This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Comments interspersed below: =20 ----- Original Message -----=20 From: "Delwin D Fandrich" <pianobuilders@olynet.com> To: <pianotech@ptg.org> Sent: Thursday, July 18, 2002 11:15 AM Subject: Re: Untapered Soundboard Ribs >=20 > ----- Original Message ----- > From: "Farrell" <mfarrel2@tampabay.rr.com> > To: <pianotech@ptg.org> > Sent: July 18, 2002 3:48 AM > Subject: Untapered Soundboard Ribs >=20 >=20 > > The Mehlin grand I worked on the other day had untapered ribs on its > soundboard. Ribs on other pianos are somewhat abruptly tapered near = the > ends. Is that so the panel will tend to move as one unit and flex = around the > perimeter - somewhat like a speaker cone might move with its firm cone = and > soft surround material that connects the cone to the basket (I kinda = don't > think this is really a good analogy). It would seem to me that = untapered > ribs are quite a departure from "the proper way to build a = soundboard". >=20 > You do raise some interesting questions. It is my belief that ribs in = the > 'modern' piano are end-tapered the way they are to accommodate the = practice > of compression-crowning. In this process the rib actually resists the > formation of crown--i.e., the rib wants to remain straight but is = forced > into a curve by the stress interface created by the expanding = soundboard > panel. The rib must be kept to a reasonably consistent height and = thickness > if the crown radius is going to be anywhere close to uniform. Interesting. That sure does make a lot of sense. Should work also. > Even as most manufacturers began converting from compression-crowning = to > rib-crowning techniques (or some combination of the two) the = traditions of > rib sizing and feathering carried over. Hey man, we gotta do it like the masters! > The problem, of course, comes at the parameter where the tall ribs = will > restrict the motion of the vibrating panel. More or less--considering = the > range of motion of the typical soundboard, however, there really isn't = a lot > of bending going on around the parameter of the soundboard. So, in = real > life, that untapered (un-feathered) rib may not matter all that much. > Indeed, it may well help through the killer octave region. > > > > If soundboards vibrate their various frequencies in small random > (seemingly) areas of the board... >=20 > Don't confuse reality with desirability. Just because the typical = soundboard > does break up into a myriad of miscellaneous resonances doesn't me = this is > the ideal. Or that this is desirable. >=20 > > ...why do we taper ribs like we do (the abrupt taper near the end). = Why > not an even taper along the entire rib? Or no taper? >=20 > Why not indeed. Have you ever seen the ribs on one of our soundboards? = It's > been some years since we've feathered anything in the conventional = manner. No I have not. I have seen the Walter grand - but I don't remember the = rib tapering. I'll just have to see your stuff sometime! Thank you for = your thoughts. > Del >=20 ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/3e/2d/90/75/attachment.htm ---------------------- multipart/alternative attachment--
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