rear string lengths

[Erwinspiano@aol.com]

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          List
          Although there are many reasons for the usually generous sustain 
times heard on Mason &Hamlins all this talk of rear duplexes got my attention 
the other day as I tuned one of my recently bellied Mason A's. All the 
backscale lenths in the plain wire are generous. I found the sustain very 
good in the K- ovtave as is usual for these pianos with decent boards.  I 
also note that the first 9 notes of the first capo section had  tuned 
duplexes corresponding to a 6th partial and the rest of the section double 
octaves. By the way this 1915 ish piano had very good duplex location as all 
the half round duplex/bearing blocks were very well in tune and all I simply 
used the original  position when it was rebuilt.
    All this to say that the rear string lengths of the first nine notes were 
quite long. Starting at about 4 inches down to about three then back up to 
longer lengths again. Although these segments were fairly well in tune the 
greater attributing factor I believe is the long backscale lengths. Other 
contributing factors would be wide cases/boards, good scales (mostly), good 
bridge location in the center of the board etc.) (As a side noteRecent 
discussions on Mason a's very short bass backscale lengths didn't however in 
this case render the tone unacceptable by any means. Tail thinning helps 
greatly on these pianos with conventional belly's)
  Finally the question. What are adequate backscale lengths  capable of 
giving  increased freedom/sustain. The lengths in this case are much longer 
than the average stwy. It seems like 3 to five inches on any piano(in the 
capo) would allow more bridge and board freedom.
  If I removed the duplex on the average stwyL and changed nothing but the 
string lentghs.(forget the tuning) what would happen? 
     I'm looking for suggestions and expeience from whomever. 
           Thanks--Dale

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