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A Method for the Design of the Guitar Body Outline

A Method for the Design of the Guitar Body Outline

by R.M. Mottola

Originally published in American Lutherie #97, 2009



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



One of the most tedious and time consuming aspects of designing a new guitar for me is the process of designing the body outline. The body outlines of my early instruments were the results of many hours of labor, usually over the course of many weeks. This process was so time consuming that I would often forgo it entirely, opting to reuse an existing body outline as is, or scaling up a guitar outline for use in an acoustic bass guitar. But over the years I’ve settled into a method for guitar body outline design which is far less tedious and consumes far less time than did my original efforts. This method involves the use of a standard model of the guitar outline. Use of this standard model helps to make the process of developing an outline more standard as well, and this in turn has resulted in the development of techniques which save time and frustration.

In this article I will be outlining the model and discussing some common guitar body types in the context of this model. In talking about the design method which makes use of the model, I’ll try to touch on some of the generic qualities of guitar body outlines and how they can be quantified in terms of the model. Finally, some of the tools and techniques of the method will be detailed. Please note that what I am discussing here is only the mechanical aspects of a body design. Issues of acoustics or ergonomics are not covered. Also note that this method works equally well with either pencil and paper or CAD drawing tools, although there are some differences in how these tools are used.

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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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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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A Method For the Design Of the Guitar Body Outline Part 3: Compound Radius Curves

A Method For the Design Of the Guitar Body Outline Part 3: Compound Radius Curves

by R.M. Mottola

Originally published in American Lutherie #103, 2010



See also,
A Method for the Design of the Guitar Body Outline by R.M. Mottola
Parametric Models of Guitar Cutaways by R.M. Mottola



The article “A Method for the Design of the Guitar Body Outline” in AL#97 presented a model for drawing guitar body outline halves based on five circular arcs and three straight line segments, as shown in Fig. 1. Here I will present an enhancement to that model. As the original article pointed out, the five-arc model can be used to draw most but not all guitar body outlines. So it was probably inevitable that the first feedback I received following the publication of that article was from someone trying to draw an outline for one of the instruments for which this model is not ideally suited. There are a couple of common instruments that have outlines which cannot be drawn using this simple five-arc, three-straight-line-segment model. These instruments, the OM and the Maccaferri-style guitars, have a “dropped hips” look to the lower bout that cannot be approximated by a single circular arc (Fig. 2).

Fortunately, the lower bouts of these guitars can be accurately drawn with a simple enhancement to the model. The enhancement replaces the single-arc lower bout curve with a compound-radius curve. A compound-radius curve is composed of a series of circular arcs, each tangent to the one succeeding it. Although all manner of complex curves can be built up in this fashion, for the purpose of enhancing the simple guitar body outline model, we really only need to introduce compound-radius curves of two radii.

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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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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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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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Our Great Spherical Friend, Part Two

Our Great Spherical Friend, Part Two

by Frederick C. Lyman, Jr.

Originally published in American Lutherie #7, 1986 and Big Red Book of American Lutherie Volume One, 2000

See also,
Our Great Spherical Friend, Part One 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.



Our intent, in the design of a musical instrument, should be to keep in mind this theoretical correspondence between the atmosphere and the instrument, and to realize it in as much detail as possible. The objective is the possibility of the highest degree of control of the final tone production, with a minimum amount of effort and anguish by the performer.

Music differs from other atmospheric sounds. The tones are related to emotions and are arranged in such a way as to project a panoply of emotional changes and thereby tell a story or take the listener on a sort of emotional trip. The success of a musical instrument lies in the extent to which it can be made to facilitate this kind of expression.

However, the instrument is first and foremost a physical device, and its expressive properties are supported by its acoustical properties, which are in turn supported by its structural properties. Because the instrument is in a state of tension, it must have a certain structural strength, adequate to give it a basis of firm tonality.

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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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