RC vs CC again

[Delwin D Fandrich]

----- Original Message ----- 
From: "Alan Forsyth" <alanforsyth@fortune4.fsnet.co.uk>
To: "Pianotech" <pianotech@ptg.org>
Sent: October 08, 2003 2:43 PM
Subject: RC vs CC again


> Del wrote;
>
> >>"do you suppose it somehow -- miraculously -- lost
> its desire to get itself straightened out?">>
>
> As an offshoot to this topic, what then happens to the wood fibres in a
> hammershank when we cast them with a heat source? They certainly have
lost
> their "memory" in this case. Would "time" under stress be a factor in a
rib
> losing it's "memory"?
>
> Just asking!
> Alan Forsyth


Ah, now we introduce an outside influence.

Yes, applied heat does soften the lignin (basically a chemically complex,
thermalsetting adhesive) and allows some permanent reorientation of the
wood fibers. We do not typically heat ribs sufficiently to either give them
crown or to remove crown once it is established however.

And yes, time under load is a factor. It is one of the reasons a piece of
wood under continual stress changes shape over time. But, while this is a
factor in why a compression-crowned soundboard assembly (and, though to a
much lesser extent, a rib-crowned soundboard assembly as well) will lose
crown over a period of years, it is not germane to the current discussion.

Del