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Questions: Amplifying Flattop Bass

Questions: Amplifying Flattop Bass

by Harry Fleishman

Originally published in American Lutherie #65, 2001 and Big Red Book of American Lutherie Volume Six, 2013



Mark Brantley of Appleton, Minnesota asks:

I recently ordered Tim Olsen’s plans for the Flattop Bass (GAL Plan #13). Do you have any advice on a good electric pickup for it?


Harry Fleishman of Boulder, Colorado responds:

It’s difficult to offer too much advice about amplifying your acoustic bass without more input about how loud you need to play, how high a fidelity to the instrument’s actual acoustic voice you want, and what your budget is; but here goes anyway.

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Questions: Guitar Air Cavity

Questions: Guitar Air Cavity

by Art Davis, Al Carruth, and Joe Franklin

Originally published in American Lutherie #63, 2000 and Big Red Book of American Lutherie Volume Six, 2013



Tom Blackshear of San Antonio, Texas asks:

Is there a formula for measuring the air cavity of a guitar box, then figuring out how to keep the same amount of air with slightly different box dimensions?


Art Davis of San Diego, California responds:

Use bird seed. It’s not totally accurate but it’s easy. Pour it in, pour it out, and measure it. Hold the guitar really well because ten or twenty pounds of bird seed is heavy. Also, as per W.D. Allen’s, “Basics of Air Resonances,” in The Big Red Book of American Lutherie Volume 1, changing the air volume doesn’t always do what you think it’s going to.

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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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