Applying Technology to Building

An Introduction to the  Technology Section of  the Website

      I have finished writing my book “Left-Brain Lutherie: Using Physics and Engineering Concepts for Building Guitar Family Instruments: An Introductory Guide to Their Practical Application”. Details can be found here.
I thought I might step in here a moment and try to clarify my position regarding my website and the nature of the technology “help” that I’m offering to the lutherie community.  Before returning to Hilo, Hawaii in 1991 I was a research scientist for nearly 20 years. I did such work because I like to study the “why” of things and how they work. I have tried to apply the same general way of thinking to my ukulele and guitar making. The website is a way of trying to share ideas with others and in no way is it meant to force others to my way of thinking. I welcome the exchange of ideas and would look forward to cooperative intellectual ventures, although this has rarely happened.

For the nearly 17 years that I have been building and repairing instruments, I have read many articles and books about the building and repair of instruments both from the scientific and non-scientific approach. In general, the non-scientific approach is excellent for the joinery and esthetic portions of building, but I personally have never been able to follow discussions regarding the voicing of an instrument as written by such builders. To me, these voicing descriptions are more or less elegant expositions of an experience rather than a guide to building. One is left with “Well, you just have to do it until you get it”, analogous to “cook until done”. I respect the final product that many such builders produce, but am personally frustrated by my lack of understanding with their approach.

So I and others look at at least a portion of the building of an instrument from a scientific and engineering approach. There are literally thousand’s of mistakes to be made while building. I think that by looking at a stringed instrument in terms of its engineering, many of the mistakes made by beginners can be avoided. For example, how stiff should the neck be for a given string tension? A spreadsheet on the website created by Dr. Josh Gordis and me allows the user to calculate neck deformation under string tension and know if the thickness of the neck and fretboard are sufficient or if a truss rod is also necessary. Would anyone really want to build an instrument where the neck bowed up enough to make the instrument unplayable? I don’t want to think so, but many in the instrument making community seem unfazed by this problem.

Often the open G string on a classical guitar is dead sounding. Generally it’s because that note is co-incident with the first fundamental resonance of the top of the instrument. In order to essentially eliminate the deadness, one needs to adjust the first back resonance to a semitone above or below the top so that the top and back couple. This effect has been known for at least two to three decades in the literature (see articles by Dickens in the Catgut Acoustical Society, Caldersmith in American Lutherie and Journal of Guitar Acoustics and Carruth in American Lutherie) , yet relatively few builders or companies appear to acknowledge the effect or try to adjust for it. I wrote another spreadsheet for the website recently which allows the user to utilize the huge amount of work of Jurgen Meyer (article in Journal of Guitar Acoustics) in this area and determine what resonances will be appropriate. Will the finished instrument be ready for John Williams? Of course that will be determined by many other factors, but we will have done something positive regarding the betterment of the tone of the instrument.

The work of Bartolini and Bartolini ( Chicago Papers in Journal of Guitar Acoustics) is another case where by simple top deflection measurement, one can determine from the measurement of existing successful instruments what stiffness’ work and should be replicated on other instruments. A simple device for making such measurements is described on the website.

No matter what approach is used in making a very good instrument, the process still takes a great deal of time and effort. I further suggest that very good and equally bad instruments have been made by both approaches, so no one has a lock on the “best” way . I feel that the enlightened builder should take those things from each approach which suit his/her style of building, continue to push the envelope for both groups, and share their experiences with the community.