David, what are you trying to illustrate in the picture? You have your rib bent to a crown radius that will never be seen in a real piano. 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 David Love Sent: Wednesday, July 13, 2011 8:49 PM To: pianotech at ptg.org Subject: Re: [pianotech] Measuring Crown Radius RN It made no point at all, and was a ridiculous comment since a panel wouldn't crown without a rib. It addressed nothing. Make some attempt to stay within reason. DL Of course an unribbed panel will crown. Dry it down and glue it to the rim and let it take on moisture. The expansion has to go somewhere. If the rim of the piano is beveled or if the board starts even marginally crowned upward it will continue to crown upward. Since you are arguing that the ribs that would have been bent by the expanding panel would have a negative impact on load support you would then expect that this crown, unribbed panel would support more of a load than a ribbed, crowned panel. Is that what you are saying? RN It's not a premise. It's elementary mechanics and physics. A flat rib will begin to support load as a beam only after it's pushed concave. If the panel is holding it up in a crown, it's not supporting anything. DL Of course. You could also say that a flat rib won't be pushed concave until it begins to support a load. But ribs on a CC board when the panel is glued into the rim are not flat any longer. They are bent. See the attached photo. Are you telling me that a flat rib bent into a crown and fixed at the ends won't support anything until it's pushed concave?
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