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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=sec@overspianos.com.au =
href="mailto:sec@overspianos.com.au">Ron
Overs</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=davidlovepianos@earthlink.net
=
href="mailto:davidlovepianos@earthlink.net">davidlovepianos@earthlink.n=
et</A>
; <A title=pianotech@ptg.org =
href="mailto:pianotech@ptg.org">Pianotech</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> May 08, 2003 7:40 =
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Making =
bridges</DIV>
<DIV><BR></DIV>
<BLOCKQUOTE cite="" type="cite">What's a scarf joint?<BR><BR>David =
Love</BLOCKQUOTE>
<BLOCKQUOTE cite="" type="cite"><A
=
href="mailto:davidlovepianos@earthlink.net">davidlovepianos@earthlink.n=
et</A></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>A scarf joint is a variation on a butt joint, which instead of =
being
vertical, is leaned over at an angle to present a longer and stronger =
gluing
surface between the pieces being glued. A good scarf joint can be
approximately 90% of the strength of the wood. We use Titebond Extend =
for all
scarfs since it has a tensile strength of around 3,600 psi.</DIV>
<DIV><BR></DIV>
<DIV>However, a standard scarf joint will result in the two pieces =
being in a
line, which is not satisfactory for the manufacture of a bridge. The =
joint
required for bridge manufacture is the compound scarf joint, which has =
the
standard angled scarf joint<FONT color=#0000ff> (typically angled at =
a slope
of 1 in 5)</FONT> with an added angle to cause the two pieces to be =
joined at
an angle. This is necessary to allow all of the bridge stock to follow =
the
outline of the bridge. Once all scarfs are joined<FONT =
color=#0000ff> (usually
there are two per long bridge)</FONT>, the bridge outer profiles are =
then cut
out with the band saw.</DIV></BLOCKQUOTE>
<DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#000080 size=2>Ah, Ron, we can tell =
you're not a
wooden boat builder! A good scarf joint will equal the strength of a =
solid wood
beam. And it will have a slope of 1:8 (non-structural use) or 1:12 =
(structural
use). The amount of slope also varies with the glueability of the =
wood
being joined. Spruce bonds very easily, maple somewhat less so. =
Finger-joints,
by the way, are simply a form of scarf-joint. In this case the scarfs =
are made
short and are stacked for less wood waste.</FONT></DIV>
<DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#000080 size=2>We can compromise on the =
slope of the
scarf in the construction of piano bridges because it is a =
"non-structural"
application. The absolute beam strength is not critical. </FONT></DIV>
<DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#000080 =
size=2>Del</FONT></DIV></BODY></HTML>