's obvious that it happens everywhere and glad to know it's not just me!! :>) I've also found that the pianos somewhat "recover" when the humidity comes back up to where I started. Summertime is a different story! How have you all found unisons to behave....I realize the pianos will, in general, go sharp to 442 or so... Thanks Paul "Ed Sutton" <ed440 at mindspring.com> Sent by: caut-bounces at ptg.org 02/19/2009 12:34 PM Please respond to Ed Sutton <ed440 at mindspring.com>; Please respond to caut at ptg.org To "Jeff Tanner" <tannertuner at bellsouth.net>, "College and University Technicians" <caut at ptg.org> cc Subject Re: [CAUT] Detuning phenomenon; was: How long to stabilize?? Darned if I know! Lateral is what I'm imagining. It will depend on the hitch pin location. For the most part the change would probably be the same, front and back, since left sides of the trapezoids will tend to both face the same way relative to the bridge movement. This might account for the strings that are odd men out in the detuning pattern. Do you think the string slips past the bridge pins on, say, a 6 cents pitch rise? I see this happenning in pianos which were not played during the humidity change, so I don't thing the strings were rendered past the bearing points. Will it go back in tune if the humidity changes back. I don't know. Perhaps so if we are only talking about, say, a 2 cent pitch change. I have no idea what kind of lateral pressures would be involved, or if the soundboard wood is capable of generating it. For an even wilder thought, consider that if the bridge shrinks or expands enough, the angles of the bridge pins will change! Probably more productive to think about changes in bridge cap thickness. Ron Nossaman may be able to send some statistics about his laminated bridge caps. He also lives in pitch adjustment hell, so may have more experience to share. Ed ----- Original Message ----- From: Jeff Tanner To: Ed Sutton ; caut at ptg.org Sent: Thursday, February 19, 2009 1:02 PM Subject: Re: [CAUT] Detuning phenomenon; was: How long to stabilize?? You're referring to the shape created between the capo and the speaking length bridge pins, and you are speaking of a lateral shift rather than vertical, correct? If that was all that was involved, your theory makes sense. But from the non speaking length pins to the hitch pins, wouldn't the reverse be created, somewhat cancelling it out? The overall tension will eventually equal back out after a shift, right? How would such changes in tension not also somehow affect the center string, it being also either shared by the left or right unison? Just thinking with you. Tanner ----- Original Message ----- From: Ed Sutton To: caut at ptg.org Sent: Thursday, February 19, 2009 12:40 PM Subject: Re: [CAUT] Detuning phenomenon; was: How long to stabilize?? Would a small shift of the bridge to one side effect the left string more than the right, since the strings are not perpendicular to the line of the bridge pins? The outer strings create a long trapezoid, thus a shift of position would increase the tension on one and decrease it on the other. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut_ptg.org/attachments/20090219/131664b5/attachment.html>
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