Hi Ron, Think of the plate as a lever. a very small change in angle at the point of contact with the rim makes a large difference in pitch at the string. Any easy experiment (or mistake LOL) that many of us made when we were starting out was to do a pitch correction and then tighten the plate. As for bridge *twist* affecting smearing of unisons the treble side string is the shortest tail length so *if* (and goodness knows I don't know the answer) there is a counter clockwise *twist* then the bridge pins would cause a greater pitch change on the shorter string. Next time I encounter this...I may try to do something with the front duplex area. I envisage measuring the treble side string and then giving the capo bar a *tap* with a hammer to release friction and then remeasure the right string. Could you Ron make a list (or add to) in point form of the various factors that *may* be changing as humidity rises. soundboard *curl* bridge *roll* bridge *twist* (if there is any) rim and frame shape change causing plate distortion: plate angle plate position nose bolt rise At 07:08 AM 08/22/2000 -0500, you wrote: >>Hi Ron, >>My hunch is that the plate is moving *more* than the soundboard...in the >>area of c7 for example. > >Ok, I'll bite. Explain why the plate would move more than the soundboard, >and why that would more reasonably account for this unison smear. > > > >>Another hunch is that the upwards movment of the >>sound board (which is an actually arching) causes a vector of force to >>twist the bridge counter clockwise. > >The bridge does tilt forward and backward as it rises and falls because >it's curved, and the center will move farther than the low end, and much >farther than the treble. It's not just in one direction, and I don't see >how this could have any effect on your smear. > > > >>Lets try to consider each possible factor and with a *thought* experiment >>decide whether it would cause pitch to rise or fall. Then if we add all >>theses compenents perhaps some cause and effect could be seen for the >>smearing of the unisions--other than the broad brush of humidity. > >Go for it. I've told you what I think, and why. > >Ron N > > Regards, Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. Tuner for the Saskatchewan Centre of the Arts drose@dlcwest.com http://donrose.htmlplanet.com/ 3004 Grant Rd. REGINA, SK S4S 5G7 306-352-3620 or 1-888-29t-uner
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