Case separation or delamination question

[David Skolnik]

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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.

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 (;-(

David Skolnik






>
>----- Original Message -----
>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
> > posted to the CAUT list because I suspected that there are some people who
> > are on there exclusively, remembering afterwards that I, myself have
> > sometimes found it confusing when the same thread subject is being carried
> > on simultaneously on both lists, sometimes with cross posting, and at 
> other
> > times on only one or the other.  I considered forwarding the CAUT 
> responses
> > to this list & visa versa, but suspect that will just make things worse,
> > so, for now, if you're interested, there are some other responses on the
> > other list as well.
> >
> > The piano in question is an old Steinway C (?) 85 note from about
> > 1883.  (There was either a recent posting or it was on someone's web site
> > that I saw an excellent listing of old models and dates.  I can't find it
> > at the moment).  The delamination between inner and outer rims goes
> > completely around the perimeter.  The visible gapping is generally from 1
> > to 2mm.  I only had a flat steel handled upright mute (.5mm or .020") to
> > use as a feeler gauge & it tended to insert between 1 to 2 inches 
> throughout.
> >
> > The piano was recently rebuilt (within the last year and a half).  There
> > have been significant tonal deficiencies, especially in the 5th and 6th
> > 8ve.  From the 7th rib up there is no apparent crown.  I didn't notice the
> > delamination when the piano first came back, but, in spite of a few months
> > out of the year of rather low humidity (20%), I doubt that such a 
> degree of
> > separation would have happened in such a short time.
> >
> > The main question for me is, what design parameters are impacted, and to
> > what degree, when there exists a significant amount of inner rim -outer 
> rim
> > separation of a unified rim design.
> >
> > At 09:35 AM 03/29/2002 -0800, Del wrote: (Edited)
> >
> > >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.
> >
> > >There is far less stress
> > >on piano rims than is commonly thought.
> >
> > What are the sources of stress in a single rim construction? The initial
> > bending creates the classic tension/compression stress.  Spreading the 
> arms
> > to fit the pinblock relaxes some of that stress, but stresses the cured
> > glue joints. Some stress is transferred from the strung plate. and perhaps
> > some outward stress from the compression of the soundboard.  Some of the
> > stress is internal, some imposed.  Would the acoustical properties of the
> > rim change over time, as the internal stress dissipates?
> >
> > >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.
> >
> > >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.
> >
> > So, what purpose does the outer rim serve, in a Steinway?  Would you
> > suspect any discernable difference between a Steinway built in the
> > traditional manner and one constructed with a 2 part rim?  For that 
> matter,
> > when did Steinway begin unified rim construction?
> >
> > >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.
> >
> > >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.
> >
> > In an older instrument such as the one I have described, I would assume
> > that most, if not all of the original internal tension has 
> relaxed.  Unless
> > the outer rim contributes to rigidity of the soundboard mounting, 
> affecting
> > crown and energy reflection,  the only reasons I can see addressing rim
> > separation would be either cosmetic, to prevent potential transient
> > vibrations, or to keep it from getting worse.  Have I misunderstood or
> > misstated your position, or does this correctly reflect your thoughts?
> >
> > Thanks -
> >
> > David Skolnik
> >
> >
> >

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