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Hi Terry -<br>
At 08:52 AM 03/30/2002 -0500, you wrote:<br><br>
<blockquote type=cite class=cite cite>This is a long post about rim
delamination.</blockquote><br>
Actually, it only seems long, most likely because I used the shorter line
width that people seem to prefer, and because I use too many commas. I
also try to save space by not using smiley faces, but I think them a
lot. Also my apology took up a few lines.<br><br>
<blockquote type=cite class=cite cite> If I understand you
correctly, you are concerned that the rim delamination is causing the
tonal deficiencies.</blockquote><br>
<font color="#0000FF">That WAS the point of my original question. By the
time of the post to which you responded I was trying to confirm and
clarify my understanding of what Del had said, which, overall, left me
feeling that this might not be as big an issue as I had first
thought. I offered as little information as I thought was necessary
to focus on that question, but, judging from a few of your subsequent
comments, that may not have been adequate.<br><br>
</font><blockquote type=cite class=cite cite>I'm no rim professional, but
I suspect all you need to do with this rim is to flip the piano over and
fill the little rascal gap with West System epoxy.
</blockquote><font color="#0000FF"><br>
I haven't the means to simply flip this 8' sucker over. (Good thing it's
only 85 notes) Even if it hadn't just been rebuilt, I would want to
know that it was likely necessary before I undertook the
expense.<br><br>
</font><blockquote type=cite class=cite cite>Ok, so now you have the rim
taken care of. Time to consider the cause of the tonal deficiencies. You
have a flat board with a dead treble. You mention the piano was rebuilt.
New soundboard? <font color="#0000FF">Yes</font> Who made the soundboard?
<font color="#0000FF">Not relevant, other than to say it was done by
experienced rebuilder</font>
Original 119 year old Steinway soundboard? Yikes! If that is the case, I
would consider focusing on the need for a new soundboard. (This kinda
sounds like the situation to me!)
<font color="#0000FF">No</font></blockquote><br>
<font color="#0000FF">The question for me was whether there was any
reason to suspect that the delamination would likely have contributed to
the apparent lack of crown in a newly installed board.<br><br>
</font><blockquote type=cite class=cite cite>Fully evaluate crown and
downbearing over the entire soundboard to better understand your
soundboard's condition.</blockquote><font color="#0000FF">Terry, I'm just
curious. How would you go about measuring the
downbearing?<br><br>
</font>(:-!) See, I can't seem to get a good smiley (;-( <br><br>
David Skolnik<br><br>
<br><br>
<br><br>
<br>
<blockquote type=cite class=cite cite> <br>
----- Original Message ----- <br>
From: "David Skolnik" <skolnik@attglobal.net><br>
To: <pianotech@ptg.org><br>
Sent: Saturday, March 30, 2002 1:09 AM<br>
Subject: Re: Case separation or delamination question<br><br>
<br>
> Thanks Del & Zen for your replies. First, a bit of an apology. I
cross <br>
> posted to the CAUT list because I suspected that there are some
people who <br>
> are on there exclusively, remembering afterwards that I, myself have
<br>
> sometimes found it confusing when the same thread subject is being
carried <br>
> on simultaneously on both lists, sometimes with cross posting, and
at other <br>
> times on only one or the other. I considered forwarding the
CAUT responses <br>
> to this list & visa versa, but suspect that will just make
things worse, <br>
> so, for now, if you're interested, there are some other responses on
the <br>
> other list as well.<br>
> <br>
> The piano in question is an old Steinway C (?) 85 note from about
<br>
> 1883. (There was either a recent posting or it was on
someone's web site <br>
> that I saw an excellent listing of old models and dates. I
can't find it <br>
> at the moment). The delamination between inner and outer rims
goes <br>
> completely around the perimeter. The visible gapping is
generally from 1 <br>
> to 2mm. I only had a flat steel handled upright mute (.5mm or
.020") to <br>
> use as a feeler gauge & it tended to insert between 1 to 2
inches throughout.<br>
> <br>
> The piano was recently rebuilt (within the last year and a
half). There <br>
> have been significant tonal deficiencies, especially in the 5th and
6th <br>
> 8ve. From the 7th rib up there is no apparent crown. I
didn't notice the <br>
> delamination when the piano first came back, but, in spite of a few
months <br>
> out of the year of rather low humidity (20%), I doubt that such a
degree of <br>
> separation would have happened in such a short time.<br>
> <br>
> The main question for me is, what design parameters are impacted,
and to <br>
> what degree, when there exists a significant amount of inner rim
-outer rim <br>
> separation of a unified rim design.<br>
> <br>
> At 09:35 AM 03/29/2002 -0800, Del wrote: (Edited)<br>
> <br>
> >Rim delaminations are usually not a matter of great concern--at
least not<br>
> >structurally--unless the delamination is evident for some
considerable<br>
> >distance or the affected area is expanding.<br>
> <br>
> >There is far less stress<br>
> >on piano rims than is commonly thought.<br>
> <br>
> What are the sources of stress in a single rim construction? The
initial <br>
> bending creates the classic tension/compression stress.
Spreading the arms <br>
> to fit the pinblock relaxes some of that stress, but stresses the
cured <br>
> glue joints. Some stress is transferred from the strung plate. and
perhaps <br>
> some outward stress from the compression of the soundboard.
Some of the <br>
> stress is internal, some imposed. Would the acoustical
properties of the <br>
> rim change over time, as the internal stress dissipates?<br>
> <br>
> >With the now much more common style of rim construction in which
the piano<br>
> >is basically built on a separate inner rim with the outer rim
being added<br>
> >down the line somewhere, the most common problem involves
getting the joint<br>
> >between two rims just right.<br>
> <br>
> >Structurally and acoustically there is no advantage to either
style of rim<br>
> >construction as long as each process is done reasonably well. A
glue joint<br>
> >is a glue joint and it matters not whether the entire rim is
formed in one<br>
> >pressing or in two pressings that are later glued together.
Having worked<br>
> >with both I now have a preference for the so-called two-piece
rim<br>
> >construction. The resulting rim is at least as strong and the
piano is much<br>
> >easier to build accurately.<br>
> <br>
> So, what purpose does the outer rim serve, in a Steinway?
Would you <br>
> suspect any discernable difference between a Steinway built in the
<br>
> traditional manner and one constructed with a 2 part rim? For
that matter, <br>
> when did Steinway begin unified rim construction?<br>
> <br>
> >In most cases I wouldn't be overly concerned about the small
areas of veneer<br>
> >delaminating often found in otherwise serviceable pianos. Keep
an eye on the<br>
> >area involved but, unless the delaminating is spreading, it's
probably not<br>
> >going to cause any real problems.<br>
> <br>
> >As part of the rebuilding/remanufacturing process the rim should
be examined<br>
> >for potential structural problems. If, during this examination,
any rim<br>
> >delaminating is found the gaps are filled with epoxy.<br>
> <br>
> In an older instrument such as the one I have described, I would
assume <br>
> that most, if not all of the original internal tension has
relaxed. Unless <br>
> the outer rim contributes to rigidity of the soundboard mounting,
affecting <br>
> crown and energy reflection, the only reasons I can see
addressing rim <br>
> separation would be either cosmetic, to prevent potential transient
<br>
> vibrations, or to keep it from getting worse. Have I
misunderstood or <br>
> misstated your position, or does this correctly reflect your
thoughts?<br>
> <br>
> Thanks -<br>
> <br>
> David Skolnik<br>
> <br>
> <br>
> </blockquote></html>