Chines and multi-piece rims

[Farrell]

My thoughts/questions are kinda running like Ed's here. How does a three piece case allow improved geometry of the soundboard in the treble area (allows you to start out parallel to the rear of the bridge at the treble end from the get-go?)? And how does it affect the bass end to better allow floating of the bass end of the soundboard?

Regarding Ed's questions about the massiveness and/or stiffness of the rim, with solid timber sections of rim, is it not the case that all we would need to do is increase size of these timbers and/or add framing until we have whatever mass/stiffness we feel we need? We know how to join two pieces of wood in a rather solid manner, so the fact that a rim is made of separate sections should be of no disadvantage. Keep in mind that one full side of all soundboards is a separate solid piece of timber - the belly rial (and even those are often more than one piece) - although I must admit that I have always assumed that this was the weakest part of the case.

Terry Farrell
  
----- Original Message ----- 
From: <A440A@AOL.COM>
To: <pianotech@ptg.org>
Sent: Sunday, March 03, 2002 6:43 AM
Subject: Re: Chines and multi-piece rims


> Del writes (and confuses me):
> 
> >The continuous bent rim has certain manufacturing advantages but it has
> >no acoustical advantages that I am aware of. 
>  <big snip>
> >So, having said all that, there is at least one compelling reason for my
> >use of a multi-piece rim: its potential acoustic superiority. I can better
> >shape the treble soundboard and I can more easily float the bass end of the
> > soundboard. 
>  
> Greetings, 
>    Perhaps I am reading it wrong,  but these two statements seem to be taking 
> different paths. Does "its potential acoustic superiority" refer to the 
> geometry it makes possible? 
>    I don't think we can discount the acoustical importance of the rims, since 
> they are not only massive, but are entrained via their connections in the 
> string-bridge-soundboard-case-plate-string -etc circle.  Wouldn't the 
> "impedance" of the rim have a measurable effect?  I know we can use uprights 
> with their jointed constructions as a case in point,  do they have the same 
> output as a continuous wrapped grand?  Would it be fair to draw comparisons 
> with the Lucite cased grand that has been on display( or did it have a wooden 
> inner rim?)
> Regards, 
> Ed Foote 
> (I have never installed a soundboard, or untwisted a case, but I have sure 
> sat in front of'em for a long long time)