Hello Mr. Collado:
The Purpose of gluing on all the braces on the soundboard at once is that it
is easier then to control some very important factors.
First, one wants to have the top normalized in a controlled environment
with respect to humidity. The humidity in the box should be on the low side
of of what you expect for the instrument to find most often . This
normalization is to have the top in such a place for around 5 hours or more
so that you know the top has been "stabilized" in sofar as its internal
moisture is concerned.
A go bar box as mentioned in earlier posts with foamcore surrounding it on
all sides is also what I use.
You want to work fast because when you open the box front up in order to
glue and place the braces, the relative humidity will change in the box as a
result of outside humidity being higher (or lower as the case may be) as
well as as result of the presence of the water in the glue itself.
One then seals the box as soon as possible so as to keep the relative
humidity constant inside... you will want to check this from time to
time...
If you glue down several braces but not all, and want to come back to the
project at a later date, you will have to once again stabilize the top to
the EXACT humidity you used in gluing on the previous braces for 4 or 5
hours or so before continuing.. This is to say that you will want to be
within a percent or so. This is actually a pain to do, so its better to
brace the entire top at one go.
Also if the top is only partially braced say at 35 percent and is left open
in the shop even 5 or 6 percent higher or lower for any period of time, the
top may well take a set and bow in one way or another creating a potato chip
issue.. This is a REAL pain to flatten out.
Secondly, the reason for exact humidity here is that apart from trying to
prevent the top from cracking by bracing it in a slightly lower humidity
than expected for the instrument, you are most importantly bracing the top
with an eye (or better said 'ear') to an even dispersal of moisture interior
to top, which translates to an even width across the entire top as it is
being braced . This will result in a completely relaxed top with NO built in
stresses as would occur if you were to apply say several braces at 35
percent, and others at 40 percent humidity at different periods of time.
In this example where the humidity was at 35 percent , those braces applied
will fix the width of the top to be slightly less than those sections
braced where the humidity was in the 40 percent range because with more
moisture in the wood the top will want to expand in width in this section,
and braces put on in the 40 percent range will fix the top at this expanded
width.
This 5 percent differential across the top(our example) will create
lateral tensions in the top which will adversely affect the sound this
especially in the "tail" of the notes , which after all is where the
mystery of the lute sound pretty much resides.
What happens is that as the harmonics imparted to the top from the pluck of
the string decays after a period of time , the energy the harmonics create
begins to lessen to the degree that it will approach the level of energy
embedded in top by the built in stresses .. At this point the stresses will
begin to dominate and restrict the top from vibrating in accordance with the
harmonics as created by the pluck. The tail of the note will hit a point in
its decay and then seem to deaden in complexity, and then die altogether .
In general, instruments made in this way (classical/flamenco guitars too)
will tend to want only new strings - as older ones REALLY emphasize this
deadening effect of a badly braced top.
best
r
----- Original Message -----
From: "Santiago Ramos-Collado" <[email protected]>
To: <[email protected]>; <[email protected]>
Cc: <[email protected]>
Sent: Wednesday, December 02, 2009 9:56 AM
Subject: [LUTE-BUILDER] Re: hide glue gram strength
Greetings to all.
I'm missing something here. What's the use of gluing all the braces at
once?
Best regards,
S. Ramos Collado
--- El mie 2-dic-09, [email protected]
<[email protected]> escribio:
De: [email protected] <[email protected]>
Asunto: [LUTE-BUILDER] Re: hide glue gram strength
A: [email protected]
Cc: [email protected]
Fecha: miercoles, 2 diciembre, 2009, 12:53 pm
Chad,
Well, it's a small anvil. About a foot long. A blacksmith's anvil
would definitely be overkill. I haven't actually glued on all of the
braces at one go yet, but I think I may try it on the next instrument I
build. It does sound like a bit of a circus act, though.
Re-gluing bridges (which, unfortunately, I've gotten some practice at)
is about the one thing that I do use go-bars for. I have a jig (I
think jigs outnumber power tools in my little shop) to hold the lute
horizontal and I slide it under the wall cabinets over my work bench.
Then I have little go-bars I made from strips of beech that are sized
to fit the center and the wings of a bridge. So the cabinets act as
the roof of a go-bar box, if this makes any sense. Once I've done the
gluing I slide the lute in the jig under the cabinets and stick the
go-bars between the bottom of the cabinets and the bridge.
Before gluing on the bridge I attempt to extend the working time of the
glue as much as possible by pre-warming the bridge and the bridge
location on the soundboard with an electric heating pad for about an
hour. The younger posters on this listserv may not have a heating pad
around the house, but by the time you're in your 50s you will.
I only have time to build instruments in the winter, when my basement
gets rather cold. So I've made an enclosure out of foam core for the
go-bar box (that never gets used for go-bars) and put in an electric
light to pre-warm braces and the soundboard. I assemble the box at
least a day ahead of when I'll start gluing, turn the light on inside
with the parts to be glued, and leave it that way for several days
while I'm gluing things together. The glue pot is next to the
enclosure and all of the gluing happens in the box. It also serves to
dry out the wood if there is any residual moisture. Part of the fun
for an amateur is figuring all this stuff out.
Tim
--- [1][email protected] wrote:
From: "Chadwick Neal" <[2][email protected]>
To: <[3][email protected]>
Subject: [LUTE-BUILDER] Re: hide glue gram strength
Date: Wed, 2 Dec 2009 09:49:09 -0500
Hi All,
Thanks for weighing in on this topic. I've been using 315, and I think
I'm
ready to order some lower strength. It's been good to use especially
when
you want the fast tack and I've adapted my technique to suit. I would
never
be able to use Tim's method of glueing the braces all in one go and put
a
board over top with weight. An anvil, Tim??? Wow certainly not a
blacksmith's I'm assuming :-))
No, It has a fast gel and even by the time I get the go bars on one it
has
begun to gel, one more bar and I can clean squeeze out from the first.
For bridges, I like it both in construction and repair, especially the
repair, when you have to hold the bridge by hand for several minutes. A
good
thinnish water ratio and it will hold fast. I have a really hard time
waiting the full five minutes, perhaps, too much coffee in me. I
usually
fidget around after a couple minutes.
I have veneered and all of the other operations, but you have to be
fast!! I
also like it for rib gluing, it's quick.
Shrinkage though, I witnessed a old jar with a thin layer of dried glue
crack a baby bottle!
Chad Neal
-----Original Message-----
From: [4][email protected]
[mailto:[5][email protected]] On Behalf
Of Andrew Hartig
Sent: Tuesday, December 01, 2009 4:46 PM
To: [6][email protected]
Subject: [LUTE-BUILDER] hide glue gram strength
I'm wondering what gram strength glue other builders out there are
using. I noticed recently that while a local luthier supply
(lmii.com)
sells 192 gram strength "high clarity" (it really does have high
transparency) hide glue as their standard for lutherie, another
general
woodworking company (toolsforworkingwood.com) markets 3 types: 192,
251, and 315 (only the 192 comes with a "high clarity" alternative).
The only thing that really got my attention here was their
description
of the strengths, copied below:
* The 192 gram strength is a good general purpose glue, and it's
the
least expensive hide glue around. That's why it's the most
common.
Its real application is veneering, although you can use it for
regular gluing in a pinch. A lot of people consider it the best
all-around glue for general woodworking (including veneering),
because it also has the longest open time. If you are new to
hide
glue, this is the grade you should get.
* The 251 gram strength glue is traditionally the most appropriate
for regular cabinetwork. Its higher strength means that you can
do
rub joints more easily, and clamped joints will have less time
to
creep. But it's not optimal for veneering, when you'd want the
maximal amount of time for squeezing out the excess glue.
* The 192 gram strength "high clarity" is more expensive than its
cousins because it is especially refined for maximum
transparency.
It's a good all-around glue that's slightly more tacky then the
regular 192 glue. This is the glue to use if you are worried
about
visible glue lines.
* The 315 gram strength is a special purpose glue for very high
stress applications. It is favored primarily by instrument
makers
for situations where a joint will be under constant force. Of
the
glues the 315 has the shortest open time.
So, is 192 not strong enough for lutherie, as implied by the
description of the 315? Or is the concern here more about
high-tension
modern instruments?
What are others using?
(As an aside, I should mention that I've had no troubles so far with
using the high clarity 192.)
Curiously,
Andrew
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