How about treating the inner rim with a penetrating epoxy? Holes could be drilled and filled. From another perspective there were also pianos with rims that were not solid, Bosendorfer, I think I know of a Chickering. "From a design novices perspective, ribbing the panel at a 60' radius through the panel and 6% emc seems inadequate to form enough crown especially in the upper end of the piano. " Thanks to Dave L. for suggesting I re-examine my emc. ----- Original Message ----- From: "John M. Formsma" <john at formsmapiano.com> To: "'Pianotech List'" <pianotech at ptg.org> Sent: Saturday, April 15, 2006 6:32 PM Subject: RE: Buttressed Arch. Question for Ron N. > Rons, > > So, bear with one of the guys who feels a little slow in getting all this > through a thick skull...hitherto I've focused on servicing these pianners > rather than making the design better, although it's always been quite > fascinating. > > I think what you're saying is that mass in the rim and on the rim via the > plate is good. Right? > > Now, the impedance under consideration is the ability to resist energy from > the board into the rim where it's dissipated, if I'm getting it. So, more > mass = more impedance = more sustain, huh? > > OK, next. If more mass is good, what about the theoretical possibility of > having the most massive, densest material as a rim to which the board was > affixed somehow? Just for theoretical consideration, would that make it > better theoretically? > > Practically, what better material could be used than what is currently used? > I mean, it seems like you could actually get about anything to work, but the > heavier you make 'em, the less likely they would be bought b/c they would be > so difficult to move. > > Thanks from someone whose head impedance is pretty high. <g> > > John Formsma > > > Following on from Ron N's comments on the mass loading of rims, and its > > impedance benefits, I've suspected for some time that heavy plates help > > sustain. I think its one of the reasons why the Baldwin SD-10 is such a > > remarkable instrument. The benefit of using a denser timber such as rock > > maple for the rim may have as much to do with the mass increase as > > stiffness. > > I agree, both counts. Load 'em up. > > Ron N > > >
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