The “G” Thang Acoustic Guitar Design Tool

About “G” Thang

By Robert M. Mottola

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 consists 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. An even easier way to design guitar body outlines is to use “G” Thang software, which is available for Windows computers and can be downloaded for free here.

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 uses the five arc, three straight line segment model described above (or optionally a seven arc, three straight line segment model), and provides features so you can iteratively and interactively make changes to your body outline design. The 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. “G” Thang also includes a number of standard guitar and ukulele body outlines, so you can start your own designs from one of these standards if that is the way you want to proceed. Once you are satisfied with your design, you can either export it to CAD or drawing software via a .dxf file, or you can simply read line segment locations right from the “G” Thang window for use in your paper and pencil drawings. The tool also provides complete fretboard layout, including fret locations and dot marker locations, and it also automatically draws a proportionally spaced nut for you.

Downloading “G” Thang

“G” Thang runs on Windows machines that have screen resolution of at least 1024 x 768. The main window is quite large, and higher screen resolution settings are preferred. But it will run on systems with 1024 x 768 resolution if taskbar properties are adjusted. See the documentation with the program for more details on how to do this.

Note to users of Internet Explorer 8: IE8 has known problems with downloading files. If you experience problems downloading “G” Thang with IE8, try this: Instead of left clicking on the download link below, right click on it and then select Save Target As… This will (usually) successfully download the installation file, which can then be run to install “G” Thang.

Download file






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