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| Braces telegraphing through the Top? http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=11360 |
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| Author: | j.Brown [ Fri Mar 23, 2007 4:35 am ] |
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My top appears to be very clean, very level, and I’ve sanded to around 150 grit. Now I’m sanding my FB down and the ebony dust that gets everywhere is collecting rather conspicuously and is telegraphing my X-brace through the top. The braces don’t appear when its just sanded and its only the X braces, not any of the others. It brushes off easily and is not a problem right now, its just strange. Any idea why that is happening? Is it common? If its happening with ebony dust, does that signal a problem with finishing later? Sorry I don’t have any photos. Thanks -j. |
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| Author: | crazymanmichael [ Fri Mar 23, 2007 5:24 am ] |
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why is the ebony dust getting on the top? it is more common to finish steel strings as two pieces, the neck separate from the body. how thick is the top? has the top gone through any significant rh changes since it was braced and or glued to the rim? |
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| Author: | j.Brown [ Fri Mar 23, 2007 5:40 am ] |
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I need another mm lower at the saddle, so I'm sanding it that way. The top is 2.3 - 2.5mm thick. 30' radius. No major changes. Not really any minor changes, either. Its been kept in a 35% humidified room since it was closed. We're at about 20-25% ambient humidity on a daily basis here in colorado. |
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| Author: | Robbie O'Brien [ Fri Mar 23, 2007 6:01 am ] |
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J, My guess is that it is static electricity that is causing the dust to collect on the top outlining the X-brace. |
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| Author: | crazymanmichael [ Fri Mar 23, 2007 6:10 am ] |
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i am puzzled by your reference to lowering the saddle being the cause for sanding the fb? |
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| Author: | Kirt Myers [ Fri Mar 23, 2007 6:11 am ] |
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Maybe you can hold it up at a long angle to a single light source and see if you see any shadows. Kirt |
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| Author: | SteveCourtright [ Fri Mar 23, 2007 6:19 am ] |
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J. The top is not moving over the braces as much so the ebony dust tends to stay put there. Where the top is moving, (from the vibrations to the top from sanding) the dust tends not to collect because it is either being vibrated off or air moving from the top vibrating tends to discourage the very fine dust from settling on the moving parts of the top. Just my theory. In other words, the braced part of the top is like a node, which vibrates less than other parts of the top and the dust settles on the nodes more easily than other parts of the top. |
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| Author: | npalen [ Fri Mar 23, 2007 7:32 am ] |
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Steve--You may be on to something here, another variation of the glitter test? |
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| Author: | Kevin Gallagher [ Fri Mar 23, 2007 7:49 am ] |
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j.brown, It's just a matter of the higher vibration of the areas between the braces causing the dust to dance on the top until they reach the braced areas where it isn't able to vibrate as freely and the dust settles there. It's the same concept as the powder readings arrived at through Chladnii technology. The top is charged with a tone and caused to vibrate and the powder dances around and settles into the non vibrational or less vibrational areas. It's typical and is certainly nothing to worry about. Your top thickness is fine and the indication that simple and subtle vibrations caused by ambient sound are activating it to the point where it causes the powder to find a resting spot. Regards, Kevin Gallagher/Omega Guitars |
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| Author: | j.Brown [ Fri Mar 23, 2007 9:40 am ] |
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Thats pretty interesting. So not so much a matter of the x braces attracting the dust as it is that the rest of the top is repelling it or moving it away. I hope that holds true, cuz thats an excellent thing to be happening. 
Thanks for the info. -j. |
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