String spacing to edge of fretboard

[journeymanjohn]

On my Johnson MF-370, I have noticed that the spacing on either side of the E and G courses, and the edge of the fretboard are not equal thru out the length of the neck. That is to say, the spacing is equal at the nut, and on the saddle, with the whole bridge seemingly centered between both F holes (by eye, not actually measured). The space between the outermost E string and the edge of the fret/finger board remains constant the total length. The spacing between the outermost G string and the edge of the board widens as it moves away from the nut and towards the body.

I have noticed many mandolins that do this. Actually most every mandolin I have personally held (mostly relatively inexpensive models, although regularly recommended good "starter" mandolins, from what I read hear on the cafe), does this.

So is this a feature that is engineered into mandolins, and if so... for what purpose. Or is this a defect.

I specifically look for this in photos and sometimes I see it.... sometimes I don't.

[sunburst]

...is this a feature that is engineered into mandolins, and if so... for what purpose. Or is this a defect.

It's kind of 'neither one'.
If you sight the strings from tailpiece to nut (you'll have to rotate the mandolin a little) do they center on a straight line or do they break slightly to one side as they cross the bridge? That's not an easy thing to see with some tailpieces because the string spacing can be pretty wonky on some tailpieces, but ideally, the center line of the strings will follow the center line of the mandolin. If the neck set is such that the center line of the neck and the center line of the body are off, the bridge will not sit centered on the body or the strings will not follow the center of the neck. The f-holes can be different distances from center, the strings can be off center on the bridge, the bridge can be pushed slightly to one side, etc.. In short, there can be many reasons that the strings would be off center on the neck, so carefully examining the mandolin is the only way to determine the reason.
The good news is; it doesn't really matter as long as the strings are close enough to center that the mandolin plays fine, and in fact, finding everything to be perfectly centered may well be the exception rather than the rule.
Furthermore, many builders space the strings progressively wider from E to G so the center of the string path can be a line other than the middle of the space between the D and the A. There is generally more space from the edge of the nut to the G than there is from the edge of the nut to the E. That extra space can be preserved for the length of the fingerboard or it can equalize toward the bridge. Sometimes the taper of the fingerboard is not designed for the desired string spacing at the nut. All kinds of things can be at play.

[avaldes]

John, I'm not a builder, but I have wondered if the practice of symmetric string spacing is traditional and aesthetic. Might there be an advantage to deliberately having the strings off center (say, so there is more top surface on the bass side for improved response) or is it the case that the entire top instantaneously resonates over its entire surface in response to string vibration?

[journeymanjohn]

So, if I understand you correctly, Sunburst, ideally one should be able to take a string from center of tailpiece to center of the nut, and it should center on the neck, and bridge. However, as long as it's close enough that the mandolin is playable, all is well.

I would imagine that if one had a radiused board, the centering issue might be more of an issue, as strings may actually get closer to the frets if not running parallel to the radius? Or would this difference be so negligible as to go unnoticed in most cases?

[Pete Jenner]

John, I'm not a builder, but I have wondered if the practice of symmetric string spacing is traditional and aesthetic. Might there be an advantage to deliberately having the strings off center (say, so there is more top surface on the bass side for improved response) or is it the case that the entire top instantaneously resonates over its entire surface in response to string vibration?

Yes, the normal modes of motion of the plates are global - i.e. they occupy the whole plate.There is no acoustic advantage to having strings and fretboards offset one way or the other. See Dave Cohen's work and the many posts by Dave, John, Peter Coombe and others on the subject.

[sunburst]

So, if I understand you correctly, Sunburst, ideally one should be able to take a string from center of tailpiece to center of the nut, and it should center on the neck, and bridge. However, as long as it's close enough that the mandolin is playable, all is well.

I would imagine that if one had a radiused board, the centering issue might be more of an issue, as strings may actually get closer to the frets if not running parallel to the radius? Or would this difference be so negligible as to go unnoticed in most cases?

That pretty much sums it up.
As for the strings tracking slightly diagonally to the radius, that is the main reasoning behind using a conical fingerboard (usually called a "compound radius"); to minimize the departure of the string path from center of the arch.
We normally have a very slight amount of relief in the fingerboard. A range of relief amount is acceptable for best playability, so as long as the amount of relief falls into the acceptable range under all strings, the departure from arch center of the string path results in negligible difference in playability.

[EdHanrahan]

... Furthermore, many builders space the strings progressively wider from E to G so the center of the string path can be a line other than the middle of the space between the D and the A. ...

Some expansion might be helpful. I know that this is common on guitar, to keep the strings equidistant from each other at each string's edge, rather than just keeping their centerlines equal-spaced while their increasing thickness decreases the space between the lower-tuned strings.

On mandolin, I can see the wisdom of keeping the space between each course equal, thus (maybe) providing equal finger-space across the fretboard. What I'm unsure about is the need, if any, to increase the space between the lower-tuned pairs in each course, thus providing more "swing room" for the bass strings to, hopefully, not hit into each other. Or is this not an issue?

[sunburst]

...the need, if any, to increase the space between the lower-tuned pairs in each course, thus providing more "swing room" for the bass strings to, hopefully, not hit into each other. Or is this not an issue?

It can be an issue. I've never encountered the problem on the D strings, but several times I've had customers who regularly had buzzing resulting from the G strings hitting one another. When they are spaced wide enough to prevent that, they are wider than would be prudent for the A and E strings for a couple of reasons. 1) The total string spacing gets wider as the pair spacing gets wider, so spacing all the pairs as wide as the G pair would result in either a nut that is too wide or the space between pairs being too small. 2) when the space between the strings of a pair is too wide they will sometimes "split" beneath the players fingertip, especially players with smaller, well calloused fingertips (often the case with better players).
The best optimization of space for the G strings, narrowness of neck width, and spacing of the A and E pairs is accomplished by using graduated spacing from E to G, both between pairs of strings and between the strings of the pairs.

[Phil Goodson]

Another unrelated reason that I LIKE the OP's string configuration is that I tend to push bass strings off the edge ( especially up the neck) if they're too close to the edge. The E string of course tends to get pushed AWAY from the edge with fretting.