The Making of

THE RIDGEWING GUITAR

- Essays from the Edge of Guitar Evolution -

By

Timothy P. White

New Boston, NH

December 2019

Guitar Evolution

Guitars first appear in the historical record as stone carvings some 3500 years ago and were already highly evolved for both beauty and function. Since then guitars have continued to evolve at a rapid pace, both structurally and tonally, as new materials and technologies have been discovered. Many of today’s most popular “standard” guitars shapes and functions would have been unrecognizable just two hundred years ago. In an evolutionary process, older, once-traditional forms have faded into the shadows as they have been superseded by newer designs. Constantly feeding the guitar market, new design and fabrication technologies hiss and bubble in the hands and minds of guitar alchemists and technologists, causing design innovations to appear, sometimes incremental in nature, and others more radical.

Over time, most innovations fade from popularity, but some stick. What we now call traditional forms, such as the “dreadnaught”, the jazz guitar or the modern classical guitar, were once considered radically large, made possible by string technology allowing for greater tension in the service of loudness. Greater tension also facilitated the production of higher harmonics in the frequency range where we perceive emotion, pain and fear, giving the player additional powers of emotional expression to help lock in the attention of listeners. Electric amplification came along to allow boosting of the higher harmonics even further and louder, making audiences literally go wild. Something deep in the brainstem was being touched. Physical pain now sets the limit of how loudly electric guitars can be played. The rapid evolution of signal-processing technology has broken the shackles off what a guitar can be made to sound like and how it can be played.

So what is left to experiment with? Some ninety percent of beginning guitarists quit permanently within one year, so there is obviously room for improvement.

The Ridgewing Guitar - New Design Properties

The Ridgewing guitar is an experiment in the structural re-organization of the guitar, making it hyper-modular, which results in some remarkable new design properties so that it can now:

1. Exhibit traditional assembled shape, weight, full size and full scale – modeled on Gibson Les Paul.

2. Enable instantaneous knock-down of the assembled guitar to the minimum physically achievable volume form factor for transport, approximately the same as a violin case.

3. Enable instantaneous reassembly of the instrument to pitch.

4. Basic instrument modular components are fully and instantly interchangeable, so for example, a new neck may be attached and put up to pitch in seconds for evaluation. Same goes for the bridge and headstock.

5. All electronics are in the bridge, so completely new electronics can be interchanged via the interchangeable bridge.

6. The basic bridge circuit board can have stacked “buddy boards” readily attached adding novel electronic properties.

7. The body can have instantly attached new functional layers, for example such as an LED light show, built-in sound system, or hard shell back, attached to the back in stacked formation.

Guitar alchemists, pull up your socks!

This writer sometimes get asked why the Ridgewing guitar is described as an “acoustic-electric” when it seems to require being plugged in. The answer is that the Ridgewing guitar, originally called the Chrysalis guitar, started out as a pure acoustic instrument, the original prototype shown here in the Boston Museum of Fine Art’s permanent musical instrument collection. The body consists of a Mylar balloon held against the back of the grillwork face by a fabric cover, having a shape reminiscent of an Ovation guitar. In the lower right corner of this MFA web page, you can follow a link to hear a high-quality pure-acoustic studio recording of the Chrysalis guitar made by the MFA for archival purposes. I think you will agree that it sounds pretty good.

Here is the back story:

Working as a journeyman luthier is a solitary affair. Between the occasional phone call and less frequent customer visit, there is a lot of time spent alone on one repetitive task or another, and the mind roams freely. Thoughts swirl around the instrument being worked on, instruments in general, their history, inner workings, the path that led one to this peculiar situation and possible ways to get out of it, the next shop, a better instrument. Thoughts and dreams and more thinking.

After seven years of instrument making and repair, including four years creating the Journal of Guitar Acoustics, this writer found his thoughts returning more and more to the problem of the guitar’s simple bulk and weight.  After having carried a 12-string guitar while hitchhiking thousands of miles, one begins to take the magical tonal qualities of the instrument for granted, while becoming more acutely aware of the very negative physical side of the guitar’s character. The thing is a pain to carry around and store, even though it is made mostly of air.

One obvious solution is to simply shrink the guitar – the “Backpacker Guitar” solution. Unfortunately, the resulting tonal quality is generally lacking. Somehow the full size had to be maintained. So a thought experiment began to take shape.  How could a full-sized (acoustic) guitar be minimized to its barest physical essence, without being made to sound like a tin can?

If most of a guitar were air, and if this air could somehow be removed at will, not much guitar would be left to carry around. So what kinds of things can have the air removed from then. The answer is inflatable things. God, could it be possible….

The study of psycho-acoustics reveals that the psychological bulk of what we perceive as guitar tonal quality, which is conveyed by high frequencies above 1000 Hz, is radiated off the face of a guitar like heat from a skillet. Further, blocking the sound hole has relatively little effect on the tone of a guitar, particularly for a 12-string.  So, to a first approximation, all you really need is a face, and can get by passably without a sound hole. Could a guitar soundboard be a membrane? Could a membrane as a soundboard?

Observe the face of someone surprised by a tormenter holding a balloon close to their ear from behind and suddenly “squeaking” it. Instantly, the victim’s shoulders tense, teeth are bared, the eyes closed reflexively, and the hands clench into fists as they are raised to protect he face. This is a primal reflex – formed deep in the evolution past and emanating from just above the spinal cord – a flash response to imminent physical attack.  If an inflated membrane can evoke such a strong emotional response in the human psyche, could a guitar somehow be built from a membrane, supported perhaps by a grillwork to achieve acoustical similarity with a wooden sound board? Such a thing could be made to fold, and shrink, and become very light.

Where could this lead?  How far could this thought experiment go?”

Pretty far as it turned out, ending up violating just about every traditional assumption about the guitar’s appearance, form and function.

Though the Chrysalis guitar worked well acoustically and mechanically as hoped and looked pretty interesting as well, most guitarists simply couldn’t get their head around it. “OK – breaks down for transport, I get that, but inflatable”?? The most common coping mechanism was to ridicule the instrument, and it became known as the “inflatable guitar”, failing as a commercial product for obvious reasons. About fifteen carbon-fiber Chrysalis guitars were sold between 2000 and 2002, and then the project went dormant. Working with carbon fiber is an expensive and nasty business, though the result is quite beautiful.

In January 2013, a group of MIT business school students approached me asking if they could use the Chrysalis guitar as the subject of a class assignment to do a market study and write a business plan for launching a potentially transformative “fringe” technology.  Naturally I said "Hell Yes!", and began the non-trivial process of re-imagining and re-designing the Chrysalis guitar as an electric. The first prototype of the new design was completed in December 2014, re-named and re-launched as the "Ridgewing Guitar". Over the next year a number of Ridgewing prototypes were built incorporating different design details.

The Dragonfly

When the Ridgewing/Chrysalis grills were first being imagined, a major unknown was what the basic pattern should be.  How thick should the tendrils be? What should be their spacing? Should all the tendrils be the same thickness, or be of different sizes? Continuous cross-sections or tapered?

The basic task of a guitar soundboard is to push against air and compress it to create sound waves. Guitar soundboard wood and structure have evolved through experiment over the millennia to have the greatest stiffness to weight ratio, which turns out to be a thin veneer of light wood like spruce or cedar supported by an array of stress-bearing braces. It seemed reasonable to assume that biological solutions to flight structures would be also be driven toward a maximum stiffness-to-weight ratio, though more to minimize biological “cost” than to make sound. It turns out that there are mathematical reasons why a braced membrane can be significantly stiffer than the equivalent amount of material in the form of a slab. For example, this is why houses are built with relatively thin plywood backed by a pattern of spaced perpendicular braces carpenters refer to as “joists” and “rafters”.

A search for biology solutions to the air-compression problem meant looking at the structure of critters’ wings, and in particular insect wings, whose job of pushing and compressing air has evolved for flight rather than making music, but the physical requirements are the same – maximum strength-to-weight ratio. The search quickly converged on the wing of the common dragonfly. A dragonfly is a nimble aerial predator, and its wings are a masterpiece of evolutionary engineering which have changed little in basic form since appearing in the fossil record some 325 million years ago. Such continuity of form over evolutionary time scales is unusual, and is the signature of a structure having reached an “optimum” form. (An interesting and slightly horrifying side-note - when dragonflies first appeared 325 million years ago, the earth’s atmosphere contained significantly higher levels of oxygen than today, and dragonflies grew to the size of crows, with 75 cm (30 inch) wingspan.

This wing came from a fairly small dragonfly found expired on the lid of my home aquarium. I scanned it with my flatbed scanner at a resolution of 7200 dpi, so the detail is quite clear. When a dragonfly’s wings unfold immediately after it emerges from its pupa, the tendrils in the crumpled-up wings consist of hollow tubes all joined together. To expand the wings to their final form, the dragonfly injects a protein goo into each wing’s network of empty tendril tubes until they are all fully “inflated”, after which the protein goo dries and hardens and yields an extraordinarily light and stiff structure.

Looking closely at the wing’s structure, one can see that the ratio of tendril width to hole diameter is in the range of 1:5 to 1:10, with tendril thickness changing according to the lines of mechanical stress. This basic mathematical structure of the dragonfly wing seemed as good a guide to designing an “optimum” grill-membrane guitar soundboard as any other, leading to the eventual Ridgewing/Chrysalis grill designs. The Ridgewing re-design of the original Chrysalis guitar body provides backward compatibility with the original Chrysalis carbon-fiber grills.