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Fasterthanlight
 Post subject: Humidity and Back Braces
PostPosted: Thu Apr 16, 2020 11:12 am 
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First name: Gary
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So i was in my own world today gluing back braces on and when i realised i hadnt checked the humidity... it turned out to be 35% and i had already finished gluing.

How much of a problem is this? Should i be stripping of the braces and starting again when at 45%??

Thanks.

G.
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rbuddy
PostPosted: Thu Apr 16, 2020 11:24 am 
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I build the box in ~35% RH on purpose. I believe greater risk is in higher RH conditions as that would put the plates in shrink mode more often than compression on average. The shrinking causes cracks.

Brian R

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Clay S.
PostPosted: Thu Apr 16, 2020 11:51 am 
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For back braces it shouldn't be too much of a problem (it's only 10 points off what many people suggest bracing at). For soundboards it might be good to brace closer to 45 -50% R.H. as the swelling and shrinking affects the action on a lightly built "responsive" guitar.


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doncaparker
PostPosted: Thu Apr 16, 2020 12:00 pm 
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rbuddy wrote:
I believe greater risk is in higher RH conditions as that would put the plates in shrink mode more often than compression on average. The shrinking causes cracks.


Agreed. If you are going to vary from the 40-45% range while doing a glue-up of guitar parts, it is better to build too dry than too wet. Swelling tends to cause fewer serious problems than shrinking.


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Colin North
PostPosted: Thu Apr 16, 2020 12:09 pm 
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Fasterthanlight wrote:
So i was in my own world today gluing back braces on and when i realised i hadnt checked the humidity... it turned out to be 35% and i had already finished gluing.

How much of a problem is this? Should i be stripping of the braces and starting again when at 45%??

Thanks.

G.

No worries at, you're only 8 deg. low in my book - high/normal RH and then drying out, now that can be potato chip time....

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TerrenceMitchell
PostPosted: Thu Apr 16, 2020 12:43 pm 
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Clay S. wrote:
For back braces it shouldn't be too much of a problem (it's only 10 points off what many people suggest bracing at). For soundboards it might be good to brace closer to 45 -50% R.H. as the swelling and shrinking affects the action on a lightly built "responsive" guitar.



Agreed. I live in Florida, and it's "never" dry... but I had a top that got braced on a day when the weather was unusually nice and I didn't realize the humidity was around 27%. Couple days later the thing wouldn't lay flat in the solera for nothing. Had to put it back in the go deck and heat up the braces until they "slid" a little. But, this is why we use hide glue! Guitar ended up sounding great with no problems.
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Fasterthanlight
PostPosted: Fri Apr 17, 2020 2:03 am 
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Thanks guys... so what i'm hearing is, it shouldnt be a problem.. go ahead. Better a bit too dry that too wet?

G.

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SteveSmith
PostPosted: Fri Apr 17, 2020 6:35 am 
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Yep

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Joe Beaver
PostPosted: Sat Apr 18, 2020 12:44 pm 
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I prefer to make and install my braces during low RH times. 30-35 percent sounds like a good time to me.

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