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<DIV><FONT size=3>In a message dated 2/19/2006 4:36:49 P.M. Pacific Standa=
rd
Time, Erwinspiano writes:</FONT></DIV>
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<DIV><FONT size=3> Dave</FONT></DIV>
<DIV><FONT size=3> Yes pre-loading the board can give a definite i=
dea
about string load it will carry. By pre loadingwe can take the slack
out. Since the soundboard is a non linear spring it is going t=
o
become more resistant as resistance is applied, providing it's built stron=
gly
enough within reason. The whole idea of the pre- stressed meth=
od
of setting bearing is to compress the board in some uniform
way before bearing is set & before it is strung. =
Pre
stressing the boar takes place with the plate in place. By plac=
ing
wedges between the plate struts & the too tall bridge caps.
</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT size=3> One simply<FONT
style="BACKGROUND-COLOR: transparent" face=Arial
color=#000000> pounds the board down by hitting the b=
ridge
top with a fist & at the same time pushing wedges in under the str=
ut.
As the board compresses it becomes more resistant to pounding att some point=
it
the resitance feels like your merely pounding on a Gymn floor & the boar=
d
won't compress further without undue force & This is far enough &a=
mp;
usually about a 3mm or so drop in elevation. It is a tactile sense whi=
ch
develops after doing it a few times. After the boar=
d at
the main strut is wedged down, then the process is repeated on the next treb=
le
strut which nets approx. 2mm compression & then the last which net=
s
about 1mm. </FONT></FONT></DIV>
<DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000=
000
size=3> The last wedge is not forced down as less bearing is n=
eeded
here a slight bit of down force at the bottom of the tenor bridge =
;is
all that's needed.</FONT></DIV>
<DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000=
000><FONT
size=3> Compressing the board along the long bridge =
also
forces the bass bridge lower as well & if it has a cantalever I set bear=
ing
at zero which will net less than a half degree or less & or the res=
t
can be shimmed to whatever you wish. I usually string the entire tenor=
treble first, raise it to pitch & then calculate bearing on the bass
bridge.</FONT></DIV>
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<DIV><FONT size=3> Then a nickel is placed under each treble
aliquot. Draw a bearing string thru the agraffesor capo cut
a V notch in the bridge top until the string just touches front=
of
bridge & aliquot at the same time. These V's become the target
height of you final bridge height.</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT size=3> <FONT style="BACKGROUND-COLOR: transparent=
"
face=Arial color=#000000>The bridge needs a bit more rear ward slope cut=
into it
especially the top 2 treble segments but this is the general
idea.</FONT></FONT></DIV>
<DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000=
000
size=3> This method can also be fine tuned using adjustable plate
suspension systems allowing the sweet spot to be determined but usually it i=
sn't
necessary.</FONT></DIV>
<DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000=
000
size=2><FONT size=3> Dale</FONT></DIV>
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<DIV> </DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"=
><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000
size=2>Ron:<BR><BR>While you have an unstrung board is it possible to =
put
weights on the bridge approximating the downbearing load you expect to h=
ave
then reexamine the crown and bearing angles? <STRONG>Would this gi=
ve
an elementary idea of the board's ability to sustain that
load?</STRONG><BR><BR>dp<BR><BR>David M.
Porritt<BR>dporritt@smu.edu</FONT></BLOCKQUOTE></FONT></BLOCKQUOTE>
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