All this research has prompted some observations, first about what a crossover guitar needs, and secondly about what traditional classical guitarists could learn from the features of a crossover guitar. I expect this to be controversial!
It is my belief that a nut width of 48mm on a nylon-string guitar would be just fine for many guitarists, even those who play classical guitar exclusively. It provides considerably wider string spacing (at 8mm between strings) than what you find on most steel-string guitars. It is noticeably narrower than the 9mm string-to-string spacing you find on a traditional classical guitar with its 52mm nut width. It really does make a difference. If you are not already accustomed to a traditional classical guitar neck, try it; you’ll like it.
At the other end, however, a crossover classical guitar needs to have a string spread of 57 to 60mm at the bridge saddle. This is the traditional classical width, much wider than that found on most steel-string guitars. The reason for this is that if you are playing traditional classical right-hand finger technique (p i m a), you need a lot of space between the strings to dig in and get a good loud sound.
Virtually all traditional classical guitars have a completely flat fingerboard which has no inlays on the fingerboard or on the side. However, virtually all electric and steel-string acoustic guitars have “side dots” that let the player glance down and determine the fret location of his left hand. All classical guitars should have side dots. There is no drawback to this. And if you’re worried about traditional appearance, don’t be. Nobody can see the side dots except the person playing the guitar.
Furthermore, there is no reason that a classical guitar should have a flat fingerboard. This is an unproductive hold-over from the 18th and 19th century when flat fingerboards were the only kind that luthiers made on plucked string instruments. The primary reason for remaining with the flat fingerboard design is one of ease of manufacture and low cost for the luthier. It does not benefit the player in any way.
Regardless of the width of the neck, some curvature in the fingerboard profile, or radius, is always helpful in making the guitar easier to play. I have read about classical guitars with a very slight curvature, 24-inch or 20-inch (610mm or 510mm). Mine has a 15-inch radius, like a Martin steel-string guitar. A greater curvature, say a 10-inch or 7.5-inch radius like on a Strat, would probably be more than a nylon-string player would want.
The late Thomas Humphrey, builder of the Millenium Guitar, championed a slightly radiused fretboard on his traditionally-proportioned instruments with full-width fingerboards. He mentioned that in addition to comfort and playability, it was helpful to increase the curvature under the bass strings to enable a slightly greater string height to correct problems with string buzzing.
Obviously, it’s easier to plane a flat fretboard and hammer in flat frets. With a radiused design, you have to sand or mill the fretboard to a specific tolerance, and you need to individually bend each piece of fretwire to match that radius before it is hammered in to the fingerboard, in order to get a good fit. Finishing the frets by leveling and polishing is a bit more complicated also. Then you need a radiused profile on the nut and the bridge saddle, and this probably complicates intonation compensation. All this takes time and money, but boy is it worth it to the player.
Cutaways are good. You can play the high notes more easily.
The idea of the cutaway first came from archtop steel-string guitars in the 1930s, and was incorporated in to the design of most solid-body electric guitars. Additionally, many models of steel-string acoustic guitar are available with or without a cutaway.
I won’t offer any verifiable data here, because the cutaway issue has been discussed far and wide for many years. Let’s just say that traditional classical guitarists have not approved of the cutaway because it simply makes the guitar look unlike a traditional classical guitar. The cutaway remains an unpopular option for serious, acoustic classical guitar players. But the cutaway is gaining acceptance. It’s been demonstrated that the presence of a cutaway does not necessarily alter the sound, volume or projection of a guitar.
One of my tenets in this blog is that classical guitars should break from tradition in terms of size and shape if there are innovative new ideas that prove beneficial. So I would like to ask traditional classical players to be more open to new shapes and dimensions for their guitars. Why must all guitars look, externally, just like the ones they built in Europe in the 19th century? If somebody builds a design that’s easier to play yet sounds just as good or better, it shouldn’t be rejected just because it does not look orthodox and conformist.
If you want to do some outside reading, I would refer you to the Web site of the famed and innovative builder , who discusses different designs with regard to scale length. Unfortunately there’s not a lot of information on the Web about Thomas Humphrey’s design principles, since his passing and the abandonment of his Web site and domain. I’m sure you can find many other links. The biggest area of innovation is in the construction of the tops of the guitars and how they are braced, and that’s way outside the scope of my blog.