The "G" Thang Acoustic Guitar Design Tool

The starting point for a successful guitar build is a detailed plan. In cases where a plan is not available, the builder will need to make one. This necessary process is both time-consuming and tedious. "G" Thang acoustic guitar design software can make the process of making a plan a lot quicker and a lot easier.

In terms of process, there are two types of activities involved in designing an acoustic guitar (or ukulele or acoustic bass guitar) and making a drawing to build from. The first is simply a matter of translating some numbers into a drawing. The fingerboard is like that. Fret location, dot marker location, the divergence of the sides of the board, these are all described in just a few numbers. But drawing the fingerboard from these numbers though is time-consuming and can be tedious. The second type of design activity is highly iterative. Designing the body outline is a good example of this. It is the kind of thing where you continually refine your work until you've got it just the way you want it. This process can also be tedious, whether drawing on paper or using drawing software.

The "G" Thang guitar design tool is an app that takes a lot of the tedium out of the design of the acoustic guitar and similar instruments. This tool provides complete body outline and body profile design, as well as fretboard layout. The latter includes fret location, dot marker location and the dimensions of a proportionally spaced nut. Also provided are neck profile design, and a whole lot of pre-made sub-assemblies for typical instruments.

Instrument designs made in "G" Thang can be exported and then used by both CAD drawing tools and artistic drawing tools for further design development.

Initial appearance: March 18, 2009
Last updated: January 31, 2024

Getting Started with "G" Thang

"G" Thang is a web app which can be run on any computer with a mouse as its pointer device. To use all of its features, it should be opened and run in a Chromium-based browser, such as Chrome, Edge, and DuckDuckGo. It can be used on the Brave browser but the browser must be configured to allow file saving. Run "G" Thang using the button below.

Run "G" Thang

Once it is up and running, go to the menu bar and check out Help->Documentation for more information. Also see Help->About for terms of use. "G" Thang contains a number of pre-built instrument designs for guitars and ukuleles, and the easiest way to get a feel for what it can do is to load one of those designs and then make some modifications. Go to File->Initialize to see the pre-built designs.

Make a shortcut of the link in the button above. That way you will always be using the latest version of "G" Thang.

"G" Thang Features

  • Provides complete body outline shape design.
  • Visual aids help you design your body outline quickly.
  • Provides complete fretboard drawings from specifications, including drawing frets, dot markers, and strings.
  • Includes a library of pre-designed instruments, so you don't have to start your designs completely from scratch, unless you desire to do so.
  • All panes on the window can be resized by grabbing and moving the pane borders.
  • The graphics pane which contains the drawing can be panned and zoomed.
  • All instrument initializations (built-in designs) include values for all parameters.
  • Designs can be saved to and loaded from the local file system.
  • Designs can be exported as DXF files for use by CAD drawing software.
  • SVG export makes designs available to artistic drawing software.
  • A body scaling function provides scaling the size of the body up or down.
  • Dimensions can be expressed in units of inches, centimeters, or millimeters.
  • Includes menus of some standard fretboard tapers.
  • Includes menus of some standard fret wire profiles.
  • Includes menus of some standard string action profiles.
  • Includes menus of some standard string sets.
  • Provides information about string tension and compensation.
  • "G" Thang calculates top plate area, body volume, and Helmholtz frequency.
  • Includes facilities to build drawings from measurements taken from real instruments.
  • Warns about design issues such as high string tension and instrument dimensions out of standard proportions.

The History of "G" Thang

In American Lutherie #97 I wrote an article about a simple model which can be used to design the outline of an acoustic guitar. The model consisted of five circular arc and three straight line segments for each half of the body. Although quite simple, this model can be used to accurately draw most "standard" guitar body outline shapes as well as a lot of nonstandard ones. The article described how to use the model to draw guitar body outlines, on paper, or using CAD drawing tools. A couple of follow up articles expanded on the basic concept, specifying a more comprehensive model of the outline using seven circular arc segments.

The articles were technical in nature, and required drafting skills to be useful in actual guitar outline design. This demonstrated the need for an even easier way to design guitar body outlines, and "G" Thang was built for just that purpose. "G" Thang is a web app available from this site.

The process of designing a guitar body outline is an iterative one. You take a good guess at what you want the outline to look like, draw it, evaluate your drawing, and then make modifications to it. The process can be tedious when done using CAD drawing software and is even more so if paper and pencil are used.

Some number of years ago, with the aid of another engineer, I developed two interactive scripts for use with an off brand CAD software package that made the process of designing the outline of the acoustic guitar simpler and quicker, and made the process of designing and drawing a fingerboard a simple matter of filling in a form. Although originally intended only as demonstrations of CAD scripting tools, I used these scripts on and off during the intervening years, even though each use required me to re-learn how to use the off brand CAD software. I needed to generate a number of body outlines for the above mentioned American Lutherie article, and this provided the impetus to convert the CAD scripts to a stand alone program.

"G" Thang software "knows" a lot about the proportions of guitar bodies, and provides guidelines and other helpful facilities to make it easy to design your own body outlines. The tool is extremely popular with both professional and amateur instrument designers.

By the way, I would highly recommend getting copies of American Lutherie #97, American Lutherie #99, and American Lutherie #103 and reading the articles on body outline design and cutaway design. These serve as good background documentation for using "G" Thang. Of course, all serious luthiers are members of the Guild of American Luthiers and get American Lutherie as a benefit of membership. You should too!

Downloading Older Versions of "G" Thang

The previous release of "G" Thang was an app which ran on Windows computers only. It can still be downloaded here:

 Download "G" Thang 0.8 installer (7.4 MB .exe)


• Latest American Lutherie article: "Book Review: The Caldersmith Papers", American Lutherie #148 Table of Contents

• Latest research article: "Quantifying Player-Induced Intonation Errors of the Steel String Acoustic Guitar"


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