All true. I posted it as a bit of an exercise in the process I usually go through when analyzing whether a board needs to be changed (better than tapping or plucking or whistling). This was a bit of an extreme example where it was fairly clear early on but I thought I'd post it anyway. Often the data is more borderline than this. You're right, there isn't much point in measuring negative crown although I can imagine a situation in which someone set the downbearing excessively high by mistake (or ignorance) pushing the board negative when it might well have held up under a normal load. Not sure I've ever encountered that so I can't really say what happens once the board gets pushed through. Does it spring back when you take the load off and will it respond normally when you put a normal load back on it? I couldn't say. In this case with negative bearing and negative crown there wasn't really anywhere to go. David Love www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman Sent: Wednesday, June 22, 2011 9:06 PM To: pianotech at ptg.org Subject: Re: [pianotech] Soundboard Analysis On 6/22/2011 8:24 PM, David Love wrote: > This board clearly started out with negative crown > through that area. Hard to measure that with a string. Why would anyone want or need to measure negative crown? Once the string indicates it's negative, which it will do easily, the rest is more or less moot. >Even with some > rise in the board as indicated by the bearing change and the change at > the struts it was not enough to push the board into positive crown. The > board has oilcanned and is toast. My point... And generating more decimal points to indicate how dark the toast is won't change the conclusion. Ron N
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