- Scale length, which is the approximate length from the nut to the bridge. Fenders are typically 25.5", Gibsons are typically 24.75".
- Headstock format/angle. Fenders generally have a straight headstock where the face of the headstock is simply milled down from the level of the fingerboard to provide the break angle for the strings, while Gibson and most others attach the separate headstock at an angle
- Nut width, which is the width of the neck at the nut. Use of a Floyd Rose locking nut, Fender LSR nut, or the various species of compensated nuts will tend to dictate nut width, but a traditional cut nut has no limits.
- Bridge width, which is the width of the string spread at the bridge.
- Fingerboard radius, which is the curvature of the fingerboard. Fingerboard radius is implicated in the choice of bridge and nut. If I choose a flat radius (easier to implement and fret by far), I couldn't use most pre-constructed nuts, all of which have a finite and definite radius - there would be string height mismatch. For instance, Fender LSR nuts have a radius of about 9.5", which works with a 10" radius. Floyd Rose locking nuts come in limited radii; the originals were 10". Gibson-style Tune-o-matic bridges generally have a 12" radius.
The taper of the neck, as seen from the top, will be dictated by the string lines connecting the nut to the bridge, leaving something left over at the edges for bending. The scale length will dictate how far that bridge is placed from the nut, so it figures prominently in the geometry. The choice of radius may determine which bridge and nut I use, thus indirectly locking in the neck taper.
Scale Length/Fretboard Radius
I'm going with 25.5" because I want a compound (conical) radius fretboard: http://www.stewmac.com/shop/Bodies,_necks,_wood/Electric_guitar:_Fingerboards/Fender_Scale_Compound_Radius_Fingerboard.html
Headstock Angle
I thought I might angle the headstock back. Fenders are a little weird to me with their use of string trees to increase the break angle of the higher strings. There are a couple of ways to implement the angled headstock pattern:
- One piece of wood - potentially weaker because the grain breaks going around the corner
- Scarf joint - as strong as the joint and the glue used to make it
- Finger joint - I thought I'd make one of these, just to be different
However, there are two issues with either the scarf joint or the finger joint, neither of them trivial in my case: cutting this stuff (as always) accurately, at a very low angle, and the wood consumption issue. As you can see from the following picture, a 10 degree angle will use up at least 6" of wood. I can just about spare that, but not a bit more. I can't begin to comprehend whether cutting a 10 degree angle the wide way across a 1" board is doable with a band saw, or if I would have to use a hacksaw. Either way, big adventure.
Most headstock angles range from 10-15 degrees or so. If I want to use an LSR nut, which is intended for use with non-angled Fender headstocks, any kind of angle might cause clearance problems with the back edge of the nut, in particular the rubber dampers out back (I could surely just trim those?). Floyd nuts don't care - there's a big ugly string tree behind it, pulling the the strings way down low to position them over the clamping surface.
On the other hand, my G&L S-500 Tribute has a non-angled headstock with staggered-height Sperzels and seems to work fine.
Nut Width/Bridge Width
Due to my choice of fingerboard, the nut must match a 10" radius and the bridge must be able to accommodate a 16" radius. The former rules out very little, but the latter rules out Tune-o-matics among other bridges. My mind swings wildly between a full-on Floyd trem setup and a simple, traditional Graph-Tech nut with a top-loading fixed bridge. In between I've conjectured the following:
- LSR with Sperzels, generic height-adjustable top-loading bridge
- Floyd-style locking nut with Floyd bridge stripped down and bolted to the guitar face in fixed-bridge configuration
- This: http://guitar-bridge.com/hp135009/Guitar-Bridge-Hannes.htm
- All the rest
I don't like string-through-body bridges because I imagine that the sharp 90 degree turn made by the string at the bridge causes tension to get stored on one side or the other, which when released results in tuning problems. I don't know this, mind you, I just made it up as a theory. There's a guy I know who mostly plays Floyd-equipped guitars and never, ever uses the bar, and says its because they never, ever go out of tune. My theory on that one is that the locking nut is responsible for most of that, and the spring tension compensates for changes in the guitar geometry due to expansion, contraction and moisture retention. But trems are not in my opinion great for sustain, and when you bend a string generally all the other strings ring flat. I could try a Kahler, but I'm scared of all the machinery - and they're just as expensive as a good Floyd.
Conclusion
So you see, I'm trapped in a nest of quandaries. The text above is only a bare beginning of a description of what goes through my head when I think about this. I don't have to hurry, but at some point I do have to choose.