I brought this same subject up about three years ago, but searching the index I haven't been able to find it.
Okay, here's the history of fanned frets. During the middle ages a luthier came up with the idea of using longer strings on the bass strings than the treble. The main reason was that strings of thicker gauges were not available, so the only way to get lower notes while keeping the tension playable was to use longer strings. To that end many citterns of various shapes and sizes were built with fanned frets. No lutes were ever built with fanned frets because a lute's frets are tied and you couldn't tie fanned frets and keep them in place. I've been building mediaeval instruments for decades, and the photo that Basil included was of a Bell Cittern that I built about ten years ago.
(This photo was taken before it was strung up, so you can't see the floating bridge.)
During the 60s there was a lot of experimentation going on, and a lot of fanned-fretted flat-backed mandolines were made by a luthier in Berkeley, CA. This led to Ralph Novak specializing in building fanned-fretted solid electric guitars under the name Novax Fanned Frets, and he has been doing a good business in this for many years. Unfortunately he patented the idea and I've had a longrunning dispute with him about patenting an idea which has been around for centuries, but that's another story.
The modern idea of fanned frets on an electric guitar is for comfort of playing. There are jazz guitarists out there who are very enthusiastic about it. I've seen a fanned-fretted classical guitar, but it failed to garnish any support from the classical world. Basically, it compensates for the angle of the arm to the fingerboard, which changes as you move up and down the frets.
The application of fanned frets to a steel guitar would be backwards to that of a regular guitar, because of the playing position. Think of your arm as a windshield wiper. As you slide up the strings you have to alter the angle of the steel in your hands to keep it parallel to the fingerboard despite the fact that the angle of your arm is changing. This is the well-known parallax problem that all steel guitarists are aware of. A fanned fingerboard completely does away with the parallax problem. Unfortunately, experienced players have learned to automatically overcome the parallax problem, and designing the fingerboard as a fan would throw them right out.
Now to the practicalities of building one. The first thing you have to decide is where the straight fret will come. For instance, you could have a straight nut and everything fanned out from there, or you could have a fanned bridge and everything fanned out from the other end. Most luthiers who build fanned fingerboards place the straight fret at about the 12th, and fan out in both directions from there. The next problem to decide is the radius of the arc. Logic says that it should be about the distance from the middle of the left hand to the elbow, but in practice that usually ends up too short. (In case I've lost you, look at the cittern in the photograph: there is a spot where all the frets would converge if drawn out, and that is the centre of the fan.)
Looking at the photos of the instrument that Randy is trying to replicate and improve on, my suggestion is that the radius of the arc is too small, and the frets should be fanned less.
....well that's my ten cents worth
Glance away from that fretboard for a little too long and you'll be playing slants whether you want to or not!
