Ron. I think what Peter is doing here is inducing a small amount of crown by gluing a flat rib to a flat panel in a curved caul at ambient RH. And of course, this will produce a small amount of crown. He then dries the board down and glues in into the piano. It would appear that he is relying on the rigid-rim-supporting-the-crown theory to keep the board crowned after it expands a bit with the increased RH. Obviously, there are a few of us that do not feel that theory holds much water, let alone crown. Perhaps a tension resonator is needed? Different folks will read the same things and come up with radically different understandings. Terry Farrell ----- Original Message ----- From: "Peter Kestens" <peter.kestens2@pandora.be> To: "'Pianotech'" <pianotech@ptg.org> Sent: Tuesday, December 17, 2002 12:53 PM Subject: RE: Soundboardcrown > > Peter, > > From your description, I wouldn't expect your board to have > > done anything > > else but go flat when you dried it. > > I do not say and don't have said the board was going flat by drying it. > I only eye-checked it and saw that some crown has disappeared compare > whith the crown the board gets when it comes out of the press. I don't > have checked it with a straight piece of wood. It was just by eye. > > I really doubted it to dry it before gluing on the ribs; but because > I've placed last year a new bord in a Bechstein (no, I did not made it > myself) and because I did not have much crown either with that board and > because this piano sounded really very nice, (believe me I'm not the > only one who's saying this and who have heard it sounding) I've not done > it. I dried this soundboard also before gluing it in the piano, for the > reason you can read one alinea down. > > >Why would you dry it to > > glue it in the > > piano when you apparently didn't to glue on the ribs? I don't > > understand. > It is not that difficult to understand. When you dry it, it became > flat to place it in the piano; when it's done, because of the higher > humidity of the environment, it has to swell, ie taking an arc because > it can't move freely anymore due to the glue. > > > As Del said, I hope you can get the ribs off without > > destroying the panel > > so you can start over again. In the four years or so that > > you've posted to > > the list, at least a month's worth of reading has been posted > > on soundboard > > crowning methods and expected results. Please go back and > > read some of this > > stuff, particularly the differences between rib crowning and panel > > (compression) crowning. > > Believe me, I do understand it (Just for explanation: I've read and > studied the compilation of articles published in the Journal the PTG has > done concerning soundboards). > Rib crowning helps you getting more consistant soundboardcrown for a > longer period of time, but for the sound, using either crowned or flat > ribs does not change anything to the sound, as far as I know. I only > know that using compression crowning needs more force to bend ribs and > board and, I have to say, I hope that using this method gives more > strenght and stiffnes to the ribs (ie, soundboard). Isn't this the > ultimate goal? Please do correct me if I'm wrong.
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