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Joe Goss
imatunr@srvinet.com
www.mothergoosetools.com
----- Original Message -----=20
From: David Skolnik=20
To: pianotech@ptg.org=20
Sent: Saturday, March 30, 2002 10:07 AM
Subject: Re: Case separation or delamination question
Hi Terry -
At 08:52 AM 03/30/2002 -0500, you wrote:
This is a long post about rim delamination.
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.
If I understand you correctly, you are concerned that the rim =
delamination is causing the tonal deficiencies.
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.
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.=20
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.
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? Yes Who made =
the soundboard? Not relevant, other than to say it was done by =
experienced rebuilder 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!) No
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.
Fully evaluate crown and downbearing over the entire soundboard to =
better understand your soundboard's condition.
Terry, I'm just curious. How would you go about measuring the =
downbearing?
(:-!) See, I can't seem to get a good smiley (;-(=20
David Skolnik
=20
----- Original Message -----=20
From: "David Skolnik" <skolnik@attglobal.net>
To: <pianotech@ptg.org>
Sent: Saturday, March 30, 2002 1:09 AM
Subject: Re: Case separation or delamination question
> Thanks Del & Zen for your replies. First, a bit of an apology. I =
cross=20
> posted to the CAUT list because I suspected that there are some =
people who=20
> are on there exclusively, remembering afterwards that I, myself =
have=20
> sometimes found it confusing when the same thread subject is being =
carried=20
> on simultaneously on both lists, sometimes with cross posting, and =
at other=20
> times on only one or the other. I considered forwarding the CAUT =
responses=20
> to this list & visa versa, but suspect that will just make things =
worse,=20
> so, for now, if you're interested, there are some other responses =
on the=20
> other list as well.
>=20
> The piano in question is an old Steinway C (?) 85 note from about=20
> 1883. (There was either a recent posting or it was on someone's =
web site=20
> that I saw an excellent listing of old models and dates. I can't =
find it=20
> at the moment). The delamination between inner and outer rims =
goes=20
> completely around the perimeter. The visible gapping is generally =
from 1=20
> to 2mm. I only had a flat steel handled upright mute (.5mm or =
.020") to=20
> use as a feeler gauge & it tended to insert between 1 to 2 inches =
throughout.
>=20
> The piano was recently rebuilt (within the last year and a half). =
There=20
> have been significant tonal deficiencies, especially in the 5th =
and 6th=20
> 8ve. From the 7th rib up there is no apparent crown. I didn't =
notice the=20
> delamination when the piano first came back, but, in spite of a =
few months=20
> out of the year of rather low humidity (20%), I doubt that such a =
degree of=20
> separation would have happened in such a short time.
>=20
> The main question for me is, what design parameters are impacted, =
and to=20
> what degree, when there exists a significant amount of inner rim =
-outer rim=20
> separation of a unified rim design.
>=20
> At 09:35 AM 03/29/2002 -0800, Del wrote: (Edited)
>=20
> >Rim delaminations are usually not a matter of great concern--at =
least not
> >structurally--unless the delamination is evident for some =
considerable
> >distance or the affected area is expanding.
>=20
> >There is far less stress
> >on piano rims than is commonly thought.
>=20
> What are the sources of stress in a single rim construction? The =
initial=20
> bending creates the classic tension/compression stress. Spreading =
the arms=20
> to fit the pinblock relaxes some of that stress, but stresses the =
cured=20
> glue joints. Some stress is transferred from the strung plate. and =
perhaps=20
> some outward stress from the compression of the soundboard. Some =
of the=20
> stress is internal, some imposed. Would the acoustical properties =
of the=20
> rim change over time, as the internal stress dissipates?
>=20
> >With the now much more common style of rim construction in which =
the piano
> >is basically built on a separate inner rim with the outer rim =
being added
> >down the line somewhere, the most common problem involves getting =
the joint
> >between two rims just right.
>=20
> >Structurally and acoustically there is no advantage to either =
style of rim
> >construction as long as each process is done reasonably well. A =
glue joint
> >is a glue joint and it matters not whether the entire rim is =
formed in one
> >pressing or in two pressings that are later glued together. =
Having worked
> >with both I now have a preference for the so-called two-piece rim
> >construction. The resulting rim is at least as strong and the =
piano is much
> >easier to build accurately.
>=20
> So, what purpose does the outer rim serve, in a Steinway? Would =
you=20
> suspect any discernable difference between a Steinway built in the =
> traditional manner and one constructed with a 2 part rim? For =
that matter,=20
> when did Steinway begin unified rim construction?
>=20
> >In most cases I wouldn't be overly concerned about the small =
areas of veneer
> >delaminating often found in otherwise serviceable pianos. Keep an =
eye on the
> >area involved but, unless the delaminating is spreading, it's =
probably not
> >going to cause any real problems.
>=20
> >As part of the rebuilding/remanufacturing process the rim should =
be examined
> >for potential structural problems. If, during this examination, =
any rim
> >delaminating is found the gaps are filled with epoxy.
>=20
> In an older instrument such as the one I have described, I would =
assume=20
> that most, if not all of the original internal tension has =
relaxed. Unless=20
> the outer rim contributes to rigidity of the soundboard mounting, =
affecting=20
> crown and energy reflection, the only reasons I can see =
addressing rim=20
> separation would be either cosmetic, to prevent potential =
transient=20
> vibrations, or to keep it from getting worse. Have I =
misunderstood or=20
> misstated your position, or does this correctly reflect your =
thoughts?
>=20
> Thanks -
>=20
> David Skolnik
>=20
>=20
>=20
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