1) Both the inner rim (or skeleton) and the outer rim are laminated up as a unit in a single stepped press. 2) It is inherently unstable. Yes, the ribs do act to remove crown as they try to straighten themselves out. Yes, at any time the MC of the board increases the rate of compression set accelerates and (often) compression damage occurs in the panel. ddf Delwin D Fandrich Piano Design & Fabrication 6939 Foothill Court SW, Olympia, Washington 98512 USA Phone 360.515.0119 Cell 360.388.6525 del at fandrichpiano.com ddfandrich at gmail.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Thursday, July 14, 2011 2:52 PM To: pianotech at ptg.org Subject: Re: [pianotech] Measuring Crown Radius At 16:22 -0500 14/07/2011, Ron Nossaman wrote: >In CC crowning, the panel is dried down, then glued to flat ribs. >Panel expansion as it takes on moisture then bends the ribs into a >crown. The piano case isn't involved in the process, and the ribs >needn't necessarily be dried down. Whether they are or not would surely make quite a bit of difference. If the case is not considered (by Steinway's for example) to be involved in the process, why do they glue the case to the rim before fitting the soundboard, thus causing themselves a lot of tiresome work that could be avoided if they glued down the soundboard before attaching the case, as many, if not most, makers do? However that may be, the method seems to me inherently unstable. For one thing the bars (ribs) will ever afterwards be acting to remove the crown, won't they? If at any time the moisture content of the board rises to a point where the board proper is crushed, then the bars will be keen to relax and pull down the crown. JD
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