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| Top movement by adding string tension http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=53175 |
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| Author: | guitarjtb [ Wed Apr 29, 2020 7:54 pm ] |
| Post subject: | Top movement by adding string tension |
Approximately how much do your tops rise, when going from no string tension to full string tension? |
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| Author: | Colin North [ Thu Apr 30, 2020 3:17 am ] |
| Post subject: | Re: Top movement by adding string tension |
From WoodyG - We measure using the underside of the D string (usually the highest string), and always include body distortion as opposite sign of the other numbers. Dread, GA, SJ, and other larger guitars see 1/16"(1.5mm) of 'top rise' (really, body distortion) which serves to drop string height over the top once action is readjusted, while a 000 or OM may see 0.045"(1.14mm), and an O and smaller between 0.030"(0.76mm) (O) and 0.017" (Size 5). Obviously, these numbers are for planning - top thickness, bracing, and body construction will determine just how much the body changes shape (and how long that takes) under string tension. and other comments - http://luthiersforum.com/forum/viewtopic.php?f=10101&t=52369 |
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| Author: | guitarjtb [ Thu Apr 30, 2020 8:45 am ] |
| Post subject: | Re: Top movement by adding string tension |
Thanks, Colin. That thread gives me the information I was looking for. James |
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| Author: | J De Rocher [ Thu Apr 30, 2020 8:21 pm ] |
| Post subject: | Re: Top movement by adding string tension |
I've never looked at this on my guitars and I got to thinking and realized I have the numbers in my build notes to calculate how much the top rises. Before I make the bridge and saddle, I use a straight edge to project fret plane to the position of the saddle, measure the height above the top, and add 5/32 (corresponding to 5/64 action at the 12th fret) to that to decide how tall to make the bridge and the saddle blank as a starting point for fitting the bridge plus saddle to the top. After the guitar is strung up, I know what the combined height of the saddle plus bridge is after having set the final action. The difference is how much the top moved upward. I pulled numbers from my notes for two dreadnoughts, two of my middle-size guitars, and two parlor guitars. Top movement Dreadnoughts: 0.073" and 0.103" Mid-sized: 0.096" and 0.044" Parlor: 0.061" and 0.026" The octave mandotar I just finished: 0.077" It's interesting to me that, to my ears, the numbers don't really correspond to how loud, bright, or bassy they sound. The parlor guitar that had only 0.026" of movement is the only one of these guitars with tapered rather than scalloped x-braces. I don't know if that has anything to do with it. That guitar sounds killer when played with finger picks. |
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