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| string tensions and bracing http://luthiersforum.com/forum/viewtopic.php?f=10101&t=46005 |
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| Author: | mike-p [ Sat Jul 11, 2015 5:39 am ] |
| Post subject: | string tensions and bracing |
Hi all, I've built a 13 fret l00 / nick lucas in cuban hog/ euro spruce and brw. I braced it from John Arnold s plan which he very kindly gave me a copy of. I shifted the bracing to where it would be for a twelfth fret model but then used a 25.5" scale. Plan was to try different guages and tunings. Not altered tunines, just a semi tone or tone lower. I messed about with the string tension calculator ams found that, roughly speaking going up or down from 24.75 scale to 25.5 changes the tension in a similar way to tuning up or down a semitone OR going up or down in string guages. In other words 24.75 scale, 12 guage, standard tuning Equals 25.5 scale, 12 guage, semitone low Equals 25.5 guage 13 guage, whole tone lower. I've got the third option on at the moment but would like to try tuning up a semitone or even a tone. Question is. How do you decide the maximum string tension for a particular guitar? I've tried 13s on forties Gibson jumbos ams they didn't like it. Thanks for the advice. I will post pics and hopefully a video when I have time/feel brave enough. The sound is very rich and very loud! |
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| Author: | Clinchriver [ Sat Jul 11, 2015 7:20 am ] |
| Post subject: | Re: string tensions and bracing |
My #2 is a 13 fret 24.750 scale, built from John Arnold's tracing of his 1937 14 fret Nick Lucas. With 12's it has a hint of "belly" on the top and has plenty of snap and volume. I would keep a close eye on the top behind the bridge. I like the lower tension of a 24.750 scale. We have a couple of tunes we play in dropped D and it sounds fine. I believe Santa Cruz makes a 25.5, 13 fret Nick Lucas style. Should be fun finding out. |
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| Author: | mike-p [ Sat Jul 11, 2015 7:27 am ] |
| Post subject: | Re: string tensions and bracing |
I was aware of the Santander cruz and basically pinched the idea but I suspect the bracing is different / heavier. |
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| Author: | mike-p [ Sat Jul 11, 2015 7:38 am ] |
| Post subject: | Re: string tensions and bracing |
I got to stop using the predictive text on my phoney. |
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| Author: | Alan Carruth [ Sun Jul 12, 2015 2:55 pm ] |
| Post subject: | Re: string tensions and bracing |
Trevor Gore suggests that the amount the bridge rotates forward is a good way to tell. He says that, in his opinion, a 'good' guitar should allow the bridge to rotate 2 degrees when the strings are tightened up. If it's more than that you risk trouble down the road, and less is probably making less sound than it could because it's over braced. I have to wonder if that specific number is 'holy', or whether different makers might find other numbers that work better for them. However, the general reasoning seems sound. |
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| Author: | kencierp [ Sun Jul 12, 2015 5:01 pm ] |
| Post subject: | Re: string tensions and bracing |
I really like Roger Siminoff's approach -- you'd need to make a fixture like in the link or get Roger's luthier's Handbook and make one like his. General idea is to calculate the total tension of the string set at pitch, judiciously shave the bracing until the sound board starts to defect -- that way you know the top will respond to energy from the tiniest string pluck/motion. http://community.berea.edu/guitarresear ... Tests.html |
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| Author: | mike-p [ Mon Jul 13, 2015 5:09 am ] |
| Post subject: | Re: string tensions and bracing |
Well with 13 guage tuned down a semitone I can see some belly but only got one degree of rotation with the app on my phone. A whole tone down is too deep and rich and you have to play everything really slowly. |
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| Author: | mike-p [ Mon Jul 13, 2015 5:15 am ] |
| Post subject: | Re: string tensions and bracing |
Think I've managed to add a picture. It's my third scratch build and the one I had difficulty sanding the upper bout angle. All sorted now, action at 2.5 - 2 mm very playable too. Finish is sprayed shellac and tru oil over the top, very pleased with it. Thanks for the help on this ams many other threads. More pictures and hopefully a video soon. |
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