[pianotech] Soundboard Analysis

[David Love]

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