Official Luthiers Forum!

My shop is fully climate controlled but I still try and minimise time between bracing up a top and getting it attached to the sides. I usually get the top to brace up stage and then get the sides bent up and ready to take the top before starting bracing.

I don't think it matters as long as the humidity is stable in the shop.

Mark

I assume most hobby builders can't fully climate control things; I know I can't, and don't, but the RH around here is pretty much always in the right range for buidling (45 to 55%), at least in the rooms I keep my acoustic sets in. Still, I'd rather not risk things, and I don't suspect most first timers or hobby builders already have fully controlled shops.

Hesh,
Personally, I like to wait at least a week after bracing before I attach the
guitar to the rims. I can see absolutely no dowside to leaving the top
around for a while. And there isn't a good reason why you shouldn't
attach the top after the braces are on and the glue is fully cured.

However, I like to check the radius of my tops after about a week. The
top is so vital that I want to know everything is as it should be - and I feel
like waiting a week or two is good verification.

But the bottom-line is that it doesn't matter. And constant humidity
control should be a given in lutherie. A fluctuating environment is just
asking for structural problems. Everyone can maintain a small closet or
room where the guitar rests/resides during the construction and finish
process.

I'm in the "glue it up immediately after voicing" camp. It's a matter of consistency in building and trying to have control over as many variables as possible for me.

If I were running a factory, I might feel differently but my production runs are one at a time and as such are far easier to control. I guess it's just one more advantage that can differentiate a hand-built custom guitar from a factory model.

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JJ
Napa, CA
http://www.DonohueGuitars.com

I was told the exact thing you are proposing Hesh: if humidity is an issue at all, time your build processes to glue up the box as quickly as practical, and take steps to minimize humidity influences IF it's an issue. If the humidity isn't an issue, then the plate can stay out as long as needed for the regular build schedule.

In my latest build, the back and top (post bracing, and carving) laid around for several weeks and weren't out of line at all to the radius of the rimset when I did the brace fitting.

That said, I guess it makes sense in a production environment to brace/carve multiple plates at a time...so to some degree I would think they HAVE to sit around, some longer than others I suppose.

Bottom line: I'm with Blanchard.

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Eagles may soar, but weasels don't get sucked into jet engines.

Like JJ I try to glue it up as soon as possible. My instinct says that the top, which is trying to remain flat, will pull on the thin brace ends, possibly distorting the braces. One would think that once bent back to shape on a rim all would be good but there seems like a possibility of something wonky going on with the brace.

I have waited 3 or 4 weeks, but I keep the braced top and back in the radius dish under pressure.

The humidity in my shop yesterday was 43%, but it was 107 degrees. My work is currently on the dining room table.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

I have waited as much as 3 weeks to glue a top on a guitar, but the top was in my air conditioned shop during that time. I think the only time it would matter how soon you glue it up would be if it was not in a humidity controlled environment.

I have actually thought about gluing up several top sets and have them "rough" braced and waiting for future builds. It would be nice to have a radiused piece of oak to clamp the top to to hold it in place while it waits in line...

_________________
Reguards,

Ken H

A friend of mine is rebuilding an old Gibson Gospel & he's really taking his time about it. His braced & tuned top has been sitting in my dryroom for two months.
While I was out of town for three days SOMEONE left the dryroom door open & when I returned I found the humidity in the low 90s. My buddy's top looked about the shape of a Pringles...
I slowly brought the RH back to 45% over the following few days & the top returned to its former shape & has stayed that way for the past month.
Looks like we dodged the bullet, but it sure gives one an idea of how much stress can build up when an instrument is exposed to extremes in humidity.
I like to get the top & back glued to the sides within a few days of finishing the bracing... Once I'm sure the glue has fully dried.

I've got some tops around here that have been braced for months, waiting for the rims. (And, the rims are patiently waiting for them.) They are in fine shape...as long as the RH stays constant.
As far as the top distorting due to the tip end of braces being thin, it's not a problem (well, to me). Once the rims are pared down to the proper radius, the top is clamped onto those rims, and return--as needed--to proper form.
Put me in the Alfred E. Newman camp: "What, me worry?"

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

[QUOTE=Hesh1956]
So where this is leading in addition to the original question is should a top be under stress or not when attached?
[/QUOTE]

Hesh,

Just tell it that you are going to spread glue around it's edges, clamp it to a rimset, clamp another piece of wood on it, drill six holes in it and put it under 150-170lbs string tension.

That ought to stress it enough

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

We don't make a big deal out of it. I'd guess that we glue tops on within a couple of weeks of bracing them, but that's because of our normal production flow and how we batch parts.   We do keep our assembly room at about 48% and 72 degrees or so.

It's really not that hard to keep at least a portion of your shop at a reasonably controlled humidity level. Just make a closet out of Visqueen plastic or something and keep your parts in there when you're not actively working on them if you can't control the whole shop.   For doing the shop or a room, Sears has pretty good dehumidifiers for a few hundred bucks or you can add moisture with any number of humidifier options.   

I think that in a decent shop this is a non-issue.

As for stress...

What about the Larson brothers' proud claims, "Built under tension"?   Pretty wonderful instruments...well worth studying...and intentionally build with stress in them. Ditto Selmer/Macaferris. Ditto any guitars built with domed tops and/or backs.

Orville Gibson first built his archtops with carved backs and sides, not bent sides, reportedly because he didn't want the stress in there from bending.   Well, so much for that idea!   

Stringed instruments are a balancing act of stresses. If you want stress free, then take the strings off...

I glue my tops the day after I brace them. Years ago I built a guitar in a non environmentally controlled shop and the next day the top looked like a potato chip. That guitar taught me a valuable lesson about maintaining proper relative humidity levels. Even though now I maintain 38%-42% @ 72*F I just got in the habbit of gluing the next day.

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tim...
http://www.mcknightguitars.com

I don't understand the basic premise here. If a top is braced at too high a RH, gluing it to the rims, however fast you do it, is not going to fix anything. Once the top is glued to the rims it is restricted in it's movement even more than if it were only braced. If the top is braced at 70% RH, then the first time the central heat kicks on in winter I think you might have a problem if the top was glued to the rims after ten minutes or ten days. Maybe I am missing something, but I don't see how speed can make up for lack of humidity control.

                      Peace, Paul

Good point Paul.
I think this discussion assumed that the top was braced under controlled humidity conditions...
I know for a painful fact, that if you brace a top / back under high humidity conditions, then you give the guitar to a friend & then he decides to move to the frozen north... It's gonna make it back to your shop for a top replacement & the back is likely to have a lovely reverse arch to it.
(unless he keeps the guitar humidified, which he didn't)
This is the instrument that convinced me to build a 10' X 12' humidity controlled room in one corner of my shop.

    I have always left my braced tops sit in my shop for several weeks
before voicing them and then another few weeks before gluing to their
rim. All wood glues take more than a few days to dry to their full and final
hardness so the time has always made sense to me. Because of this cure
time, the braced top can show obvious differences in resonant frequency
and sustain after a week of drying so I allow it before I begin to remove
material from braces.

    Once the glue is fully hardened, the joints between the top or back and
their respective bracing parts can present what will be their final
transduction of individual tones to the tone of the system that they are a
part of. It's common knowledge that the braces serve multiple purposes,
especially on the top, to not only provide structural integrity, but also to
transport the vibration created by the strings from the bridge area to as
much of the plate as possible. The goal in calculating and arriving at the
exit points of the four legs of the "X" braces should at least include the
consideration of the location of the nodes or points in the plate's
vibration wave that exhibit an amplitude of zero.

   Every top that i brace is under tension or stress while free standing as is
every braced back. That stress contributes to the resonance of the plates
individually and then to the closed, bound body as a system. The effects
of both vibration and reflection can be dramatically enhanced with a little
tension. If you're arching your top or back at all, you are building under
stress, plain and simple. I love the Larson Bros. instruments and have
embraced more than one point of their building philosophy or mentality.

    When my tops and backs are fitted to the rim, they lay in place before
clamping and make full contact around the entire perimeter so there is no
stress at the glue joints at the rim themselves, but only in the relationship
between the braces and the plates. It's kind of a "selective stress" build
environment.

    A "stress free" build goes out the window once strings are pulled to
pitch on a guitar since the stress applied by them is distributed through
every component of the guitar.

   I keep my RH in the entire shop within a percentage point of 45% and
temp with a degree either way of 70 degrees so i've had tops sit there for
more than a year between bracing and gluing without any change in their
shape.

    To answer the original question, though.....If you're environment is
consistent, it's not an issue.

Regards,
Kevin Gallagher/Omega Guitars