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.