#76
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Rodger Knox, PE 1917 Martin 0-28 1956 Gibson J-50 et al |
#77
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I would wager that if you affixed a hardwood board to your wall, and glued a bridge to it, whether with TiteBond or hide glue, you (and possibly I) could hang off that bridge without incident. I would contend if you affixed that same board to the ceiling, you could hang off the bridge. If stress concentrations were of such concern in bridge design that the wings were tapered, then how come not the back of the bridge? Is it because the bridge plate extends past the bridge back, moving the localized bend point away from the back of the bridge? I'm pretty sure bridge "tipping" has been known ever since the advent of the fixed bridge. For an extreme example, take two 1/2" plates of Lexan. Fix one on a table, spritz some water on the surface, then press the second sheet down. It would be all but impossible to lift off. You may be able to push or pull it front to back or side to side. Now, do the same experiment, but replace the top sheet with 1/16" Lexan. You still couldn't lift that sheet straight up, but if you got a hold of a corner and bend it up, it would then take little effort to "peel" that thin sheet away. Now take that same 1/16" sheet, and glue bracing over the sheet resembling a box frame and joists as on a ceiling. It would likely behave closer to the 1/2" sheet as far as trying to pull it off the bottom sheet, but it would be slightly more flexible, that if you pushed it far enough over the edge, you could bend the sheet enough that it starts to "peel away" from the bottom sheet. This "top sheet" represents the top of the guitar, and the bottom sheet represents the bridge. Since the bridge is thicker than the soundboard by a factor of about 3 or 4, and made of a denser material, it's unbendable in relation to the soundboard. My point is, if you mitigate flexing of the top at the point of the back of the bridge, then the bridge and soundboard will tip "together" as if it were on a hinge at that point Dave Malicky describes, leaving any failure in the joint as a result of either glue failure or wood fiber failure. From my ear with my limited experience, the difference would be that the guitar would sound less "vintage" and "dry" for lack of better word, but maybe tighter in the bass. I feel the strings feel a little more "stiff" as well, regardless of gauge. Quote:
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#78
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This thread was started as nothing more than an exercise, a discussion of what might be possible, and why or why not. And I feel it was a very good discussion, with a lot of very fine fellow's inputting their expertise and experience into it, including yourself. My 'Hat's ' off to all for a fine discourse!
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#79
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#80
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IMHO, guitars sound better when the bridgeplate does not extend past the bottom edge of the bridge, so that is the way I build them. in any case, a conventional bridgeplate with the grain perpendicular to the grain in the top is not the best for reinforcing the top against peeling. That is because most woods are more flexible across the grain than with the grain. Spruce is much stiffer along the grain than across, making it very suitable for resisting the peeling in the direction of string pull. The key is to choose wisely....both the stiffness of that particular piece of spruce, and the final thickness. Couple that with string gauge, bridge width (1" wide rectangular or a wider belly) and string height above the top to arrive at the ultimate design. With the right choices, the guitar can sound great AND last more than a lifetime. The best prewar examples prove that. |
#81
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#82
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__________________
Rodger Knox, PE 1917 Martin 0-28 1956 Gibson J-50 et al |