250 Million Years of Design Evolution - From Strange to Beautiful
Overview
The Chrysalis guitar started out as an acoustics experiment. The original goal was to find out the minimum volume that a full-size acoustic guitar could be disassembled to, with a design that allowed easy and instantaneous re-constitution of the instrument. The eventual result, based on an inflatable body, was technically successful, but the notion of an "inflatable guitar" was just too strange to be taken seriously. In the end, it was eventually realized that, when the whole "inflatable" feature were stripped away, what was left was an extraordinary chameleon-like electric/acoustic guitar with some rather remarkable properties.
The series of experiments over 30 years leading up to the modern Chrysalis guitar are shown here:
Overview
The Chrysalis guitar started out as an acoustics experiment. The original goal was to find out the minimum volume that a full-size acoustic guitar could be disassembled to, with a design that allowed easy and instantaneous re-constitution of the instrument. The eventual result, based on an inflatable body, was technically successful, but the notion of an "inflatable guitar" was just too strange to be taken seriously. In the end, it was eventually realized that, when the whole "inflatable" feature were stripped away, what was left was an extraordinary chameleon-like electric/acoustic guitar with some rather remarkable properties.
The series of experiments over 30 years leading up to the modern Chrysalis guitar are shown here:
Black 12 - The original experiment
Black 12 - The original experiment was to modify a standard acoustic guitar so that it lacked a soundhole, and the wooden face was replaced by a carbon fiber grillwork enclosing an inflated balloon. A traditional 12-string acoustic guitar was sacrificed for the experiment in the fall of 1981. The grillwork was built up on a wax paper surface using a "drip-castle" technique, where strands of graphite fiber were dipped in slow-set epoxy and draped about on wax paper in a pattern matching the outline of the original guitar.
A major issue was what to use for a balloon. At the time, modern Mylar balloons did not yet exist. A latex weather balloon held air, but popped too easily. A Mylar shopping bag had the right strength, but did not hold air well. The solution was to put a weather balloon inside a mylar shopping bag, which were stuffed together under the grill.
For all its crudity, when the balloon was inflated tight against the grill and the guitar was played, the acoustical result was quite astonishing. From this monstrosity emerged a breathtakingly brilliant tone, significantly louder than the original instrument. The inexplicable success of this first experiment with a grill-membrane soundboard served as a beacon through all the travails that followed.
A major issue was what to use for a balloon. At the time, modern Mylar balloons did not yet exist. A latex weather balloon held air, but popped too easily. A Mylar shopping bag had the right strength, but did not hold air well. The solution was to put a weather balloon inside a mylar shopping bag, which were stuffed together under the grill.
For all its crudity, when the balloon was inflated tight against the grill and the guitar was played, the acoustical result was quite astonishing. From this monstrosity emerged a breathtakingly brilliant tone, significantly louder than the original instrument. The inexplicable success of this first experiment with a grill-membrane soundboard served as a beacon through all the travails that followed.
Big Ugly - The original inflatable guitar, December 1982.
Big Ugly - The original Chrysalis guitar, December 1982.
Built on a $500 bet, the original Chrysalis guitar was a disaster. With a leather body, the instrument was extraordinarily heavy. The bridge was mounted tightly to the center frame like on an electric guitar, so was unable to vibrate freely to make sound. The neck was made of hard maple with difficult-to-manipulate metal fittings. All in all, the thing weighed about a ton and sounded terrible. The only positive features were that 1) the grill looked cool, 2) it bounced like a basketball, and 3) it collapsed for packing, though tools and a bit of time were required. Not knowing how to go forward from this failure, the project was shelved.
Over the next 15 years, from 1982 to 1997, the modern Chrysalis design slowly took form in an on-going thought experiment. The stunning acoustical performance of the original "Black 12" grill-topped guitar had to be able to be reproduced. The grillwork had to be free to vibrate like in an acoustical guitar. The mechanical stress from the strings had to be handled. The mechanical design of the instrument had to dis-assemble and re-assemble instantly and effortlessly. The finished instrument had to be light and beautiful.
Years went by, lost in thought.
Built on a $500 bet, the original Chrysalis guitar was a disaster. With a leather body, the instrument was extraordinarily heavy. The bridge was mounted tightly to the center frame like on an electric guitar, so was unable to vibrate freely to make sound. The neck was made of hard maple with difficult-to-manipulate metal fittings. All in all, the thing weighed about a ton and sounded terrible. The only positive features were that 1) the grill looked cool, 2) it bounced like a basketball, and 3) it collapsed for packing, though tools and a bit of time were required. Not knowing how to go forward from this failure, the project was shelved.
Over the next 15 years, from 1982 to 1997, the modern Chrysalis design slowly took form in an on-going thought experiment. The stunning acoustical performance of the original "Black 12" grill-topped guitar had to be able to be reproduced. The grillwork had to be free to vibrate like in an acoustical guitar. The mechanical stress from the strings had to be handled. The mechanical design of the instrument had to dis-assemble and re-assemble instantly and effortlessly. The finished instrument had to be light and beautiful.
Years went by, lost in thought.
The Box - A handmade guitar in under two hours.
The Box - Mechanical solutions to allow a guitar to be put together and taken apart easily were developed, however it was completely unknown what the optimum mechanical structure of a soundboard grillwork should be that would support the string tension, yet "flutter" like the face of an acoustical guitar. Making an educated guess on how to proportion a grill for good sound production, a flat rectangular aluminum grillwork was machined from a flat plate and fastened to a simple pine box made of 1 x 4's with an old 6-string guitar neck attached. The open back of the box allowed different types of inflatable devices to be put in to test their acoustical performance. The aluminum grill turned out to be a good guess, being very close to the stiffness of an unbraced piece of spruce soundboard. The addition of some spruce bracing reduced the distortion from string tension to an acceptable level . When the box was filled with a Mylar balloon inflated against the aluminum grillwork, the extraordinary tone of the original grillwork-topped experiment was reproduced. This prototype provided a crucial data point on how to design the basic grillwork to roughly match a traditional guitar soundboard structure. It also showed us how the grill material really determines the sound. This prototype was very loud. When I first heard it I thought "It growls!".
Designing the Grillwork
The Chrysalis guitar began to take shape in 1998 using Pro-Engineer CAD design software. A 16" wide body was created roughly along the lines of the Gibson Les Paul. It was important that the finished instrument be full-size with a full string scale length.
The pattern that ultimately emerged for the grillwork was a combination of a heavier structural pattern designed to manage the string tension, and a more whimsical "fine" pattern incorporating biological and wave patterned themes. The final result was intended to have a structural resemblance to a dragonfly wing. The thought was that, since the purpose of a grillwork soundboard was to be the optimum minimal structure move air, in this case to make musical sounds, the 350 million-year old design of the dragonfly wing served as a good model.
The pattern that ultimately emerged for the grillwork was a combination of a heavier structural pattern designed to manage the string tension, and a more whimsical "fine" pattern incorporating biological and wave patterned themes. The final result was intended to have a structural resemblance to a dragonfly wing. The thought was that, since the purpose of a grillwork soundboard was to be the optimum minimal structure move air, in this case to make musical sounds, the 350 million-year old design of the dragonfly wing served as a good model.
Anatomy of the chrysalis Grill Structure
A body design emerged that consisted of two joined "frames", attached to each of which was a grillwork incorporating the heavier structural elements and the lighter acoustically active elements. Of central importance was that the grillwork did not touch the main central member, so that the bridge, when attached to the four hard points on the grills, was free to vibrate as it would on a normal acoustic guitar soundboard. In essence, the idea was to "trick" the bridge into thinking that it was on an acoustical guitar by imbedding it in a vibrationally similar environment.
Here the different parts of the grillwork structure are color coded for clarity. For both grills, the heavier structural elements and fine acoustical elements were merged into a single structure.
Prototype structures were then made from the CAD files, and the Chrysalis guitar started to take form.
Here the different parts of the grillwork structure are color coded for clarity. For both grills, the heavier structural elements and fine acoustical elements were merged into a single structure.
Prototype structures were then made from the CAD files, and the Chrysalis guitar started to take form.
First Light
This image is the first CAD rendering of the Chrysalis guitar. The warped surface of the undulating grillwork is shown red.
The magic of a CAD model is that the imagination is set free to explore any part of it at any magnification from any angle. There is even an "explode" function which spreads all of the parts of the assembly from each other. The eight separate molded components of the Chrysalis guitar could finally be clearly seen.
Making it Real
The first physical realization of the Chrysalis guitar was done with epoxy stereo-lithography. This technology scans the surface of a puddle of light-sensitive epoxy with a precision laser, hardening it. The puddle is deepened by a small fraction of a millimeter, and a new pattern is scanned, bonding to the hardened pattern underneath. After many hours of sequential scanning, the hardened pattern is lifted out of the epoxy bath, and the resulting model is hand-cleaned with an X-acto razor.
The Finished Model
It was an odd feeling to hold a direct physical realization of a dream image that had been developing for almost twenty years.
Unfortunately, the epoxy model was quite fragile and was nowhere near strong enough to subject it to the structural stresses and strains of a functional instrument.
After the euphoria settled down, with part models in hand, the hard work of making real parts began. While the large parts of the Chrysalis guitar were fairly straightforward to create molds for, the grillwork, with its intricate fine channels and the requirement to be made of aligned carbon fiber, stumped even the most experienced mold makers. No injection molding technology existed for this task.
Unfortunately, the epoxy model was quite fragile and was nowhere near strong enough to subject it to the structural stresses and strains of a functional instrument.
After the euphoria settled down, with part models in hand, the hard work of making real parts began. While the large parts of the Chrysalis guitar were fairly straightforward to create molds for, the grillwork, with its intricate fine channels and the requirement to be made of aligned carbon fiber, stumped even the most experienced mold makers. No injection molding technology existed for this task.
Learning to Make Molds
The first step in creating working molds for the grillwork involved first machining exact aluminum models of each grill, which was fantastically expensive, but necessary. It was decided to create silicone molds, as these were the least expensive to make of various mold-making technologies. Even with the final aluminum grill models in hand, which were as rigid as a World War 2 helmet, capturing their precise undulating form in a silicone mold presented an extreme challenge. After a frustrating process of trial and error over many weeks, a multi-step process involving complex jigs, latex sheeting, large amounts of artist's clay and a home vacuum cleaner strained to the utmost finally succeeded in creating useable grill molds. The result was a two-part mold for each grill, where the upper and lower parts nested together precisely.
Molds are complex. In addition to the impression of the part to be made, cavities and channels must be created for "squeeze-out". An array of taper pins around the periphery assure precise alignment of the two mold halves. 260-caliber rifle bullets were found to serve admirably for this task.
Making the Grills - Filling the Molds
Carbon Fiber
It was apparent from the outset of the project that the grills would mimic the mechanical properties of a guitar soundboard if they were made of aligned carbon fiber. Remarkably, obtaining high-quality carbon fiber turned out to be easy and inexpensive, in fact perhaps the easiest part of the entire project. After a bit of online research, a cold-call to a major manufacturer of military-grade carbon fiber was forwarded from the switchboard to Sales, and from Sales to Engineering, and finally to a slightly bemused engineer who happened to be a guitarist in his spare time who, after a good bit of explanation, took an interest in the project. A week later, a large box appeared on the doorstep containing a dozen large spools of glistening shrink-wrapped spools of the highest quality carbon fiber money could buy, in this case for free. I will always be grateful to that unknown engineer.
Epoxy
It was apparent that filling the molds with graphite fiber would take some time, so the epoxy used would have to be slow set. It was decided to use West System epoxy, used in boat-building, as it was readily available in a variety of setup times, and came in convenient container sizes equipped with calibrated pumps, so precise mixtures could be easily obtained. The slowest-setting West System epoxy allowed at most two hours of setup time, which was barely enough to get the molds properly loaded. It was found necessary to pre-chill the molds in a refrigerator, as this had the effect of slowing down the epoxy setting process enough to allow comfortable time for mold-filling.
To fill the mold, strands of carbon fiber were dragged through a puddle of mixed epoxy on a nylon surface, squeegeed out and then laid into the mold. The alignment and density of the fiber layup would determine the strength properties of the finished grill, and so great care had ton be taken to make sure all critical points were properly filled. In addition, any bubbles had to be carefully tamped out. 14-year old Heather White was found to have exceptionally fine skills in laying up graphite in molds.
It was apparent from the outset of the project that the grills would mimic the mechanical properties of a guitar soundboard if they were made of aligned carbon fiber. Remarkably, obtaining high-quality carbon fiber turned out to be easy and inexpensive, in fact perhaps the easiest part of the entire project. After a bit of online research, a cold-call to a major manufacturer of military-grade carbon fiber was forwarded from the switchboard to Sales, and from Sales to Engineering, and finally to a slightly bemused engineer who happened to be a guitarist in his spare time who, after a good bit of explanation, took an interest in the project. A week later, a large box appeared on the doorstep containing a dozen large spools of glistening shrink-wrapped spools of the highest quality carbon fiber money could buy, in this case for free. I will always be grateful to that unknown engineer.
Epoxy
It was apparent that filling the molds with graphite fiber would take some time, so the epoxy used would have to be slow set. It was decided to use West System epoxy, used in boat-building, as it was readily available in a variety of setup times, and came in convenient container sizes equipped with calibrated pumps, so precise mixtures could be easily obtained. The slowest-setting West System epoxy allowed at most two hours of setup time, which was barely enough to get the molds properly loaded. It was found necessary to pre-chill the molds in a refrigerator, as this had the effect of slowing down the epoxy setting process enough to allow comfortable time for mold-filling.
To fill the mold, strands of carbon fiber were dragged through a puddle of mixed epoxy on a nylon surface, squeegeed out and then laid into the mold. The alignment and density of the fiber layup would determine the strength properties of the finished grill, and so great care had ton be taken to make sure all critical points were properly filled. In addition, any bubbles had to be carefully tamped out. 14-year old Heather White was found to have exceptionally fine skills in laying up graphite in molds.
Once the mold halves were fillled, a final half-cup of epoxy was poured into the mold for good measure to fill any remaining voids, and the mold halves were clamped together with a dozen or so cam clamps of the type used in regular guitar making, exerting in total approximately a ton of pressure. An array of plastic tubes built into the mold cavities allowed excess epoxy to ooze out so the two halves could join precisely together. The alignment was further facilitated by a "blistering" effect achieved when the molds were made, where the regions between the grill elements bulged outward into a corresponding concavity on the opposite mold half.
The mold was filled in mid-afternoon, and then allowed to set overnight. In the morning a blast of compressed air into a vent in the mold forced the two halves apart, and a finished grill was revealed.
The mold was filled in mid-afternoon, and then allowed to set overnight. In the morning a blast of compressed air into a vent in the mold forced the two halves apart, and a finished grill was revealed.
Below are shown the original machined aluminum master for the treble grill (blue, at top), and the first set of prototype grills, showing different amounts of graphite filling. It was eventually found that all grillwork had to be carbon fiber-filled for adequate strength.
Grills could be made at a maximum rate of one per day, including several hours of clean-up with a razor and file to remove "flash". The results made it worthwhile.
Grills could be made at a maximum rate of one per day, including several hours of clean-up with a razor and file to remove "flash". The results made it worthwhile.
As luck would have it, the grills turned out to have very nearly exactly the hoped-for structural strength and light weight. Once the problem of grill fabrication was solved, the Chrysalis guitar could finally be built.
Using rapid-prototyped masters from the CAD design, silicone molds were made for the frames, headstock, headstock lever, bridge and neck. Hand-machined metal fastening mechanisms were added to the various parts to allow them to fit together precisely.
A little gold spray paint on the grills, and ....
Using rapid-prototyped masters from the CAD design, silicone molds were made for the frames, headstock, headstock lever, bridge and neck. Hand-machined metal fastening mechanisms were added to the various parts to allow them to fit together precisely.
A little gold spray paint on the grills, and ....
