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Type: Posts; User: Dave Cohen

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    Re: Bowl back science

    There are some things about their "first 12 eigenmodes" figure that seem squirelly to me. I'll have to read the pape carefullyr to be sure. Looks to me like modes 1 and 2 are probably the same...
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    Re: Bowl back science

    THe longitudinal (aka parallel) modulus does indeed follow density. However, the cross-grain (aka perpendicular) modulus can be all over the map, and for a variety of reasons. Per Graham...
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    Re: Bowl back science

    I just skimmed the article yesterday, but took away a few things that I already knew - sorta. At one point, I did interferometry and a few other things on a 1921 (?) Calace that Mike Schroeder had...
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    Re: Neck reinforcement vs a truss rod

    Just looked at StewMac's site again. The figures I saw for the masses of Waverly tuners varied between 170g and 290 g. Something haywire there. Also put off by their sloppiness with significant...
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    Re: Neck reinforcement vs a truss rod

    I weigh everything - all instrument parts, hardware, etc.,... - on my Mettler toploading balance. The more recent Golden Age tuners I have weighed did indeed weigh ~150 grams, +/- 1 gram. Haven't...
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    Re: Neck reinforcement vs a truss rod

    The balance point on most mandolins ranges from under the neck heel to just slightly toward the tailpiece from the neck heel. A greater concentration of mass toward the headstock affects the moment...
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    Re: Neck reinforcement vs a truss rod

    Titanium metal has a density of ~4.5 g/cm3; the density of iron is ~7.8. So that'll save about 43% compared to the mass of a steel truss rod. So a Ti rod would be in the neighborhood of 17 g. ...
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    Re: Neck reinforcement vs a truss rod

    John, as I remember it, you ground away part of the rod to reduce mass, Is that still the case?

    Re replacing the maple with spruce: I would emphasize the "...very slightly...." in your post. In...
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    Re: Neck reinforcement vs a truss rod

    Like James, I prefer the use of CF reinforcement rather than a truss rod. The metals from which truss rods are made have densities in the 7-8 g/cm3 range. They are replacing wood which has a...
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    Re: Lutherie as an art form

    I can't help myself form taking personally the reference to "......the pedantic chest beating of stuffy academics.....". Dunn0 what constitutes art vs artisanry vs craft vs ???. I have a cousin who...
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    Re: Effect of bridge breakover angle.

    I've imaged the mandolin body modes both with and without a bridge and strings in place. I found no difference in either mode shapes or modal. frequencies, with only one exception. One mandolin had...
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    Re: Effect of bridge breakover angle.

    Given that the soundpost in bowed string instruments is a literal connection between its location on the top plate and its location on the back plate, it would seem obvious that the soundpost also...
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    Re: Effect of bridge breakover angle.

    I need to be more careful about using science jargon. "Dynamical forces" just means forces that are changing continually with time, in this case, forces due to the MOTION of the strings. Strings...
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    Re: Truss rod and carbon fiber.

    No truss rods.
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    Re: Truss rod and carbon fiber.

    (1). Iirc, the Gore & Gilet book reported a calculated result for guitar necks that two parallel 1/8"x3/8" CF bars set deep enough in the neck to be well below the neutral axis only increased the...
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    Re: Effect of bridge breakover angle.

    If you draw a vector diagram of the forces, you will see that the down force on the top is nowhere near the full string tension. The formula for the down force of the strings on the bridge/top plate...
  17. Thread: Action!

    by Dave Cohen
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    Re: Action!

    The StewMac and D'Addario gauges have graduations in 0.010" (= ten thousandths of an inch). The smallest graduations that I have seen typically available on rulers are 0.032" (= one thirty seconds...
  18. Thread: Action!

    by Dave Cohen
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    Re: Action!

    StewMac has a string height gauge for ~$25 or so. D'Addario has one for about half that. They are simple, useful, and handy little things. They can't tell you something that your hands don't, but...
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    Re: RH vs wood moisture content.

    If your hygrometer doesn't have a calibration function, you can still deFacto calibrate it. Do a google or duckduckgo or bing search for hygrometer calibration methods. Most online sites will...
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    Re: RH vs wood moisture content.

    One question: Have you ever calibrated your hygrometer?
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    Re: RH vs wood moisture content.

    In general, the biggest problems arise when instruments are built at a higher EMC, then sent to a location where the RH is much lower. For instance, free guitar tops and/or back plates can shrink...
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    Re: Book suggestion?

    Update: I couldn't find the Meyer work at MARL, although there is a lot of other useful information there. Then went to the website of the Royal Swedish Academy of Music. Comes up in Swedish, but...
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    Re: Book suggestion?

    Try MARL (Musical Acoustics Research Library) at Stanford. Free, Iirc.
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    Re: Book suggestion?

    Not a book suggestion, but a reference to the paper(s) that Sunburst mentioned:

    (1). Meyer, J.; Quality apects of the guitar tone. In "Function, Construction, and Quality of the Guitar" (E.V....
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    Re: need advide on raising action

    First, your description of fretting the string at the 1st fret and measuring the height of the strings at the 2nd fret is giving you information about the effect of the saddle height, NOT the nut...
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