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Parametric Models of Guitar Cutaways

Parametric Models of Guitar Cutaways

by R.M. Mottola

Originally published in American Lutherie #99, 2009

See also,
A Method for the Design of the Guitar Body Outline by R.M. Mottola
A Method For the Design Of the Guitar Body Outline Part 3: Compound Radius Curves by R.M. Mottola



In the article entitled “A Method for the Design of the Guitar Body Outline” in AL#97, I introduced the concept of parametric models for the design of the guitar body outline. That article addressed symmetrical body outlines only. In this article I want to consider parametric models for the body cutaway. Taken together the two articles demonstrate a complete method for the design of typical guitar body outlines.

Although it was possible to devise a simple parametric model for the design of the symmetrical guitar body outline that was adequate for most of the “standard” guitar body outline types, things are a bit more complicated where the cutaway is concerned. The basic problem is that, except in the most basic designations, cutaway styles have not yet settled out into a small number of distinct types. Rather than pursue a model that would accommodate all existing cutaway designs, I chose instead to derive basic models for the two primary cutaway types, leaving enough configurability to insure that most existing cutaway outlines could at least be approximated.

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Questions: Significance of Q

Questions: Significance of Q

by Brian Burns

Originally published in American Lutherie #86, 2006



John Belluci of Baltimore, MD asks:

Please explain what “Q” is when referring to wood or instruments. The definition I’ve seen is, “internal damping.”


Brian Burns of Fort Bragg, CA responds:

“Q” is one of the basic qualities of the materials we use to make stringed instruments. The traditional low-tech Q test is to listen to the tap tone of a piece of wood and hear how long it takes for the sound to die away. The longer the tap tone lasts, the higher the Q, and the greater the potential of that piece of wood to make a loud instrument with long sustain. The design and construction of the instrument of course determine the ultimate result; the Q test just gives you an idea of the potential of that particular piece of wood.

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Questions: String Tension and Purity of Tone

Questions: String Tension and Purity of Tone

by Alan Carruth

Originally published in American Lutherie #99, 2009

See also, Questions: String Tension and Pure Tone by R.M. Mottola



Alan Carruth from Newport, New Hampshire writes in response to Pat Bowen’s question in AL#98 about the relationship between string tension and purity of tone:

While there is some truth in the equation higher tension=purer tone, it is, as the editor said, not as simple as that. A lot depends on how you get the higher tension.

When you pluck a string, it vibrates at a set of different, but related, frequencies. For ideal strings, the kind that you only find in physics books, these frequencies form a harmonic series; each one is an exact whole-number multiple of the lowest (or fundamental) pitch that the string makes. Real strings don’t do this, and that affects the way they sound.

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Questions: String Tension and Pure Tone

Questions: String Tension and Pure Tone

by R.M. Mottola

Originally published in American Lutherie #98, 2009

See also,
Questions: String Tension and Purity of Tone by Alan Carruth

 

Pat Bowen from the Internet asks:

A generally accepted fact is that the higher the string tension, the more pure the tone. This causes me grief, since I have to build instruments to support the heaviest strings. Even if I don’t recommend them, someone is going to use them. But is this thing about the high tension and pure tone really true or is it just a folk tale?


The Questions Column editor
responds:

The short answer is yes, it is true, and the short explanation is inharmonicity. The higher the tension, the closer the partials are to true harmonic multiples of the fundamental frequency. On p. 115 of his book Engineering the Guitar — Theory and Practice, Richard Mark French states: “...increasing the radius [of the string] or elastic modulus [i.e., stiffness] makes the deviation from the ideal harmonic series worse, while increasing tension or length makes it better.” This is an interesting topic worthy of an article or at least a longer explanation than I’ve given here, which I hope someone will provide.

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Our Great Spherical Friend, Part One

Our Great Spherical Friend, Part One

by Frederick C. Lyman, Jr.

Originally published in American Lutherie #6, 1986 and Big Red Book of American Lutherie Volume One, 2000

See also,
Our Great Spherical Friend, Part Two by Frederick C. Lyman, Jr.
Our Great Spherical Friend, Part Three by Frederick C. Lyman, Jr.
Improving the Plywood Bass by Frederick C. Lyman, Jr.



We are referring to the cloud of gases, still largely beneficent, that surrounds our planet. This immense mass must be immensely and massively frustrated. Because, while it constantly tries to find a state of peaceful repose and equilibrium, it is just as constantly subjected to agitation by forces large and small. The earth whirls beneath it, the sun warms it on one side at a time, various objects in space tug at it, and innumerable minor annoyances are inflicted upon it by the residents of Earth.

By far the worst of the minor offenders are the members of the human race, who should really be more grateful to their spherical friend. Instead, they have craftily discerned that the atmosphere that surrounds them is indeed indefatigable in its effort to reach an equilibrous state. With fiendish zeal they have invented devices for the sole purpose of agitating their friend. Some of these torture implements are known as “musical instruments” and are accorded a special reverence by those who create and use them (some of whom, however perversely, even banding together in special societies to promote these activities).

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