I once built a top in the house at 42% then took it out to the shop to carve braces on a low humidity day 20% or less. Pop went the wessel
center seam and x brace poped right off
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| Humidity Question (Part 2?) http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=5960 |
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| Author: | j.Brown [ Tue Apr 04, 2006 6:16 am ] |
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Hopefully some of you wood gurus can answer this. I live in a condo, but without the facilities that the Hesh-meister has. I don't have a "shop" per-se, but I do take Robbie O'Briens class at a school with a very well endowed woodworking lab, although one of the driest places one could wish to work. 20% Humidity typically. Up to 23-24% when the portable humidifier is running (it runs out of water fast). I tend to cart my guitar around a lot as I can work on small portions at home. My question is: Since I do have some humidity control at home (I can keep it around 40% in our small place), but not at the shop, is it good to keep moving it from dry to normal humidity a lot, or would it be better to leave it dry at home, too in order to prevent so much variation? Sorry for the long winded question and thanks in advance. -j. |
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| Author: | Joe Beaver [ Tue Apr 04, 2006 8:43 am ] |
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Sounds to me like both places you frequent are pretty dry. I'd say use a humidifer in your case and live the guitar in the case as much as possible. I'm guessing it will be ok... |
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| Author: | Michael Dale Payne [ Tue Apr 04, 2006 8:47 am ] |
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If you glue up in 50% then move it to 20% expect seams and joints to pop loose due to contraction from loss of moisture. On the other hand if you build in 20% and move to 50% expect swelling this in my opinion is the lesser of two evils, but if you do things like extend your braces through the rim, then as they expand they can push bindings away from the lining. In other words any drastic change has its own set of consequences it is best to build to completion in one environment. It is never a good idea to change environments during construction. I build in 35%-38%, but the complete the build in that enviroment. A completted guitar can adapt to an inviroment with in reason but like I said it is never good to change inviroments during the construction process |
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| Author: | Pwoolson [ Tue Apr 04, 2006 8:51 am ] |
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the good news in your situation is that it's better to build dry than to build wet. As Joe said, I would use a humidifier in a case and have it in the case as much as possible. You might want to find a way to do the major gluing operations at home where the humidity is closer to idea. Perhaps clear off the kitchen table for brace gluing, joining top and back. |
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| Author: | Michael Dale Payne [ Tue Apr 04, 2006 8:55 am ] |
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I once built a top in the house at 42% then took it out to the shop to carve braces on a low humidity day 20% or less. Pop went the wessel center seam and x brace poped right off
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| Author: | Grant Goltz [ Tue Apr 04, 2006 8:56 am ] |
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Excuse me, but wood does not expand longitudinally, so how can braces expand and push bindings away from the linings? As I said in another thread, If you are going to be a competant luthier, you need to learn the basics of how wood behaves. Then the myths and disinformation will cease and folks can get meaningful answers. Sorry for the rant, but I have read too much of this kind of thing on too many forums for a long time and it does nothing to help anybody 
Grant |
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| Author: | Grant Goltz [ Tue Apr 04, 2006 8:59 am ] |
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[QUOTE=MichaelP] I once built a top in the house at 42% then took it out to the shop to carve braces on a low humidity day 20% or less. Pop went the wessel center seam and x brace poped right off[/QUOTE]
I would suggest you change to a different glue. If this is actually happening there is more wrong than a simple change in humidity. Grant |
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| Author: | Mattia Valente [ Tue Apr 04, 2006 9:11 am ] |
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Well, no, the top shrinks, ergo the brace ends stick out too far, and pop off the binding. There used to be a photo and explanation of this on Larrivee's website, as a graphic warning about keeping your isntrument humidified. |
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| Author: | Grant Goltz [ Tue Apr 04, 2006 9:24 am ] |
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[QUOTE=Mattia Valente] Well, no, the top shrinks, ergo the brace ends stick out too far, and pop off the binding. There used to be a photo and explanation of this on Larrivee's website, as a graphic warning about keeping your isntrument humidified.[/QUOTE] Exactly, but saying that the braces swell is very misleading and confusing, especially to new builders. Grant |
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| Author: | Joe Beaver [ Tue Apr 04, 2006 10:22 am ] |
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[QUOTE=Grant Goltz] Excuse me, but wood does not expand longitudinally Grant[/QUOTE] But it does, just to a lesser degree than laterally. 
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| Author: | Pwoolson [ Tue Apr 04, 2006 10:32 am ] |
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[QUOTE=Grant Goltz] Excuse me, but wood does not expand longitudinally, Grant[/QUOTE] Grant, though wood expands 5x more laterally, it does indeed expand longitudinally. And if a brace were tucked into the linings and butted against the binding, expansion in this directon could definately pop the binding. Combine that with the top moving all over the place due to humidity, and you have serious problems. |
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| Author: | Joe Beaver [ Tue Apr 04, 2006 10:37 am ] |
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Shrinkage of red spruce: Tangential: 7.8% Radial: 3.8% That is from green to 8% MC Just so you know. |
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| Author: | Grant Goltz [ Tue Apr 04, 2006 3:02 pm ] |
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[QUOTE=Pwoolson] [QUOTE=Grant Goltz] Excuse me, but wood does not expand longitudinally, Grant[/QUOTE] Grant, though wood expands 5x more laterally, it does indeed expand longitudinally. And if a brace were tucked into the linings and butted against the binding, expansion in this directon could definately pop the binding. Combine that with the top moving all over the place due to humidity, and you have serious problems. [/QUOTE] Sorry, but on the length of a brace you would be hard pressed to measure any change. It is the other things, top and back, shrinking and swelling across the width that is what matters. Grant Grant |
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| Author: | Pwoolson [ Tue Apr 04, 2006 3:17 pm ] |
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[QUOTE=Grant Goltz] [QUOTE=Pwoolson] [QUOTE=Grant Goltz] Excuse me, but wood does not expand longitudinally, Grant[/QUOTE] Grant, though wood expands 5x more laterally, it does indeed expand longitudinally. And if a brace were tucked into the linings and butted against the binding, expansion in this directon could definately pop the binding. Combine that with the top moving all over the place due to humidity, and you have serious problems. [/QUOTE] Sorry, but on the length of a brace you would be hard pressed to measure any change. It is the other things, top and back, shrinking and swelling across the width that is what matters. Grant Grant [/QUOTE] Ok, you must be more of an expert than I so I'll let it go here. |
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| Author: | Robbie O'Brien [ Tue Apr 04, 2006 3:37 pm ] |
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The braces don't actually expand. The back contracts and the braces don't. The bindings are therefore pushed away from the sides. sorry, should have read the other posts before adding my comments. It seems that others have already said this. |
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| Author: | Grant Goltz [ Tue Apr 04, 2006 11:54 pm ] |
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[QUOTE=Joe Beaver] Shrinkage of red spruce: Tangential: 7.8% Radial: 3.8% That is from green to 8% MC Just so you know.[/QUOTE] Actually, shrinkage values normally given for wood are from fiber saturation point moisture (roughly around 30% for most species) to 0% moisture. From green (which can be over 100% moisture) to fiber saturation point moisture, there is no shrinkage. Grant |
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