Fix what's not broke?

[JIMRPT@AOL.COM]

In a message dated 3/21/2001 5:10:30 PM, Richard B. wrote:

<<"Is is the pressure of strings
themselves that will sooner or later "crush" the board... or is it the year in
year out changes due to seasons that does em in... or what.">>

Yes. :-)

 Actually I hope the 'Sages a deaux' jump in here cause they are more 
technically minded and mo knowledgabler than I.

 There is a 'natural' balance in all structures and within that balance there 
is a range of capabilities. Should a 'balanced' structure never be pushed 
beyond its inherent capabilities there is no reason for that structure to 
fail. For instance if a soundboard is produced with 10% emc (illustration 
purposes only) and rib crowned with ribs also at 10% emc then there is a 
natural range wherein this assembly will operate perfectly well and provide 
long service without any structural deformity/damage.  However should this 
structure be pushed beyond its capability, in either direction, then damage 
of some type will begin to occur.
Dry it out too much and it will split/separate/flatten...Add too much 
moisture and it will develop pressure ridges, tear away from the ribs, crush 
wood cells, etc.
 
 Now if we take that balanced structure (soundboard) and restrain it in some 
manner........... we alter the balance of that structure.  Let's say we glue 
it in the rim of a grand. By doing so we alter, or limit, the 'usable' range 
of any balance within that board...........and for the sake of discussion 
let's say that we now have 30% of the 'balanced' range to work 
with...............as long as what we do does not demand more than that 
remaining 30% of capability then the board will not suffer any deformity or 
damage.  But now we put in bridges and a download from the strings
which produce forces of their own.........still if we don't exceed that 
remaining 30% capability of the board then there will be no structural damage 
and for all practical purposes you will have a balanced structure in-toto.

 The remaining 30% of original capability has now become for all practical 
purposes 100% of the capability of that board.  So the question is what will 
cause damage to the board at this point? Right?

 The answer is 'anything' that exceeds the capability of the structure to 
withstand pressures without 'any' damage to 'any' of the celluar sructure 
within.
Different board fabrication techniques will provide different parameters of 
"remaining" capability for us to work with. Probably a rib crowned board will 
give us the largest percentage of 'residual' capability to fool around with 
and a compression crowned board will give us the least.

 So the real answer to your original question is.......... Yes. :-)
My thoughts.
Jim Bryant (FL)