Cracks and ridges

[Brent.Fischer@asu.edu]

Dear Mr. Hartman,

You're sure right, the alleged article was far too commercial. However,
I support Vince's decision to print it despite your concerns.
After reading Chapter 6 several times ( being academically
challenged - it's necessary for comprehension )  I will surely adhere
to Hoadley's "1% compression limit rule," although he does go on to
say it is only a rough approximation, which you also mentioned.  Del
Frandrich says the soundboard as a "spring"  will be stronger only
up to the point of fiber crushing, which for my process means I am as
close to edge as I can calculate. The reality is that compression is a
given to achieve tonal power.  Procedures for maximizing the amount
the wood is willing to give, and minimizing the cell damage that occurs,
are of great concern to me especially the long-term effects of compression
set. Hoadley says that moisture cycling will have more effect than
mechanical stressing. Perhaps more attention should be paid to
controlling the piano's environment. You have expressed the importance of
quarter-sawn accuarcy to help control fiber crushing, but how much of
the supply would be left if this were a universal criteria?  I do
applaud your determination to build a better board and I agree there
should be a consensus on improving techniques to minimize the problems
which you say need careful study.

Tonal demise and structural failures have just not been common or evident
to me in the huge number of Steinways I have serviced over the years with
compression ridges past the "1% rule" or even a little further than the
parameters you have suggested. The length of seasoning is an issue I
couldn't agree more with,and I have found that by seasoning a crowned board
by as much as 3 to 6 months before installation the compression effects
stay within an acceptable range. But how is it possible to determine
the minimum amount of time it takes an assembly to reach relative
equilibrium?

The use of hide glue for controling tension in the joint is new to me.
I do use Pianotek's high gram strengh hide glue in rib and bridge gluing
because the extreme brittleness and hardness of this glue after curing
may contribute to board stiffness and acoustical properties. Am I wrong?
The differences in Eastern and Sitka spruce have had mixed results
in my work. While the bass and mid-range have had darker tone qualities
with Eastern spruce, several instruments have also had plenty of treble
brightness and power.

Treble bridge crown and the effect it has on an assembly is a related
issue which I feel deserves investigation.  Have you ever placed a new
and an old Steinway bridge on a flat surface and measured the difference?
The new one will be have twice the crown suggesting the tension along
the grain is higher when the board is newer.  I am unsure exactly how
this effects the compression grain under normal loads.

The longevity or expected life of a soundboard should have an approximate
range of which I have no knowledge as to an established criteria. For
performance pianos, it is my belief that after around ten years it is
time to extract the wet noodle and install a freshly compressed transducer.
Perhaps for the non-performance piano, we should look to a life span of
about thirty to fourty years.

Even in the 1920's, Steinway dealt with the ridge issue at a time
when the quality of wood selected for use was at its' best.  Would a
decrease in compression to eliminate raised grain be worth the
sacrifice in tonal qualities ?  Personally, I think the greater
chance of losing these qualities far out weighs living with ridges.

Thanks for listening and I have appreciated your enlightening
observations. Brent


Brent.Fischer@ASU.EDU
Arizona State University/Tempe