Posted on June 6, 2024January 17, 2025 by Dale Phillips Questions: 17″ Scale Length String Questions: 17" Scale Length String by R.M. Mottola Originally published in American Lutherie #87, 2006 Rob E. of Lexington, MA asks: Does anyone know of a string that can be put on a 17" scale length instrument, with an after length to the tailpiece of about 6", that is strong enough to reach a mandolin E tuning without breaking? “Questions” editor R.M. Mottola answers: A string with a small enough diameter to be tuned to this pitch at this scale length will have a breaking tension that is too close to its static tension to be of much practical use. When specifying the scale length for a new type of instrument, use a length similar to that used by existing designs with the same pitch range. For high-pitched instruments with long scales (such as the instrument in question) the issue is finding a string with high enough breaking tension to be useful. Unfortunately there are no simple solutions short of having strings custom-made of high-tensile-strength materials. For low-pitched instruments with short scale lengths the issues are tone and, for fretted instruments, intonation. Short, fat bass strings don’t behave much like ideal strings and their partials tend to skew way sharp as they are further shortened by fretting. There is a mathematical relationship among scale length, pitch, tension, and mass per unit length of a vibrating string. Download the paper entitled “Catalog Supplement / String Tension Specifications” from the D’Addario website. The paper (in PDF format) can be found at www.daddariostrings.com/Resources/JDCDAD/images/tension_chart.pdf. It contains comprehensive info on the string formulae as well as mass-per-unit-length (unit weight) data for every string D’Addario makes. Unfortunately, breaking strength data is not available in this paper as the issue of specifying the tension at which a real string will break is more complicated than it might appear. Tensile strength data is available from wire manufacturers but the best bet is to design high-pitched instruments using short enough scale lengths.
