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<DIV>> One piece of the explanations for the observed effect of the
multi-species <BR>> laminations doesn't make sense to me, and I wanted to run
it by you all.<BR>> <BR>> Regarding Michael's experiment, ie, three
identical pianos with three different <BR>> bridges, 1-solid maple,2-maple
with mahogany laminations, and 3-maple with <BR>> mahogany and ebony
laminations... <BR>> <BR>> The explanations for the observed effects all
seem to point to the effect of <BR>> increased density/mass.<BR>> <BR>>
Here's my question. In the 2nd piano example, maple and mahogany laminations:
<BR>> since the specific gravity of mahogany (swietenia macrophylla= .51) is
actually <BR>> less than that of maple (.63), this bridge is actually less
dense than the stand <BR>> alone maple, assuming absolute density is what we
are looking at.<BR> <BR><FONT color=#0000ff>The specific gravity of the
wood is higher in the maple, or at lease we are assuming that this "specific
piece" of maple has a higher specific gravity than the maple/mah, but the
overall weight of the mah/maple laminated bridge is more; there has to be a
reason for this. After thinking about Ron's question about weight, I
weighed the 3. The solid maple comes in at 3.5 lbs, the mah/maple 4.0, and
the ebony/mah/maple at 4.5. Don't ask me why! Maybe Terry used lead
based epoxy in the maple/mahogany laminated bridge :) The maple/mah laminated
bridge may have maple which is a higher specific gravity than the maple of the
solid bridge. The solid bridge looks to have much wider grain than the
beatufiul maple Terry used in the laminated bridge. I don't know what the
mahagony in the laminated bridge is, Terry was the head chef on
that.</FONT><BR></DIV>
<DIV><FONT face=Verdana size=3>If the volumes of the three samples is the same,
I see no good reason that the solid maple would be lighter than the
mahogany/maple sample. It is obvious from handling the wood that the mahogany is
much less dense than the hard maple. Obviously, your statement: "<FONT
face=Tahoma color=#0000ff size=2>The maple/mah laminated bridge may have maple
which is a higher specific gravity than the maple of the solid bridge.</FONT>"
is true, but why? Can I assume the solid maple sample did not
originate from my shop? Is there any chance the solid maple sample is soft
maple? That's about the only explanation I can think of.</FONT></DIV>
<DIV><FONT face=Verdana size=3></FONT> </DIV>
<DIV><FONT face=Verdana size=3>It doesn't surprise me that the
mahogany/maple/ebony assembly is more dense than the other two - that ebony is
extremely dense - small pieces of it weigh a bundle. I used a two-part
urea-formaldehyde resin adhesive for both the mahogany/maple bridges and the
mahogany/maple/ebony bridges.</FONT></DIV>
<DIV><BR>> To my mind, this doesn't jive with the straight-up absolute
density <BR>> explanations...unless... the effect of increased density occurs
as much from the <BR>> layers of non-uniform densities introduced by layering
different species (with <BR>> differing densities), as from the <BR>>
actual absolute densities of the woods. <BR> <BR><FONT
color=#0000ff>There's MUCH more I don't know about this than what I do
know. Part of the intruige for me in this thread has been the subject of
mass loading which has been touched on. Between that and Ron's comment
about the "magic vibrations theory", it is challenging most of what I
thought I understood about what's "really going on in that there belly". My
initial thinking is that a vertically laminated bridge is more efficient than a
solid bridge. </FONT></DIV>
<DIV><FONT color=#0000ff></FONT> </DIV>
<DIV><FONT face=Verdana size=3>I think that could be applicable if you
believe that sound propagation along the length of the bridge has a significant
influence on sound ultimately eminating from the soundboard. If one subscribes
to the theory of strings vibrating the bridge, which vibrates the soundboard,
which moves air, then perhaps there is not likely not much difference between a
solid and laminated bridge. The biggest reason I like a laminated bridge
root is because it should never crack.</FONT></DIV>
<DIV><FONT color=#0000ff></FONT> </DIV>
<DIV><FONT color=#0000ff>But there's no question that the mass has to play into
this. Back to the extremes, I seriously doubt that a laminated bridge made
with balsa could compete with a solid maple
bridge. </FONT><BR> <BR><FONT face=Verdana size=3>As you state,
you would have mass issues with a balsa bridge root. But you might find the
balsa is so soft that it imparts a damping effect between string vibration and
soundboard movement. Might not want to spend too much time experimenting with
balsa. </FONT></DIV>
<DIV><FONT face=Verdana size=3></FONT> </DIV>
<DIV><FONT face=Verdana size=3>However, if you are a paying customer and want me
to build you one........ ;-)</FONT></DIV>
<DIV><FONT face=Verdana size=3></FONT> </DIV>
<DIV><FONT face=Verdana size=3>Terry Farrell</FONT></DIV>
<DIV><BR><BR>> Does this make any sense?<BR>> <BR>> Jim I<BR>>
<BR>> <BR><BR><BR></DIV>
<DIV>
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