Graphite-Epoxy Acoustic Guitar Technology

Abstract

We have successfully developed an acoustic guitar (Figure 1) composed of graphite. Trademarked the RainSong® graphite guitar, this instrument uses no endangered tropical tonewoods. The instrument's sound quality is equal to that of a fine wooden guitar. At high frequencies, the clarity, sustain, and play-ability surpasses that of wooden guitars. Because of its construction, the instrument is sturdy and is impervious to humidity, heat, and water.The development of this guitar required analysis of the theory of anisotropic sound propagation in the guitar soundboard and body, and resulted in two patents. We designed prototype guitars in collaboration with Pimentel & Sons, Guitar Makers, and used combinations of unidirectional and woven graphite and aramid fibers in an epoxy-resin matrix.The goal of our project was to accurately duplicate—panel by panel—the acoustic properties of a fine wooden guitar. We had the resulting acoustic modes and frequencies verified in the laboratory. We then developed and constructed open-mold and resin-transfer molding tooling for a family of classical, steel-string acoustic and hollow-body electric guitars, which are now in commercial production.Possibly the first all-composite acoustic guitar, the RainSong® represents a fundamental change in stringed-instrument construction, perhaps the first since the 17th Century Italian masters.The RainSong® technology allows musicians to skirt the effects of climate and transport damage on their instruments. The instrument contains essentially no wood, and hence negates environmental concerns about rapid depletion of the virgin-forest woods, from which stringed instruments have traditionally been made.