R,C&S question JD

[Richard Brekne]

Hi JD

Your understanding of the RC & S board seems pretty solid to me. One 
point I'm less sure on is the amount of compression in the panel after 
the strings are on. The ribs are more solid as you say... and short ribs 
with tight radii are not all that easy to bend.  Yet there is a stated 
goal of applying enough downbearing so that 25 % of the unloaded crown 
remains after stringing. That strikes me as equating to a good deal of 
compression in the panel. Looking around these past few days and asking 
questions in a variety of places... I'm left wondering if there IS any 
direct way of figuring just how much compression a given lateral load on 
a beam will build up in the panel. Perhaps its a matter of looking 
around long enough... perhaps it just hasn't been considered directly 
much for the same reasons that tension along the grain of beams doesn't 
seem to attract too much attention in wood engineering texts.

As far as piano tone --- opinion --- and objectivity.  Admittedly there 
seems to be some degree of objectivity involved. But one can not escape 
the observation that musicians and listeners alike seem to draw delight 
from a far larger pool of sounds then what we as piano techs seem to 
define as good tone ourselves. One need only take consideration to the 
false beat phenomenon to see this. In my experience there exists at the 
very least a very large minority... if not an outright majority of 
people who prefer the lively sound of an instrument with lots of .... 
shall we say "vibrato" present. I hear quite often negative comments 
about pianos bereft of false beats as being dry and harsh sounding... 
regardless of how you voice them.  Others of course feel completely 
different on this same matter.  I have a real curious example just the 
other day.  A fellow who is an accordian player by profession... sourest 
tuned accordian you could ask for as well... yet he is sooooo hung up in 
piano bass string clarity. Way beyond what any set of bass strings can 
offer. Go figure where that combination comes from ?

We may have some quantifiables to be sure... but it strikes me as pretty 
clear pianists enjoy a far greater range of sounds then we piano 
technicians seem to allow for.

Cheers
RicB


    As I understand it the RC&S board is subjected on glue-up to a
    greater tensile force on the unribbed surface but (a) since it has
    been less dehydrated and (b) because it has been forced round a
    tighter radius against much less flexible ribs, some of this tension
    will either remain or be reduced to a point while the assembly is
    free.  Compression at the glue line will exist, of course.  Once the
    piano is strung, the downbearing will press down the soundboard less,
    because the beams (ribs) are more solid, and hence there will be less
    reduction in the curvature and less increase in compression (or
    decrease in tension) at the surface of the board.  Now those who
    practice this art will be able to give actual rough values to these
    phenomena, but this method of construction seems to have as one of
    its aims the avoidance of anything close to the degree of compression
    to which a high-class traditional board is subjected.  The
    specialists will correct me if I am wrong.

    As you say, a lot of things are unclear, and these discussions often
    start off with some hope of providing enlightenment, facts and
    figures, and a statement of principles but all too often, almost
    always, deteriorate into a rather vague mish-mash, a bit of dogma and
    bye-bye.  I try to limit myself to facts and experience and as much
    science as I can muster, which is not always much!  Opinion is
    worthless -- and in my view excellent piano tone is far less a matter
    of taste and opinion than you have recently suggested.  There are a
    number of measurable qualities in the sound of a good piano.  It's
    nice to have a fairly good string scale but I could name several
    pianos that won gold medal after gold medal in the old days with
    quite outrageous stringing scales and took the prizes because the
    work they did on the belly was good.  The belly itself produces
    nothing, but what it does with what it's given is what makes the
    difference between a "satisfactory" piano and something that sends
    shivers up your spine.

    JD