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How long to leave top and back braced ?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=11007		 Page 1 of 1
Author:  Irwin R [ Mon Feb 19, 2007 4:17 am ]
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Well, trying to rebend by second side.. didn't work so I had to reorder a couple more sides


I have my braces all cut for my top and back and would like to get them glued and carved..I was waiting to get my sides bent so I could close up the box shortly after I bent them...Well now that may be a while ( couple of weeks)....Am I ok th brace the top and back and leave them for that long...I am manging to keep the humidity in the shop fairly constant at 45%..I have heard horror stories of them ( top  esp.) going out of shape if you don't get them closed up right away..


 


Any input greatly appreciated..Thanks
Author:  peterm [ Mon Feb 19, 2007 4:24 am ]
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if the humidity is not going to be a problem you can keep it braced for as long as you need...

The most important thing is to glue the braces at the proper humidity, if you glue them on at extremely low or high RH when it returns to normal you may have a "little" problem.
Author:  peterm [ Mon Feb 19, 2007 4:52 am ]
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Hesh you are right.

The important thing to also take into consideration is to mind the RH WHEN you do glue the top to the rim.... Equally as important as glueing the braces to the top.
Author:  JohnAbercrombie [ Mon Feb 19, 2007 5:17 am ]
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If you glue your braces while still 'in the square' - ie mostly unshaped, no scalloping or whatever- there is the possibility of leaving the shaping until the last minute. The (very) oversized rectangular braces should keep the top fairly stable if your humidity doesn't vary too much.

That's what I've done over the past few weeks and it did seem to work OK.

Cheers
John
Author:  LanceK [ Mon Feb 19, 2007 5:31 am ]
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In my very unorthodox building habits, I have had braced and scalloped tops as well as a stack of braced backs resting for well over a year with no detectable movement.
I make a habit of joining my the very moment that I know for sure what I will be using for a given guitar. This has significantly helped in the glue line sinking department.
Author:  Irwin R [ Mon Feb 19, 2007 5:47 am ]
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Wooo  Hooo!! Thanks guys..I think I'm good to go!!..I may take John's advice and leave them "in the square"


 


Thanks again!


 
Author:  JohnAbercrombie [ Mon Feb 19, 2007 6:18 am ]
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[QUOTE=LanceK]
I make a habit of joining my the very moment that I know for sure what I will be using for a given guitar. This has significantly helped in the glue line sinking department. [/QUOTE]
Lance-
You mean that the final sanding on the top flattens, with most of the glue shrinkage along the center join already having had its effect?
I hadn't thought of that issue at all- thanks. If I ever get working faster I'll have to pay attention to this!

Cheers

John
Author:  LanceK [ Mon Feb 19, 2007 6:46 am ]
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Hi John, yes
I have had glue shrink into the seam after the guitar was finish leaving a line. So to try to prevent this, I glue up the plates just as soon as I know what Ill be using.
Author:  Dave Rector [ Mon Feb 19, 2007 8:29 am ]
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[QUOTE=LanceK]I have had glue shrink into the seam after the guitar was finish leaving a line. [/QUOTE]

I have had the same thing happen. I have a coco/sitka dred hanging in the shop that has been there for over a year. I just haven't gotten around to fixing that sunken line.

I now do it like Lance does. As a matter of fact I think Lance was the one who told me about it. Thanks Lance!
Author:  JJ Donohue [ Mon Feb 19, 2007 12:39 pm ]
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It wouldn't hurt if you could leave the braced top in it's corresponding radiused dish with gobars to maintain the dome until you get around to gluing it to the sides.

One of my highly respected mentors once "strongly encouraged" me to get the plates glued to the sides immediately after voicing. I have since followed his advice.
Author:  nathan c [ Mon Feb 19, 2007 12:51 pm ]
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Ok, Lance, Dave, the noob doesn't understand. The glue line on the seam of the back will actually concave somewhat? Is that what you guys are saying?
Author:  Dave Rector [ Mon Feb 19, 2007 4:23 pm ]
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Nathan, I am saying that the glueline actually sunk, leaving a shallow line under the lacquer finish. I sanded things level and shot several more coats and it sunk again. I'm still not sure what it will take to fill it since I haven't gotten back to it yet.
Author:  Irwin R [ Mon Feb 19, 2007 10:27 pm ]
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Sorry , and what are you fellas saying may have caused this?
Author:  nathan c [ Tue Feb 20, 2007 12:24 am ]
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Irwin, you're not alone .

Dave, thanks I now understand what you guys meant by a sunken glue line.

[QUOTE=LanceK] In my very unorthodox building habits, I have had braced and scalloped tops as well as a stack of braced backs resting for well over a year with no detectable movement.
I make a habit of joining my the very moment that I know for sure what I will be using for a given guitar. This has significantly helped in the glue line sinking department. [/QUOTE]
Lance, sorry, but as someone else on the OLF has already said, "I am a product of the Alabama public school system." Are you saying that because you joined and braced the plates immediately and let them set that there has been less problems with the glueline sinking? Or was the second part just an aside. Since the joined plates set longer then there was less chance of glue shrinking after finishing. Whether braced or not.
Author:  JJ Donohue [ Tue Feb 20, 2007 1:59 am ]
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[QUOTE=LanceK] Hi John, yes
I have had glue shrink into the seam after the guitar was finish leaving a line. So to try to prevent this, I glue up the plates just as soon as I know what Ill be using. [/QUOTE]

Lance...I'm a bit confused on this as well. Whan you get a sunken seam, how long does it take to reveal the sink? Do you fill it in with additional glue before gluing the top or back to the sides? Could you also do the fill once it is glued to the sides just as effectively?

Please clarify...Thanks.
Author:  Dave Rector [ Tue Feb 20, 2007 4:33 am ]
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JJ, I'm not Lance but I can tell you what happened to me. I did not see the line where the glue sank before finishing the guitar. I didn't even see it after all the finish coats were on. After letting it hang for about a month I went back to do final sanding and buffing. There it was!

I sanded it back down and wiped it with naptha and nothing showed up so I sprayed some more finish on it and hung it back up to cure again. When I looked at it a couple of weeks later, there it was again. Not quite as bad this time, but it was there.

That's as far as I have gotten with it. I've been sidetracked by other projects and just never get around to it. I'll probably have to sand the back all the way back to wood and use some epoxy as a filler before I can try again.
Author:  Brock Poling [ Tue Feb 20, 2007 1:07 pm ]
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You could probably add more finish and level sand it and buff it.

But the glue continues to shrink for a while and if you build fast the glue isn't fully hardened by the time you get to finish and when it dries full and continues to shrink back you get a "ditch" on the center line.

There is a fix for this though... epoxy.   
Author:  nathan c [ Wed Feb 21, 2007 12:00 am ]
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Thanks Brock, I think I got it now. It sounds like I need to go ahead and join the plates for #2 while I'm working on #1.
Author:  Howard Klepper [ Wed Feb 21, 2007 5:21 am ]
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How thick a glue line are you guys getting? I've never had this problem.

But I do think that a finish check along the center line is common, because the wood on either side of the line is moving away from the line when humidity drops.
Author:  Brock Poling [ Wed Feb 21, 2007 6:16 am ]
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I notice though that I only see this line with titebond.

Author:  Dave Rector [ Wed Feb 21, 2007 7:30 am ]
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[QUOTE=Brock Poling]
I notice though that I only see this line with titebond.
[/QUOTE]

That's my experience as well Brock.

Also, I idd sand this all the way back to bare wood and rebuild the finish in the center. After it cured for a couple of weeks there was the line again.

One of these days I'll get around to fixing it....
Author:  Colin S [ Wed Feb 21, 2007 9:42 am ]
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Like Howard said. I always join my plates with HHG and can barely see where the line is, never mind if it's shrunk. What glue are you using Lance?
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