setting up for installing soundboards

[Doug Hershberger]

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Del,
   Thank you for your response. I was the one who really posed the =
questions, thinking he may be interested. We did have a conversation =
about compression versus the other method though. He is way more =
experienced about these things than I am and he is for sure not rushing =
into it. I am sorry I brought it up if it has already been kicked around =
to death. I will check the archives. I think his original idea was to =
use a method that Claire Davies came up with because it was fairly easy =
for a small shop. Just in the couple of responses I've got though I =
would urge him to use caution about the type of technique he uses be it =
compression or the other.
Doug Hershberger,RPT
Aliso Viejo, CA
  ----- Original Message -----=20
  From: Delwin D Fandrich=20
  To: pianotech@ptg.org=20
  Sent: Saturday, January 08, 2000 9:07 AM
  Subject: Re: setting up for installing soundboards



    ----- Original Message -----=20
    From: Doug Hershberger=20
    To: pianotech@ptg.org=20
    Sent: January 07, 2000 2:22 PM
    Subject: setting up for installing soundboards


    Dear List,

    My questions to those of you with experience are as follows;
    1. what are your thoughts pro/con on atmospherically crowned boards

    It is the so-called "traditional" method of crowning soundboards.  =
However, by even the very early 1900s, designers and builders were =
discovering its limitations.  See Wolfenden's book.

    The basic limitations are:
        1)    The results are highly dependent on variabilities in =
atmosphere and wood.
        2)    It places extremely high stress loads on the wood fiber =
leading to rapid breakdown of same.
        3)    Performance is unpredictable.
        4)    Life span is unpredictable.



    2. Is the other method, radiusing the ribs and pressing the =
ribs/board into a caul of some sort?

    Yes, this is the other method.  Or some combination of the two.



    3. (this one is my question) What do they mean when they say 60 ft =
radius as it applies to soundboard crown?

    Just that.  In theory, at least, the radius of the curve of the =
soundboard along the rib is 60 feet (approx. 18 m).  Someone, somewhere, =
has decided that this amount of crown was the "correct" amount.  It =
rarely -- if ever -- works out in practice and even if it did, the =
theory is incorrect.



    He seemed to think that Steinway uses the atmosphere type method. I =
told him when I was there I didn't remember which method they used but =
they had a very expensive machine for precisely cutting around the =
perimeter of the board so that it would tightly fit the inside of the =
rim. Maybe that tight fit, plus gluing onto a angled shelf, plus =
diaphragmatic taper all contribute to their boards holding their crown.=20

    That is the method used by Steinway (unless they have changed their =
process in the past several years).

    Yes, Steinway does have a wonderful machine for trimming the =
soundboard to fit the rim.  This has nothing to do with forming crown or =
with sustaining it, however.  Nor does the angled shelf (inner rim).

    Thinning the soundboard panel through the treble section actually =
reduces the compression-crowned soundboard's ability to maintain crown =
over the long term.
    =20
    I might mention that these are some pretty basic questions.  Usually =
when a technician moves into soundboard replacement they have already =
been answered.  It might be wise for your friend to do some serious =
studying before tackling a project like this.  It is very costly to =
equip one's shop for soundboard work -- whether you purchase the =
necessary tools or purchase them, it is still going to be expensive.  =
Then there is the performance of the finished product to consider.... =20

    Regards,

    Del

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