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Cablepuller
PostPosted: Tue Jun 09, 2015 7:35 am 
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Hi

Have routed a oversize binding channel ok and thinned the back down as it was to thick. .but

The back somehow went concave on me today..
Had a definite dome yesterday..worked on the guitar outside so maybe the heat/humidity did it

Any ideas..not keen on cutting it off

Can i steam it ?

Heres some pics
ImageImageImage
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meddlingfool
PostPosted: Tue Jun 09, 2015 7:46 am 
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Brazilian Rosewood
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First name: Ed
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City: Nanaimo
Country: Canada
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Get it into a known and monitored RH controlled environment at around 40-45% RH for a few days and see what happens.


These users thanked the author meddlingfool for the post: Cablepuller (Tue Jun 09, 2015 8:35 am)
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Michael.N.
PostPosted: Tue Jun 09, 2015 7:51 am 
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Not to worry. These problems keep on coming. I've been at this stuff for decades and I still keep hitting problems!
That's a severe turn around, especially if it's gone from convex to concave. I've had that happen only once and that was because I wasn't monitoring humidity levels in my UV cabinet.
You can try to rehumidify. I suspect it won't get back to normal though. I also build flat backed instruments and they go concave readily. They never get back to normal. That's part of the instrument type and is acceptable. Doesn't seem to do much harm to them.
What glue did you use?


These users thanked the author Michael.N. for the post: Cablepuller (Tue Jun 09, 2015 8:36 am)
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Tom West
PostPosted: Tue Jun 09, 2015 8:30 am 
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Cable: Not sure of your normal RH for this time of year but here in N.S. if that happen in the spring or summer I would be in serious trouble in the winter. I suspect you braced in too high a RH level. I know you are not going to like what I say but suggest you take your back off, take off the braces, thin the back, get a handle on RH, then rebrace and reglue your back on the sides.
Tom

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These users thanked the author Tom West for the post: Cablepuller (Tue Jun 09, 2015 8:36 am)
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Cablepuller
PostPosted: Tue Jun 09, 2015 8:40 am 
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Michael.N. wrote:
Not to worry. These problems keep on coming. I've been at this stuff for decades and I still keep hitting problems!
That's a severe turn around, especially if it's gone from convex to concave. I've had that happen only once and that was because I wasn't monitoring humidity levels in my UV cabinet.
You can try to rehumidify. I suspect it won't get back to normal though. I also build flat backed instruments and they go concave readily. They never get back to normal. That's part of the instrument type and is acceptable. Doesn't seem to do much harm to them.
What glue did you use?

Haha these problems certainly do.. im a bit calmer about it all now as realised my first scratch build is more about learning than anything else

Used titebond.. think the sun hitting the back at one stage did it.. doh

What do the flat backs sound like and are they ok when they go a bit concave

Cheers
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Haans
PostPosted: Tue Jun 09, 2015 8:56 am 
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Suggest you listen to what Tom West said. If you do not get your RH under control, you will continue to have problems.


These users thanked the author Haans for the post: Cablepuller (Tue Jun 09, 2015 9:23 am)
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Michael.N.
PostPosted: Tue Jun 09, 2015 9:36 am 
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Cablepuller wrote:
Michael.N. wrote:
Not to worry. These problems keep on coming. I've been at this stuff for decades and I still keep hitting problems!
That's a severe turn around, especially if it's gone from convex to concave. I've had that happen only once and that was because I wasn't monitoring humidity levels in my UV cabinet.
You can try to rehumidify. I suspect it won't get back to normal though. I also build flat backed instruments and they go concave readily. They never get back to normal. That's part of the instrument type and is acceptable. Doesn't seem to do much harm to them.
What glue did you use?

Haha these problems certainly do.. im a bit calmer about it all now as realised my first scratch build is more about learning than anything else

Used titebond.. think the sun hitting the back at one stage did it.. doh

What do the flat backs sound like and are they ok when they go a bit concave

Cheers


Titebond should release with careful heat. Obviously not too hot because you don't want to scorch anything.
A strong alcohol also turns it into gel but that's probably a longer method.
I have a parting knife that I put into near boiling water, then zip along the seam. There are a few ways to do it but because you haven't a finish on the instrument apply heat from the outside of the Back. Just take it easy and don't feel rushed. Patience is more than a virtue when it comes to repair techniques.


These users thanked the author Michael.N. for the post: Cablepuller (Tue Jun 09, 2015 9:44 am)
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Cablepuller
PostPosted: Tue Jun 09, 2015 9:45 am 
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Ok hopefully sorted ..steamed the back with a bit of weight inside and seems back to normal..fingers crossed
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DennisK
PostPosted: Tue Jun 09, 2015 10:31 am 
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Tom West wrote:
Cable: Not sure of your normal RH for this time of year but here in N.S. if that happen in the spring or summer I would be in serious trouble in the winter. I suspect you braced in too high a RH level. I know you are not going to like what I say but suggest you take your back off, take off the braces, thin the back, get a handle on RH, then rebrace and reglue your back on the sides.
Tom

+1 to that. My humidity has been way high for the past month or so, and just dropped to medium yesterday, so if you live somewhere in the same climate zone, that's probably what happened. Back up some today so it may poof back up for the moment, but if it's going concave from medium humidity, it will be toast in the winter.

Cablepuller wrote:
Used titebond.. think the sun hitting the back at one stage did it.. doh

I actually use sunlight to dry things before bracing sometimes :) If the humidity isn't too terribly high, leave it in a sunny window for a few hours and it should get nice and dry. Maybe 10-15% drop from the room humidity.

Quote:
What do the flat backs sound like and are they ok when they go a bit concave

Most of my guitar backs alternate between convex and concave throughout the year. Doesn't seem to affect the sound too much.


Last edited by DennisK on Tue Jun 09, 2015 10:34 am, edited 1 time in total.

These users thanked the author DennisK for the post: Cablepuller (Tue Jun 09, 2015 10:32 am)
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Cablepuller
PostPosted: Tue Jun 09, 2015 10:33 am 
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DennisK wrote:
Tom West wrote:
Cable: Not sure of your normal RH for this time of year but here in N.S. if that happen in the spring or summer I would be in serious trouble in the winter. I suspect you braced in too high a RH level. I know you are not going to like what I say but suggest you take your back off, take off the braces, thin the back, get a handle on RH, then rebrace and reglue your back on the sides.
Tom

+1 to that. My humidity has been way high for the past month or so, and just dropped to medium yesterday, so if you live somewhere in the same climate zone, that's probably what happened. Back up some today so it may poof back up for the moment, but if it's going concave from medium humidity, it will be toast in the winter.

Cablepuller wrote:
Used titebond.. think the sun hitting the back at one stage did it.. doh

I actually use sunlight to dry things before bracing sometimes :) If the humidity isn't too terribly high, leave it in a sunny window for a few hours and it should get nice and dry. Maybe 10-15% drop from to the room humidity.

Quote:
What do the flat backs sound like and are they ok when they go a bit concave

Most of my guitar backs alternate between convex and concave throughout the year. Doesn't seem to affect the sound too much.

Thanks dennis
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Haans
PostPosted: Fri Jun 12, 2015 6:23 am 
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You need a humidifier and dehumidifier and need to use them religiously. Humidity needs to be a constant 45%.


These users thanked the author Haans for the post: Cablepuller (Fri Jun 12, 2015 12:17 pm)
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kencierp
PostPosted: Fri Jun 12, 2015 8:55 am 
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First part of the video = guidelines regarding humidity controls and why its so important.
https://www.youtube.com/watch?v=vd5mGrV6Lck

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These users thanked the author kencierp for the post: Cablepuller (Fri Jun 12, 2015 12:17 pm)
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Cablepuller
PostPosted: Fri Jun 12, 2015 12:23 pm 
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kencierp wrote:
First part of the video = guidelines regarding humidity controls and why its so important.
https://www.youtube.com/watch?v=vd5mGrV6Lck

Intresting video thanks ken..
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Clay S.
PostPosted: Sat Jun 13, 2015 9:29 am 
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Brazilian Rosewood
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If you carefully saw the back off you can solve both of your problems - eliminate the oversize binding ledge and rebrace the back at the proper humidity level and arching so (although it will "flatten"some) it will not go concave. Concave backs and overly large bindings are mostly a "looks" thing, which would bug me, but if you don't mind, the guitar should still work.


These users thanked the author Clay S. for the post: Cablepuller (Sat Jun 13, 2015 10:37 am)
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