Facts and nots : was Recommend Rebuilder?

[John Ross]

Thank you gentlemen, for helping me.
What got me started, was that Steinway considers the compression ridge, a 
normal occurrence.
To me it doesn't even look right, having this ridge, running down the 
soundboard, for all to see.
It definitely tends to look like a flaw.

John M. Ross
Windsor, Nova Scotia, Canada
jrpiano at win.eastlink.ca
----- Original Message ----- 
From: "Farrell" <mfarrel2 at tampabay.rr.com>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Friday, March 23, 2007 10:27 PM
Subject: Re: Facts and nots : was Recommend Rebuilder?


>
> ----- Original Message ----- 
>> What I was thinking was, that if boards are glued together, then the 
>> compression takes place. If some of those wood fibers compress, and form 
>> the ridge, then the measurement, is less than if that portion had not 
>> compressed more than the rest, so the crown would be less. Or is the 
>> crown the same, because of the ribs, and the board just came in from the 
>> edges?
>
> I think I understand your question. No, the board doesn't move in from 
> anywhere. It is glued (presumably) to the ribs and stays put. Yes, you are 
> correct thinking that the ridge, a product of crushed wood, is no longer 
> under compression (or less so anyway) and that small segment of panel will 
> support less crown. So yes, presumably the crown would be reduced.
>
> But realize also that compression can damage wood cells outside of the 
> ridge zone. Ridges formed on a panel suggest that the entire soundboard 
> panel has been subject to some fair bit of compression, and presumably 
> some amount of unseen wood cell damage (compression set). Likely crown has 
> been reduced by some of that panel damage also.
>
> Terry Farrell
>
> BTW, after reading Ron N's response, I now realize what you were asking 
> about "figuring out" the crown - you meant how do they calculate what to 
> do during manufacturing to produce a desired amount of crown. I think Ron 
> answered that question and your others quite eloquently.
>
>> I hope someone, knows what I am trying to say, as I am having a problem 
>> expressing myself. Obviously a field, I have not studied.
>> John M. Ross
>
>