[pianotech] Diaphragmizing

[erwinspiano at aol.com]

??? Dave
?? I had another thought about this. The Patent on this is 1936 sih. I've replaced boards from the middle 30s' that were supposed to be in this time crossover time ?frame and they showed evidence of thinning however?many panels from the 1920s?show evidence?of thinning as well. 
??? I believe part of the diaphramizing patent was a portion of the rim in the curve that was?elevated a bit so the board would not need to be pushed down as far during glue up. The idea was less stress or restriction on the soundboard. If my memory serves it sounds like they just thru diamprmizing into the mix although I think they were practicing this for a while in some manner. Of course...things evolve. They had some very good Bellyman in the factory during the 20's and from experience perhaps they cam to a conclusion as to the efficacy of thinning
?? I find most evidence of it behind the bass bridge & around the tail but also adjacent to the very top of the treble bridge there is a definite slope. The slope does not reach out toward the bridge very far. This slope, if not there, would allow the plate to sit?partially or potentially on the soundboard?instead of the dowells. Looks like a clearance issue
? Dale


-----Original Message-----
From: David Love <davidlovepianos at comcast.net>
To: pianotech at ptg.org
Sent: Sun, 25 Jan 2009 8:28 am
Subject: Re: [pianotech] Diaphragmizing



Many people do it and the practice has been Steinways for some time.  I'm
curious about when Steinway actually started the practice and since I
haven't taken out many Steinway soundboards that are newer I'm curious what
their current practice is and whether other makers historically have
employed this practice.  I always thin the boards I do in the bass section
graduating down to about 5 mm by the time one gets to the edge.  But farther
up on the bent side and in the treble I don't, neither at the belly rail.
While I understand the idea of creating greater flexibility in the bass
section for those low frequencies I'm wondering what the reasoning would be
for thinning higher up in the scale.  Also, if one is installing a cut-off
bar, as I do, then were you to thin the perimeter it presents some questions
about how to treat the cutoff area in the case where, as I tend to do, not
cut the panel there but leave it whole.  Early Steinway pianos that I have
taken apart don't seem to be thinned in that area and the thinning in the
bass section is less pronounced.  

David Love
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of V T
Sent: Saturday, January 24, 2009 9:17 PM
To: pianotech at ptg.org
Subject: [pianotech] Diaphragmizing


Hi David,

Darrell Fandrich used to do that on some of his pianos. Perhaps, he would
share some of his experience and knowledge.

Vladan

>Can anyone speak to the history, philosophy, current  practice and general
>effect in different parts of the piano of thinning soundboards around the
>edges also known as diaphragmizing?  
>
>David Love


      



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