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Bracing to light?
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Author:  arvey [ Mon Jan 29, 2007 12:25 pm ]
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I have a guitar that has come back to me after being out on tour for 2 years. It was looked at down in Toronto at the 12th Fret and they told the artist that it was to lightly braced for her playing style but I question if playing style should make a diference in how well the guitar stands up. She always uses lights which is what this guitar was built for. This guitar has been severely dried out a couple of times, the first time it came back with the fret ends needing filing I discovered she was on tour and wasn't using a humidifier as I had instructed,and the humidity in her house was down around 20%. When she is on tour she might go from playing in L.A. one night to Texas another night and then off to Europe for a month a few days latter. And in the winter of course the guitar is going from one plane to another. In A Calton case but still. Any way after filing the fret ends down that first time and instructing her in proper care It came back again last spring with the fret ends needing filing and the bridge pulling off. It was also showing signs of the top Bellying behind the Bridge and dropping between the bridge and the soundhole. Well It is back in again and their is a bit more bellying than would be expected behind the bridge but between the bridge and the sound hole the top has really dropped. You can actually see the drop starting at the finger brace (it's held it's shape at the brace but dips both sides). When you put a straight edge acoross the body in front of the bridge by the sound hole instead of being domed (24'dome) it actually drops a couple of cm below the level of the edges. The Bridge is actually slanted with a dome behind it and a concave drop in front. My questions, could this be caused by simply to light of bracing (I braced like all the others and I've built 15 of this model)or would this be a combination of light bracing and humidity or could it be simply humidity problems or something else. The other question is how do I fix this? Should I rebrace the top heavier and can I do this somehow without taking it apart/. I was thinking of Adding a brace at the back edge of the Bridge plate between the X braces and or possibly a brace in front of the bridge. Any suggestions on repair and possible causes would be appreciated. If this is due to too light of bracing it is a warranty issue but otherwise it isn't.
Author:  arvey [ Mon Jan 29, 2007 12:30 pm ]
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I should mention that when it was returned this time the humidifier was in the guitar but it was empty and the humidity in the guitar case was at 27%. The fret ends again need filing down as they are sticking out.
Author:  crazymanmichael [ Mon Jan 29, 2007 12:34 pm ]
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if the top dropped a couple of cm then there is something majorly wrong with the construction.

did you mean mm?????
Author:  LarryH [ Mon Jan 29, 2007 12:41 pm ]
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Richard,

It seems to me the only way to tell if humidity had a hand is to try and reintroduce some moisture back into the guitar. I saw a great video on a technique and the changes made to a very dried out Taylor over on their web site. Can't seem to locate it now. But is was VERY dramatic. The dome returned, the cracks disappeared and guitar basically came back to life.

Either way it would take a week but then you would know the culprit and either brace heavier if it seems that's the cause or insist that the humidity be kept up or the warranty is not valid. I'm very interested in the outcome.
Author:  arvey [ Mon Jan 29, 2007 3:21 pm ]
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Yes Michael I mean mm. So how do you beef up the bracing without having to disassemble (remove back or Top)?
Author:  crazymanmichael [ Mon Jan 29, 2007 3:58 pm ]
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2 mm is nothing like 2 cm, but still is significant.

have you inspected to ensure that the x brace joint is intact, that it's still glued to the top and not cracked, as well as the other braces..

what are the brace dimensions, and in particular the x? was the x capped? top thickness?

have you checked the moisture level of the instrument or do you plan to? i record the instuments weight when it is completed and can determine if it has beem allowed to go drastically one way or the other.

this almost sounds as though it is too wet, not too dry.

what is the action like. what is the saddle like compared to new?

what is the neck set like?

from the comments you make, i don't think you will be able to definitively isolate a single cause. the best outcome would probably be your being able to stabilize the instrument whilst restoring the playability/tone etc. that made the client select you in the first place at a reasonable cost in time and resources.
Author:  arvey [ Mon Jan 29, 2007 5:02 pm ]
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It isn't that it has moved only 2 mm, It has dropped a lot more than that. It has gone from being in a 24' arch or domed top to being around 2 mm the other way, in other words the arch has actually reversed. The bellying behind the bridge, as I look at it isn't much more than usual it is just that it is still arched up and the rest of the top has caved in. As far as details go, All the braces still seem good and intact, you can actually see the slight rise in the top where the braces are, and the drop to where there are no braces. The X is capped ( wouldn't build any other way, Top and bracing are Red Spruce, Braces are .25" X .625" and the Top was recorded at .11" but probably after final sanding is more like .1" I have done many tops thinner than this without problems. It is a 14 fret L-00 with a 25.4" scale. As far as measuring the humidity I haven't weighed the instrument before so can't compare, When it came in I put a Hygrometer in the Guitar and closed the case, it registered 27% humidity. The fact that the fret ends are sticking out a bit even though they have been filed down twice before when the guitar was dried out suggests to me too low of humidity. The bellying that I mentioned seems to have been from the string tension as it has gone back to normal with the tension off, perhaps a little light on the bracing there??? Mind you, all my guitars belly a bit when under string tension and this one isn't much ore than ussual, just looks like a lot more because everything in front of that has dropped so much. How do you see to much humidity causing the top to cave in? Normally my experience has been that high humidity causes a top to rise but this one is now concave from the bridge forward. If I am going to beef up the bracing how would I go about doing that? This guitar is, as I said played heavily by a seriously touring musician and she plays it hard, usually playing with a full band although she is doing more unplugged sets these days. I need to make sure this guitar can take the rigors of touring and the conditions that come with that. I suspect that I can't expect her to watch the humidity as much as I would like as sometimes when she is flying the guitar might be in transit all day.arvey39112.051712963
Author:  Steve Saville [ Mon Jan 29, 2007 5:57 pm ]
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It sounds like not only did it have poor humidity control, but it also may have had some excess heat. I suspect the excess heat is why the bridge is slanted with a dome behind it and a concave drop in front. I saw this happen to a Martin D-15 this summer. There is no way that guitar was under braced.
Author:  Dave White [ Mon Jan 29, 2007 8:51 pm ]
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Richard,

Lots of good advice here from others. Like you I find the "too lightly built for her playing style" phrase interesting. To me this means things like using a heavy attack and strumming style that overdrives the guitar too much, or liking a stiffer response of the strings. If the guitar is played with the light strings for which it was designed, then no amount of any playing style is going to cause bracing issues (unless there is massive amounts of percussive playing on the body or regular tuning up to Open E or Open A ). Now putting on heavier gauge strings to better suit a playing style would do something.

If they had said "too lightly built for her playing lifestyle" then that may be a different issue. On the road in rapidly changing humidity and temperature environments that swing from 20% to 80% in short time and little to no humidity control process would put some stress on the instrument. That's why lots of performers use workhorses like Takamine's on tour and hand-built guitars in private or for more intimate performances.

I suspect the guitar top has been doming in and out with the big humidity swings and as Steve says could well have been subjected to high temperature at some stage. Is there any evidence of glue creep on the braces on the top? Rapid swings of that range of humidity on a regular basis would certainly explain a lifting bridge.

I think the advice to rehydrate and stabalise the instrument first is good and see how it looks and plays in this state. The Taylor video Larry refers to is Here - Understanding Humidity.

A lot depends on your personal relationship with the player. Most handbuilders tend to be on the masochistic side of saintliness when it comes things that go wrong and blame themselves. From the sound of it you have more than enough evidence to support this as a non-warranty issue imho. The trouble is, if it is the environment the guitar is being used in that is the issue then you could go ahead and fix/retop or whatever and you will be back in the same situation a year or so down the line. If you go for safety and way overbrace then she will have a workhorse guitar but will have lost all of the magic that drew her to your guitar in the first place.

Hope it works out OK.Dave White39112.2052199074
Author:  crazymanmichael [ Tue Jan 30, 2007 1:11 am ]
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the reason i said it may have got too wet; yes the top will rise when humidity is too high, and it seldom returns all the way to "normal" after it is dried out. the string tension seems to allow a new "set" to take place. but if it is then allowed to dry too much, the belly will tend to remain and the area in front of the bridge up to the sound hole, not being held up by the strings, can dip as you describe as it loses moisture and shrinks.

they can tell mixed stories.

whilst the need to use humidifiers is fairly commonly known, the need to use desicant packs in humid climates is not as widely known.

i recall an old wood and steel article relating how an instrument sent back to taylor for repair lost about a pound of water in a drying cabinet between the time it arrived and they were ready to begin work on it. the humidity battle goes both ways and some owners just haven't the heart to fight it. perhaps we should encourage them to use one of the carbon fiber creations out there.
Author:  arvey [ Tue Jan 30, 2007 3:36 am ]
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At the present time I have the strings off and am rehumidifying it. I do have a lot of guitars come in needing to be rehumidified (during the winter with forced hot air humidity in a home is under 20% around here) and what I ussually do is put a plannet waves humidifier in the guitar inside the case to bring it back up. I can already see the shape returning to it. The issue will be how do I ensure we can maintain this.
Author:  fryovanni [ Tue Jan 30, 2007 3:44 am ]
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Would an instrument that is going to see rapid changes in humidity like this benifit from applying a film finish to all surfaces(inside the box as well as out)? I know that any finish will only slow the transfer of moisture, and if it is subjected to higher or lower humidity for an extended period it will take or release to equalibrium. Maybe it could knock the edge off the real quick radical changes. Actually I don't even know if you have done this already. So my question may be irrelevant.

Peace,Rich
Author:  tippie53 [ Tue Jan 30, 2007 4:19 am ]
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    I have another point of view to offer, you didn't say what size bridge plate you used. If the plate is too narrow you lose alot of rotaional support.
    While light bracing can really open a guitar , the lighter you brace the deformation can occur. Also what glues did you use. Heat can allow some glues to creep , thus the support of hide glues. the lightest bracing I use a .250" wide by .570 " high. The shape also influeces the stiffness so experiment with profile shapes to make thinks lighter yet stronger
   you often learn more from a failure than a success
john hall
Author:  arvey [ Tue Jan 30, 2007 5:13 am ]
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I always use hide glue which is what I used for this. Bridge plate was the same size as I have used on most of my guitars, Maple at around.080-.090" and it extends out about 1/8" both sides of the bridge. I am wondering if it may not have been stiff enough and am thinking of putting a brace in right behind the Bridge plate. I have heard some people do this to stiffen up the bridge area.
Author:  charliewood [ Tue Jan 30, 2007 5:31 am ]
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Its a shame when people let thier instruments dry out to emaciated conditions - Im paranoid about it with my newest guitar, but its something that most players are less than expert about, and resistant to try to add moisture for fear of worsening rhe condition.
It would be beneficial for Guitar World or player rags like that to do a useful article like that in one of thier issues instead of the usual bio articles and articles about how Blink 182 formed and what thier plans are for thier latest er uughhh..... musical "creation".
Cheers
Charliewood
Author:  Alan Carruth [ Tue Jan 30, 2007 6:51 am ]
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You say that the bracing 'imprints' through the top: this makes it sound as though, if anything is too light, it's the top. Wood varies so much in stiffnes that, without testing it some way, and varying the thickness of the top to suit, it's easy to get too thin once in a while, unless you over build most of the time.

David Hurd's book, 'Left Brain Lutherie', has a lot to say about deflection testing. You can actually tell, from the start, whether your guitar top is over- or under-built this way. Basically, you use a dial gauge to see how much the top moves at a spot between the bridge and soundhole when the strings are brought up to pitch. The long-term deflection is generally proportional to the short-term, so too much immediate deflection is a sign of trouble to come. The only real drawback to this is that there are no 'canonical' numbers available yet: you sort of have to keep track and figure out over time what works and what doesn't. Still, if you gan get hold of several guitars that have stood the test of time you can compare them with the one you've got, and see if it's much worse. If it's not, then it's likely that the low humidty is at least part of the problem. Without some sort of measurement, you're never going to be able to sort this out.

That said, I'd be inclined to replace the top anyway. Yeah, it's a lot of work and a big drag. Sure, a heavier top won't sound like the one it's got now, and you'd better be sure the customer understands that well. But I keep thinking of the old rule of thumb: "When somebody buys something they like, they tell their friends. When they buy something they don't like, they tell _everybdy_." Can you take that sort of 'advertisement'?   
Author:  arvey [ Sat Feb 03, 2007 8:43 am ]
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well the guitar top has almost returned to it's original shape. so now I have to decide what o do. I would not describe what has happened as the bracing Imprinting through the top. It was more that the drop happened most noticable where there was no bracing, The bracing seems to have held it's shape better than the top wood which as you say allen may suggest the top wood was too light. As I said it is returning nicely to it's shape although it still hasn't gained its dome infront of the Bridge. Short of replacing the top (which I really don't want to do) is there any way to stiffen the top better so it can take the humidity extreams better. I was thinking of adding a bracre in front and behind the bridge and try to support it better that way. any other suggestions would be appreciated. I am thinking it would be best to not tour with this guitar but I know she wants to (her Takimaine she toors with does sound like crap to her now that she used this guitar on her last few CD's,
Author:  j.Brown [ Sat Feb 03, 2007 9:20 am ]
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Does this build a case for baking your tops and trying to minimize some of its shrink/swell potential?
-j.
Author:  LarryH [ Sat Feb 03, 2007 1:55 pm ]
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[QUOTE=arvey] well the guitar top has almost returned to it's original shape. so now I have to decide what o do. I would not describe what has happened as the bracing Imprinting through the top. It was more that the drop happened most noticable where there was no bracing, The bracing seems to have held it's shape better than the top wood which as you say allen may suggest the top wood was too light. As I said it is returning nicely to it's shape although it still hasn't gained its dome infront of the Bridge. Short of replacing the top (which I really don't want to do) is there any way to stiffen the top better so it can take the humidity extreams better. I was thinking of adding a bracre in front and behind the bridge and try to support it better that way. any other suggestions would be appreciated. I am thinking it would be best to not tour with this guitar but I know she wants to (her Takimaine she toors with does sound like crap to her now that she used this guitar on her last few CD's, [/QUOTE]

Arvey I didn't read where you say what caused or is causing the top to return to its shape? Can you give a few details?

Thanks

Larry
Author:  arvey [ Sun Feb 04, 2007 8:43 am ]
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Yes, I took nthe strings off and have had it in the shop where the humidity is controlled at 42-48% and it has had a planet waves humidifier in it and inside a case. At the same time there is a litle more than the orriginal dome behind the bridge and in front it is still flat. After started writing this the phone rang and it was Rita Chirellii, the artist who ownes this guitar. She gave me the name of the guy at the 12th fret who looked at it so I'll call him this week. any sugestions short of rplacing the top are appreciated otherwise I'll be replacing the top
Author:  AStass [ Sun Feb 04, 2007 3:35 pm ]
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I'd give the bridge Dr. a try, first, then, if that don't work, do something more drastic. I'm not a "real" luthier though. Alan.
Author:  arvey [ Mon Feb 05, 2007 2:26 am ]
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I really have no knowledge of the Bridge Dr. but will look into it.
Author:  arvey [ Sun Feb 11, 2007 4:34 am ]
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OK, this looks interesting, I notice that Breedlove guitars put them in all their new guitars, How does this effect sound? I see it uses Brass bridge pins when installed. I haven't been active here for the last bit as our town has been in a declared state of emegency this week and as Mayor that has taken a lot of time, But I still need to be working on this.
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