Hello, The soundboard installation as explained to me is forcing a bit more from all around, because of the shape of the rim (belly ?) where the ribs and the board are glued, the coming back of the moisture in the assembly, and possibly the installation from the front with wedges or any acceptable method to force the board in place. On a the few Steinway I could measure I for sure never find a large crown in the long direction, but does it mean the approach is useless ? I believe that the place where the ribs are glued may be very tight, around the panel, I am unsure it should add a lot (was said that the little angle given top the belly was very important). But any method that gives a security against the glue sag (give) is a good one K. Fenner is well known there and we yet wait for something he described or say to be untrue - also because when he is unsure of something he don't present it like the definitive truth, as himself is considering that his views can enlighten or change with time ! The basic resistance and flexion model that where given in the PTJ 1968 journal (translation of a writing by Ulrich Laible, one of the teachers of the German Ludwisgburg school) are relatively basic and based on static material resistance, they don't take in account the placement of the neutral fiber in the assembly, the fact that the ribs are in compression and the panel in compression and tension, the thinner end of the ribs, and so on. A friend of mine have written a formula to compute the sag of a soundboard, but after evaluation it does not work either, because he see the assembly like a range of "T" made in an homogenous material. We where just talking about that today, with the conclusion that the computation are in fact useful only in the sense that if your ribbing is in the parameters computed, the soundboard for sure will be stiff enough. But so much more data may be taken in account if one want to compute the real down bearing counterforce available, that it should be a very complicated task. The list of parameters that should be added to obtain a figure that should be near the reality may be pretty important. I've been surprised that some rule of thumb does not exist (to my knowledge) on how to shape the end of the ribs to get the flexibility and the spring effect (and why the ribs where considered as rectangular all along in the precedent formula) Do some of you tone builders play with the ribs stiffness once they are glued on the panel , evaluating what you get by feel and craftsmanship ? before gluing the panel ? after ? Best Regards and thanks for your comments. Isaac OLEG Entretien et reparation de pianos. PianoTech 17 rue de Choisy 94400 VITRY sur SEINE FRANCE tel : 033 01 47 18 06 98 fax : 033 01 47 18 06 90 cell: 06 60 42 58 77 > -----Message d'origine----- > De : pianotech-bounces@ptg.org > [mailto:pianotech-bounces@ptg.org]De la > part de Ron Nossaman > Envoye : dimanche 20 juillet 2003 22:43 > A : Pianotech > Objet : Re: soundboardinstal again > > > > >I had lately a conversation with Claus Fenner. If I > understand well he was > >explaining about > > the way Steinway Hamburg installs their soundboards: > since the rim is first > >made they force the board > >for the last millimeters into the rim , push it, really > stress it into > >the rim , tight fit, no gaps > > and this should be the difference between Steinway and > other brands. That > >way in killer octave > >(should be the stiffest part of the soundboard) the board > can better resist > >to downbearing and > >produce this Steinwaysound. Or did I misunderstood this? > > > >Danny Boddin > >Ternat Belgium > > > No, you probably didn't misunderstand it as it was told to > you. You're just > accepting that Claus Fenner and Steinway are right when > they say anything. > It's been my experience that it is utterly unimportant > (except for looks) > that the edge of the soundboard contact the outer rim in > any way. The glue > joint between the panel and inner rim is what does the job. > It couldn't > hurt to fill the area with wedges and epoxy, but it's a lot > of time spent > on something that won't make a difference in the final > performance of the > board, and it most certainly won't help the killer octave. > > Ron N > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
This PTG archive page provided courtesy of Moy Piano Service, LLC