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| Upper transverse question http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26367 |
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| Author: | James A. [ Thu Mar 04, 2010 11:37 pm ] |
| Post subject: | Upper transverse question |
I am currently on my first build and loving it. I am having fun, but who knows how this guitwang is going to sound. Right now I have the top and back finished and braced, and the sides are bent. When I glued the braces on, I radiused the upper transverse. Now I am learning that I probably should not have done that so that the upper bout area would be flat to better accommodate the fret board extending onto the guitar. My question is this, how many do this, and how big of a deal is it? Should I take the upper brace off and make a new one, or should I just chalk this one up as a learning experience? Any help is appreciated. |
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| Author: | Colin North [ Fri Mar 05, 2010 3:33 am ] |
| Post subject: | Re: Upper transverse question |
There have been other discussions about this in recent weeks. My OM, Kinkead, 25' radius top, 25' radiused sides before gluing top - I radiused the UTB to 25' like yours and as per plan, and sanded the upper bout flat (120 and 180 grits either side of a board supported on a 3mm piece of cork at the bridge centre, (located with a 3mm bamboo skewer through hole drilled in top/bridgeplate, avoiding bridgepin hole area ) This removes approximately 0.5mm (0.0125") of wood. If your top is 3mm as plan, this leaves 2.5 mm thickness, with neck block and top braceplate above UTB (2.5mm thick) as aditional support for the top. Some do this, some do it other ways - see Hesh's tutorial for example. http://luthiersforum.com/forum/viewtopic.php?f=10117&t=25931 Mine has been played for 14 months now, no sign of any problem, but you will have feedback from others I am sure. |
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| Author: | Hesh [ Fri Mar 05, 2010 6:29 am ] |
| Post subject: | Re: Upper transverse question |
James lots of guitars have been successfully built with radiused UTB's. I flatten the upper bout both at the rim flat sanding the rim face down from the waist up and with no radi imparted to the UTB. Just another method of prepping the box for fitting the fretboard extension. I do find it easier to fit the fretboard extension once I flatten the upper bout but again it's not the only way to accomplish this. With an upper transverse brace with a radi in it you can flatten the upper bout after the box is closed as I think that Colin is describing. There are jigs that register off the neck and then swing back and forth not unlike the thing that swings back and forth on a grandfather clock sanding the upper bout of the top where the fret board extension will be flat. Colin's done the math too estimating how much top will be left. Not sure if you will get much fall-away this way and of course what you want to avoid at any cost is having the fret board extension ramp upward before it terminates. No worries I can see that you can make this work without removing the UTB if you sand the upper bout flat. If you look at the toot that I did you will see some of the objections that others have to the method that I describe (also could be called the Martin method since they flatten the upper bout too) and some objections to sanding the upper bout and radiusing the UTB but either approach can work fine IMHO. Hey you are making good progress - congrats! |
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| Author: | meddlingfool [ Fri Mar 05, 2010 1:29 pm ] |
| Post subject: | Re: Upper transverse question |
I radius all of mine. Then when I rough fit the neck, I leave the fretboard sitting proud about the thickness of a sheet of notebook paper. I then draw witness lines with pencil between the dovetail and the soundhole extending past where the edge of the fretboard will be. Then I take a flat block around 8"x4" with 100 grit and sand lightly from the dovetail to the soundhole until the lines are gone and the dovetail is flush with the top. I say sand lightly because you can compress the UTB by pushing on it too hard, causing it to "spring" back up when younthink you're done. Therefore of course, check your efforts with a straightedge before gluing the FB. This has worked very all for me on 45 guitars, 0 humps. Mind you, I radius my FB's after the neck is glued on. Cheers |
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| Author: | Darryl Young [ Fri Mar 05, 2010 2:00 pm ] |
| Post subject: | Re: Upper transverse question |
Todd Stock wrote: The advantage to a radius on the UTB is that the upper bout will likely not end up going concave after a few years, which is pretty common. Excellent point Todd.....thanks for pointing that out. A little arch is probably a good thing. |
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