high humidity (was tapping strings)

[Richard Brekne]

Fred Sturm wrote:

> For my part, I am pretty well convinced that soundboard
> movement/swelling is the major dimensional change affecting tuning.
> Large area, hygroscopically active wood, constrained around the rim. A
> small dimensional change gets magnified by the rim constraint to
> generate a large push upward (assuming crown). Cross sectional swelling
> by the bridge comes nowhere close. (Take an 8 1/2 x 11 sheet of paper.
> Hold down one end and push the other 1/4" toward the constrained end.
> Watch how high the middle goes up. You'll be amazed.)

Course there is one easy observation that creates a bit of a problem for that
view.... Why then does the section of strings just below the treble break, and
that just above behave in such a disjunct fashion then... ? You need to explain
this. Then too... Ron can run some rather seductive numbers at you that seem to
point in a different direction. Thirdly there is, if I am not mistaken, some
measure of discussion as to degree of the validity  of the rim constraint effect
you site.

Seems to me that the question hasnt really had a fully satisfactory answer yet.

>
>         But it's very complex, as the push upward is countered by various
> twisting pressures exerted by strings (especially considering variations
> in waste lengths toward the hitch pins). How pitch is affected is partly
> determined by relative tensions (if you want some of my take on why the
> tenor area is often affected the most, go back about 8 years or so in
> the PTJ to a series of letters back and forth).

Interesting that you use the term "waste lengths"...  just what specifically do
you mean by this and why are these <<wastefull>> (Semantics ??)

>
> Fred Sturm
> University of New Mexico
>
> Michael Jorgensen wrote:
> >
> > Ron,
> >     If the bridge were most of the cause,  why does the low tenor go so far
> > sharp?  It seems to me that if the bridge uniformly grew taller, the
> > shorter/higher strings should change most?
> > -Mike




--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html