Official Luthiers Forum!

A question for you experienced builders. Do you decide prior to beginning your build what gauge strings the instrument will be built for? I'm thinking light verses mediums. Do you have a formula for top plate thickness, brace size and position? Does scale length matter? Does a light weight build factor into the equation? I would appreciate your thinking.

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Brad Hall
Mystic Dawg Guitars

1) Yes
2) No but thicker for heavier strings, it's more a stiffness as gleaned by deflection testing than a thickness number.
3) No to scale length in the big picture, it may matter to some, not to me.
4) Yes I am from the school of lack of thought... that just like high performance tone arms for turntables, Ferrari monocots, Lance Armstrong's bike, and Kevlar canoes mass is a critical element to consider with a musical instrument. We have a finite amount of energy resulting from specific strings that has to drive that mass.

Mind you that's my take but YMMV and others are not as keen as I am to build or appreciate very light weight instruments. I could even turn around my own frequent argument for serviceability on my penchant for light weight instruments claiming that a 6 pound dr*ad may require less servicing in time than a 4 pound one. But I like light weight stuff.

A guitar like it or not is a "system" where all things come into play to make or break the experience.

Back to strings - if you build to gift or sell you should consider that the thing will be out of your control and as such it's a good idea to build for lights or mediums. Compromises are just that and like the enduro motorcycle that I had as a kid that could be ridden off road or on and sucked at either sometimes having to build for an unknown final steward can also include some compromises.

Good questions by the way Brad!

Scale length definitely matters in my opinion. If all else is equal, changing the scale length will change the tension of the strings

Technically correct but the change of an isolated scale length change in tension is mouse nuts unless one is building way too close to the edge. Most builders will build, f*ctories too, for either mediums or lights in any common scale length.

By far the largest variable is going from 12's to 13's which can easily exceed a 10% increase in resulting and forever over time.... tension.

When I start building a guitar I pretty much know the player (often me) and how its going to be played, which factors into all of the design parameters. For example, I play in altered tunings and a lot of slide - I'm always thinking about how much tension I want for these and that often means higher gauge strings and longer scales. If I know the player will mostly be doing fingerstyle I try to choose parameters that will make the guitar light and responsive, that includes string gauges. If I know she has a heavy strumming style I might make the guitar a little beefier and use mediums.

I also build a lot of "odd ball" guitars - long scale designed for radical down tuning, resonators, twelve string, Weissenborn style - all of those require special string sets.

As far as I could tell when I researched this was that the difference between tension on twelves on 24.75 scale and thirteens on 24.75 scale is roughly equal to the difference in tension between 24.75 and 25.5 scale lengths with the same strings. Ie. Scale length is as important as string gauge. Although I was messing about with tuning down a semitone as well so I may be completely confused. ..