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Length of Newt’s Tail by Width of Dragon’s Hair

Length of Newt’s Tail by Width of Dragon’s Hair

by Ken Sribnick

Originally published in American Lutherie #55, 1998



Don’t hurt me. I’m going to tell you an old joke. How many luthiers does it take to split a dragon’s hair? One to split the hair, and the rest to say, “Oh, that’s how you do it.” At our 1995 convention, I heard a number of luthiers ask about measurement and precision: How do you check this? When is that flat enough? In the spirit of the little joke, I thought it might be interesting to tell you my approach. These surely aren’t the only, or necessarily the best, methods — only how one man splits dragon hair and newt’s tail in our little shop.

My early lutherie and repair went slowly until an experienced luthier, a repairman in New York’s music district, helped me along. His “luthier’s gold” included explaining which measuring tools to have, and how to use them. Consistency is essential. You must strive to reduce error and deviation. To this end I have “master” reference tools in the shop: one ruler, one caliper, one flat surface, and my drawings. It doesn't matter if you use metric measurements or inches. Just pick the system you’re comfortable with, have good master references, and, stick with them. You’ll be successful. I’m metric because I tune Toyotas as well as 12-strings.

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The Metaphysics of the Guitar

The Metaphysics of the Guitar

or Some Thoughts on the Differences Between Handmade and Factorymade

by Ervin Somogyi

Originally published in American Lutherie #85, 2006



It may seem strange to some readers to find an article touching on metaphysics in a magazine on guitar making; it will also seem perfectly appropriate to others that such a topic be included. The metaphysics of the guitar has to do with “that extra something” that’s intangible and possibly even indefinable. Some guitars have it. Some don’t. It is variously called “the magic,” “the soul,” “the allure,” and so on, even though these terms can be elastic and elusive. None of this is exactly news to anyone who knows the guitar.

I’ve thought about this. It seems to me that there are at least two components to “the magic.” The first one has to do with whether a guitar has sufficient “extra oomph” (by whatever standard one wishes to define it: tone, warmth, exquisiteness, subtlety, etc.) to warrant one’s falling in love with it. No mystery in this. This happens at the level of performance/attributes that can eventually be discerned and identified, even if at first the instrument seems magically beyond words. It really isn’t: the words can/will sooner or later be found.

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Calculating Fret Intervals with Spreadsheet Software

Calculating Fret Intervals with Spreadsheet Software

by Wayne Kelly

Originally published in American Lutherie #43, 1994



Luthiers who own or have access to a personal computer will find spreadsheet software useful in calculating fret intervals. Spreadsheet software is commonly used for accounting, budgeting, and presentation of tabular data. It is invaluable for testing “what if” scenarios because a change made to one cell of a spreadsheet will cause a “ripple effect,” automatically changing values in other cells dependent on that cell. This feature of spreadsheet software makes it possible to calculate fret intervals for a given scale length instantly. Change the scale length value and “presto,” another set of fret intervals is automatically and instantly calculated and displayed. Results can be printed if desired. Within a few minutes one could create a book of fret interval tables for dozens of different scale lengths.

I created a spreadsheet to calculate fret intervals using the “fret factors” found in a popular textbook on guitar building (Cumpiano, William R. and Natelson, Jonathan D., Guitarmaking: Tradition and Technology, Rosewood Press, Maine, 1987, p. 268). With fret factors, each fret’s distance from the nut is determined by simply multiplying the fret’s factor by the chosen scale length. My spreadsheet allows one to enter a given scale length, expressed in decimal inches, and it then calculates and displays the distance from the nut to each of 21 frets, as shown in the accompanying figure. The fret intervals are displayed in three columns expressed in centimeters, decimal inches, and sixty-fourths of an inch, respectively.

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Derivation of Formula for High Point of Back

Derivation of Formula for High Point of Back

by Jon Sevy

Originally published in American Lutherie #75, 2003 and Big Red Book of American Lutherie Volume Seven, 2015



Quantities:
S = height of guitar sides at neck block
B = height of guitar sides at end block
E = B - S (difference in height at shoulders and butt)
L = length of guitar body
A = length of body measured at angle (see diagram)
D = deflection in arched back (see diagram)
R = radius of back arch

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Calculating Guitar Side Height

Calculating Guitar Side Height

by Mike Doolin

Originally published in American Lutherie #75, 2003 and Big Red Book of American Lutherie Volume Seven, 2015



Back in American Lutherie #58 (Big Red Book of American Lutherie Volume Five), Jon Sevy published the article “Calculating Arc Parameters” which described how to calculate the radius, length, or depth of a curve. I’ve used these formulae extensively ever since for radiusing fretboards, making dished workboards, calculating neck angles, and even nonlutherie shop tasks. Recently it occurred to me that one could use them to calculate the height of a guitar’s side at any point. If the guitar has a spherically domed back, the back falls off from its highest point in an arc in every direction, as in the photo.

This “high point” is effectively the North Pole of the sphere from which the back arch is taken. If we assume a top whose perimeter is all in the same plane, as in Fig. 1, that plane intersects a line of latitude on that sphere. The high point is therefore the point on the back which is farthest from the plane of the top perimeter. All measurements of side height are then distances between that plane and the surface of the sphere of the back arch. I adapted Jon’s formula to calculate the falloff from the high point on the back to any point on the side:

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