I'd like advice on cantilevered fretboards!

[Dave Bagwill]

Does anyone here have a good explanation, drawings, photos etc of making the elevated or cantilevered(I know they are different) fretboard as in the picture? Some details you've picked up by doing one?
I'm trying to come up with a plan on how to approach it. There is some information here : https://theartoflutherie.com/the-elevat ... ar-design/
A better explanation here: https://www.bamburgguitars.com/single-p ... e-Big-Deal

[Dave Bagwill]

Also this guy gives an explanation. Here's a pic of his bracing. Interesting.
Ya know, the more I read, it seems clear that if one wanted to keep the usual neck angle (1 degree or so) but still get the benefits of no utb, a smaller headblock, and the elevation of the fretboard, one would only have to build the instrument a 1/2" or so less high at the headblock. Everything else would stay the same.
For a player that actually uses the frets over the body, this may not be a perfect solution, but that could be gotten around I think.

[John Parchem]

Interesting, there is a bit more of the top that would be active. The link you sent looked interesting. It took me a bit to visualize controlling the angle with respect to the top until it dawned on me that with the fret board detached from the top using the top of the saddle as a pivot point the neck (including string with the same action) can rotate changing the angle that the strings hit the saddle. It offers one extra degree of freedom in the design.

I have never built an instrument with an elevated neck but I have been thinking of it for a classical guitar. In that case I was planning on keeping a normal angle of the strings on the saddle. To get the elevation I was going to start a tapper of the body just past the waist Basically instead of elevating the fret board I was planning on dropping the top.

[Hans Mattes]

The last four guitars that I've built have featured an "elevated fretboard." As in Dave B.'s note, my motivation was to free the upper bout. But the elevated fretboard is only a part of that process; to be "free," the soundboard's upper bout can't be encumbered with the traditionally massive upper transverse brace. Yet the need to prevent the headblock from rotating under string tension remains.

So I've tried various approaches:
1) a "floating UTB" that crosses the upper bout north of the soundhole but is spaced away from (below) the soundboard and its light bracing. This brace (I've used a carbon fiber bar) is held by mahogany blocks fitted to the inside of the curves of the upper bout and is then braced firmly to the headblock;
2) two wooden braces (about 2" wide by ¼" thick with several 1" holes along their length) running from the headblock to the tailblock but not touching the top (and its braces) or the back (and its braces). These longitudinal braces need to be stiffened by linking them together south of the soundhole with a modest brace to prevent their bending and resonating;
3) braces from either side of the headblock to mahogany blocks fitted to the waist, supplemented by braces from those blocks to the tailblock.
For a variety of reasons, I'm coming to favor style 3, though all seem to work.

To implement the elevated fretboard, I use a bolt-on neck with the heel of the neck riding directly on the headblock and no mortise/tenon other than the thickness of the sides. I build the heel with parallel sides (about 2" wide) and slot the bolt hole in the headblock so that the neck can be adjusted up/down by around ⅛". The recess of the neck heel by the thickness of the sides lets me trim the angle of the neck with thin shims. This combination of movements allows adjusting the height of the strings above the soundboard separately from adjusting the height of string action above the fretboard. And, should a neck adjustment/reset be necessary, it's really a simple operation.

So, how does it sound? I like it (but that' probably not surprising). Objectively, I can say that the upper bout does vibrate -- I can feel it with my fingertips when I pluck a string. I think that the sound with the freed upper bout is a bit richer, adding resonant areas and more harmonics to the soundboard. These guitars certainly have significant sustain.

[Dave Bagwill]

Thanks Hans, good info.

Do you keep the neck angle at the same 1º or so as you would normally? Do you use any reinforcement under the fb extension?
The way I envision the process is simply to slope the upper bout enough to give the fb clearance. That does not increase the string tension over the saddle as a true cantilevered system would, but does have the benefits you pointed out.
However, if I do slope the upper bout, what do I do about the truss rod?

That slot in the side material that your heel fits into - gads, that has to be just perfect, right? No room for error or the cosmetics woule be terrible. But I like the idea.

[Hans Mattes]

Regarding neck angle with the elevated fretboard, I cut the neck heel at 90 degrees to the fretboard surface and contour the top with a 30' radius dish. The adjustable neck allows that to work.

Regarding the fb extension -- I've use mahogany neck material under the entire fingerboard, though under the neck extension it's fairly thin (around ¼" near the heel edge and ⅛" at the end of the fretboard). I've tried three approaches to truss rods/neck reinforcement: First I used a conventional truss rod, with access from the south end of the fretboard, but wasn't at all happy with the result. (Headstock access to a truss rod would be better, but I don't like the look of an access plate.) Next I used a ¼" x ⅜" carbon fiber rod embedded in the neck shaft all the way through the neck extension and that worked out ok, though it limited my ability to contour the extension. Now I use two ⅛" x ⅜" carbon fiber rods epoxied into the neck shaft from the nut to the heel, but not extending south of the heel. The fb extension gets no extra reinforcement other than the neck material. I dress the frets flat and find that 150-170 lbs. of string tension gives a few thousands of relief. The adjustability of the neck makes that quite enough to allow low action without buzzing.

Before the first build of the series, I was concerned, as you point out, about the "perfection" needed when slotting the side material for the neck. It's not that hard -- the critical issue is to get the sides of the neck heel truly straight and parallel. I build the neck first and then use the heel as a template when gluing the sides to the headblock. (Cellophane packing tape on the heel temporarily provides a glue-proof surface as well as a small clearance.) I've been surprised at how well it all works. Easy, peasy.

As far as the angle of the strings over the saddle, I don't think there's any increase in tension, but the angle is a bit different with an elevated fretboard. Some folks have claimed that contributes to a "sweeter" sound. I really couldn't say, as there are a number of other significant changes from the traditional build; but these guitars do sound sweet, harmonic, rich, etc. (at least I think so).

[Dave Bagwill]

Ah! No truss rod, then, but the CF rods will allow the strings to pull a bit of relief into the neck, plus you can adjust the neck up and down as needed. Neat solution.

Do you elevate the fb in effect by sloping the top to create the space between top and fb?