Fretboard floating above soundboard
 

I've seen a few guitars (mostly archtops) where the fretboard does not touch the soundboard and instead floats above it. That's a fairly large area of the soundboard, so presumably leaving it free to vibrate would be beneficial (considering how some people are up in arms about the tone-destroying impact of a little arm bevel). Can some of the builders shed some light about why the floating fretboard isn't more common in flat tops? Is it tradition, cost, difficulty?

I suspect that Mike Baranik, Kent Chasson or Howard Klepper, (among others) all of whom offer guitars with this feature can chime in on this one. The guitar that I just took delivery from Kent incorporates an adjustable, elevated fingerboard.

http://i1238.photobucket.com/albums/...ps26af7b2a.jpg

For me it's the weight and balance. Guitar tries to tip forward when playing seated.

No balance issues on archtops because they need the neck tilted back a lot further (the top raises up higher, and the bridge is taller).

I can only guess but I do know that it can be hard to buck tradition.

Once you get it engineered, it is not significantly more costly. It's a bit more difficult and more time consuming but if it's part of an adjustable neck, that extra time is partly offset by time savings in the neck set and final setup. The biggest cost is in figuring out the engineering. There are some potential issues that aren't immediately obvious. I've heard from a few builders who gave up after their first attempt went bad.

Like the dovetail vs bolt-on argument, there are some who believe that a very solid neck joint with attached fingerboard is tonally important. I believe there can be tonal consequences of a floating fingerboard but they are generally positive.

If used with an adjustable neck, there are many benefits. One that is less obvious is that the saddle height and the action are independent of each other. That means that I can adjust the saddle height for the tone I want and keep it that way while the action is adjusted with the neck.

Another is that the player can easily make seasonal action adjustments and do so without removing the strings or messing with the saddle.

Many players find that fretting over the body is easier with the fingerboard elevated.

Archtops need it (although the less expensive Gibsons had the board right on the top) because of the height of the arch and the height of the bridge. For flattops, the reasons you don't see it much are tradition and a little extra construction cost.

I don't think there is much of a tonal advantage in not gluing the fretboard extension. I glue as far as the end of the neck block in any case, since that is already dead territory. But I think there is some change in tonal envelope from having the strings pull more upward on the top. There is a bit less torque on the bridge and a bit less of the frequency doubling caused by the string tension changing twice per cycle. But not a major change, and easily swamped by other design elements.

The frets over the body are easier to reach, especially for a classically trained player.

Until reading Dekutree's post, I never heard anyone say that their guitar tips forward with a raised fretboard extension. But the neck ends up set at a slightly negative angle to the top (to avoid an overly tall bridge). It is not, however, necessary to have the neck set negatively to the sides. I set the neck square to the sides, and taper the body thickness on the top rather than the usual taper, which is on the back. Builders will get that; sorry I lack digital drawing skills.

The mechanics of it take a little figuring out, but then construction is not more difficult--it just has another couple of steps-- and even has some advantages when fretting and binding the board.

I do this on my instruments, mostly since it permits the vertically adjustable neck that is one of the features I incorporate. Obviously, one can't slide the neck around if the fingerboard is attached to the face!
http://i1260.photobucket.com/albums/...psa3934cb0.jpg

My fingerboards are supported underneath with a 5mm laminated carbon fiber plate, which extends into the neck from the heel end. This makes the extension extremely stiff, and couples those upper frets to the neck so they don't sound thin compared to the rest.

I agree with Howard et. al that there is minimal (if any) tonal effect - most guitars have a heavy brace up there, which IMO acts as a pretty effective boundary that isolates the neck block area from being particularly active.

However, I also agree with Kent that it is a VERY useful feature to be able to adjust bridge height (and thus, soundboard load) and then dial in the neck to compensate. This is a vital part of my setup process, on a per-guitar basis, and I really feel like it lets me hit the sweet spot for each instrument by making small adjustments to the overall string pressure.

Cheers,
Martin

Thanks so much for the detailed answers!

This is what I've come to believe from reading I've done. The large transverse(?) brace that stretches across the entire top, just above the sound hole on a flattop guitar, creates a boundary which effectively stops the area above it from vibrating. So a fingerboard extension glued directly to the guitar's top in that area should not be a negative as far as tonal characteristics are concerned.

But some builders don't use a transverse brace in their upper bout bracing design. There are alternative methods of handling the string load that may allow for enhanced upper bout movement when the fingerboard is elevated.

http://i1238.photobucket.com/albums/...ps5a045404.jpg

McPherson builds this way, along with the offset sound hole, and claims it allows much more of the top to vibrate. Those guitars sound very nice, though I can't say it is just those particular features.

http://img.photobucket.com/albums/v2...e2you/kr03.jpg

You can barely see that the fingerboard is elevated on my KR 7 string. He uses some graphite rods under the extension. My next one won't have as many frets since it'll be a non-cutaway.