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Note, I'm talking about an elevated fingerboard, as in over the body not just raised. (so that there's space between the tongue and the upper bout).

1- Does doing this actually free up the top bout to move, or does the structure braces that exist there make it negligible ?

2- Have you ever made one? If so what was your experience

3- Perhaps there are more, but to me it seems there are 2 ways to accomplish it and still have a good break angle at the saddle.
A : bring the headstock forward at a greater angle
B : create a steeper radius from the waist forward

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This has been something I've been rolling around in my head for years, but have yet to actually try it. Do I NEED to try it? No. Do I WANT to try it? Maybe ... haha

Thank you for your input:
B

I've made raised fingerboards on classical guitars for upper fret access (it does help) and on archtops, but I don't believe that's what your talking about. I've done it through the neck angle.
I don't believe you would gain much if anything considering the neck block, upper transverse brace and the fact that there's a 4" hole right there too, but that's just my opinion.

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Jim Watts
http://jameswattsguitars.com

Draw it out first…

I am currently building an archtop with a floating fretboard extension. I'm following Bob Benedetto's instructions for how to make the little support piece. I cut and fit the dovetail first, then added the support, then glued the f/b on. I put two carbon fiber beams in the neck mostly to support that extension.

The extension just touches the top at the very front of the guitar and is barely above the top as it extends towards the bridge. The geometry was laid out so it would just clear the top







Its going to create a few problems with finishing - in order to finish under the f/b extension I'm going to have to finish neck off the guitar. I think archtops are often finished with neck installed.

so to keep your string height right and the break angle decent at the saddle did you dip the upper bout? Or did you pull the headstock forward a little ?

Well, the geometry of an archtop is way different from the geometry of a flat top but the goal is still the same. I want the fret plane to just touch the top of the bridge with the bridge/saddle set as low as it will go. Overstand, neck angle, top arching and bridge height all factor into that. The break angle on an archtop is different too with the floating bridge and tailpiece.

However, what I did is exactly what Meddlingfool said to do, I laid it out on a piece of paper before I started.

I use floating fingerboards on archtops too. It's a different animal; there is usually no upper transverse brace on an arch top, unless it has a round or oval hole, and even then it doesn't go all the way from one side to the other.

It's not hard to look at the low frequency vibrations of a guitar with a signal generator and Chladni patterns. Even on arch tops the loudspeaker like 'main top' resonant mode doesn't extend all the way to the edges of the upper bout. It's usually sort of egg shaped, with little, if any, motion out in the wings. On 'X' braced flat tops it will extend a bit up past the waist, but not usually very far, and on Classicals it generally stops near the waist, although it often gets up higher than the waist bar. The 'main top' mode, working with the air in the box, produces most of the actual power output of the guitar, possibly all the way up to 1000 Hz, simply because it's so much more effective than anything else. It's good to maximize it, but not easy to push it very far up without compromising the structure.

indeed.

I built an L00 style guitar with a floating fingerboard/adjustable neck. The tenon will slide up and down in the mortise to allow action adjustment--the holes for the mounting bolts are actually slots. I used an archtop style heel with straight sides so that moving the neck up and down won't mess up any finish that is ever seen. I'll build more like it--I do think it frees up the upper bout to some degree, but I like the idea that fingerboard cracks in the top ain't gonna happen as well as the adjustability. The arrangement required a slight forward neck cant. As others have mentioned, I drew it out full size first to figure out neck angle and such. The top is domed in its entirety--upper bout isn't flattened at all.

I basically did it the same way I do archtops.

The angled end of the extension in the third picture was cut off--it was made from a piece of scrap from scarfing the peghead, and had that angle on it....

I've attached some under-construction pictures.

Dave

i think the info here may be a good starting point.
https://theartoflutherie.com/the-elevated-fingerboard-guitar-design/

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I agree. Good starting point for sure.

Dave

I have always been fascinated by Charles Fox's Ergo Acoustic Guitar, quite an extreme example maybe, with may other sort of "novel elements."

https://www.premierguitar.com/builder-profile-charles-fox

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Please forgive me for piping up about ukuleles but that is where my experience lies and it might have application to guitars. I've been building with a cantilevered fretboard for close to a dozen years and my experience is that this feature doesn't do much, if anything, to improve tone. The transverse braces that are adjacent to the sound hole make sure of this but it is possible to build in a way that allows the entire top to vibrate and produce sound.

I've recently found that by eliminating the transverse braces, tone can be much improved, including volume and sustain. Instead of repeating myself, I'll refer to my blog posts beginning on July 9, 2021, the first of which describes a construction technique that eliminates the transverse braces. The later posts are various sound samples.

http://onoukes.com/blog

Interesting Blog, and nice ukes!

Dave

I have done 3 and find the top area that can vibrate is moves forward over 2" towards the neck block, my 1st pictured below had a smaller UTB brace and was very good. Since I like to experiment I removed more wood from the UTB and it moved active area farther forward. On the 2nd the UTB is even smaller in cross section with great results. My 3rd is a nylon crossover but is still in the lacquer curing stage so no info on it yet.



Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

A very interesting guitar - Double top, bolt on bridge, and the wedge body is done by angling the top, not the back.

I think part of the allure of the elevated fretboard (on flattop instruments) is that you are getting "straight pull" so that the the strings are parallel to the face.

Very nice! That's just about what I had in mind for opening up the upper bout to vibrate. With the soundhole in the usual position, the upper bout is largely isolated from the bridge, so you at least need to offset the soundhole like McPherson (although they don't actually do it for that purpose since there's still heavy bracing up there and a cutaway which eliminates a lot of the would-be active area). But moving it partially or entirely off the soundboard is even better. I really like that redwood top with the soundhole split between the soundboard and side. Some for the audience and some for the player, without sacrificing much active area to it.

And the buttress braces are a great way to free up the soundboard to focus entirely on tone instead of balancing tone and structure. I'd recommend putting a back brace across the waist and two more angling up from there to the headblock. Together with the headblock and buttresses they form a tetrahedron, which is one of the most naturally rigid shapes you can get.

Another thing to consider when scaling up to guitar size is that the longitudinal soundboard braces should either be fairly fat or more angled relative to the soundboard grain. Otherwise they will imprint through, and won't spread the stress over as much of the soundboard wood. One interesting approach would be to change the angle of the soundboard grain rather than the angle of the braces Since the braces angle inward from head to tail, have the soundboard grain angle outward from head to tail.

I haven't considered this seriously in any of our designs... but, I have done some research into the design theory of McPherson's guitars. From what I can summarize, the theory of the elevated fretboard in their guitars is all about letting the upper bought participate in the resonance. Consider a violin, and how it allows the entire top plate to vibrate. This means you have to deal with the realities of the traditional transverse brace (and it's effect of killing almost any upper bought vibration) and the traditional sound hole's effect of scooping out most of the upper-mid vibrations.

I think the reality is that once you commit to detaching the fretboard from the upper bought, you need to decide why. If it's aesthetic, then get on it and have a good time. If you are expecting significant tonal improvements, then I really think you have to look at your entire top bracing strategy and sound hole placement in order to get the benefits of said efforts. Raising the fretboard and reducing the upper bought to accommodate is going to look different and reduce the overall volume of your body's airspace for resonance. I don't see either of these as a great thing. If you keep the body the same size and shoot the higher neck at a steeper angle to the bridge you probably aren't gaining anything other than a canted fretboard angle, that some people might like and others not so much.

My approach to building is to take time-proven designs and execute them in ways that are carefully considered, so that my guitars will sound and feel better then those hanging at the wall of the local guitar shop. I don't experiment for the sake of exploration, because my purpose in building isn't to see what I can invent. The guitars I build are directed at a market that isn't looking for something new and different. They are looking for something that's familiar, comfortable and emotionally inspiring so they can make their best music.

I think it would be fun to try this thing, but at this point it's off my radar.

On the one flattop I've done, I kept the thickness of the body in the upper bout the same as it would have been with an un-cantilevered neck. I just tapered the top instead of the back. It does look different, but the airspace is unchanged. The sides are perpendicular to the back instead of the top is all. I built this guitar with tentelones, so the workboard had to accommodate the taper of the top though. No biggie, but it was an extra effort.

I agree that there needs to be a good reason to build like this. For me, it was the adjustable neck (and being able to keep a flat fingerboard without a top becoming an issue--an advantage archtops have had) and reducing the likelihood of fingerboard/top cracks.

Dave

TerrenceMitchell wrote:
"Consider a violin, and how it allows the entire top plate to vibrate."

It's almost always a mistake to bring the violin into a discussion of guitar acoustics. It's such a different system that there's really very little in common except strings, wood, and air. Violin strings drive the top by moving horizontally across the body; the bow drives them that way, and won't allow for useful vertical motion. The bridge top rocks sideways, and it pivots around the treble foot, which is more or less fixed in place by the sound post. This causes the bass foot to move up and down and push the bass side of the top. The bass bar distributes that motion along the length of the top to pump air in and out of the holes. On the guitar, with no sound post, the vertical vibration of the plucked string pulls the top directly, causing it to work like a loudspeaker, at least at low frequencies.

Again, my experience with arch top guitars suggests that the vibrating area of the 'main top' mode does extend further up toward the neck without the UTB there, but the actual increase in vibrating area is rather smaller than you might think. In order to get that you have to arch the top and leave it thicker, to take the load, which makes it harder to move. It's a balance between increasing the vibrating area and avoiding reducing the amplitude too much in proportion. Most archtops simply build heavy and add a pickup for volume: they cheat...

I've built a couple of dozen guitars, both with and without an elevated fretboard. Unless the guitar is also constructed without a UTB (and, heaven forbid, a popsicle brace) the upper bout is still quite constrained. To "free" the upper bout requires light bracing over the entire soundboard, so I've been using "flying" internal braces between the headblock and the tailblock (usually with the bracing also blocked to the inside of the waist). That provides a solid construction without requiring the soundboard to act as a structural member. The upper bout then becomes quite active. But that doesn't translate to much greater acoustic output, as the increased area is only around 40% to 50% of the lower bout and the ear can barely hear a 2dB increase in volume (and that's with a step input of a constant tone). What the active upper bout does provide is more resonances available to sustain the harmonics produced by the strings. That's reflected by a "richer" sound and more sustain. Whether you want a richer sound and more sustain is an entirely separate issue.

If there's anything I'm an expert on... it's making mistakes. Especially when my efforts are in the pool of "almost always a mistake". Disclaimer - I'm no luthier... I'm just a woodworker with 30 years of experience, and a musician with more than that who makes guitars for a purpose.

Best advice this old guy can give... Don't take my advice until you've played one of my guitars. And don't reject it until you've played one of my guitars.

Build on everyone!

That's a nice description. Thanks!

Dave

Terrence:
I'm not questioning your results, just the analogy. With something as complicated as the guitar it's easy to end up doing the right thing for the wrong reasons. There's not even anything wrong with that, until you try to push it too far; things stop working the way you expect, and you don't know why.

Hans Mattes wrote:
"The upper bout then becomes quite active. But that doesn't translate to much greater acoustic output, as the increased area is only around 40% to 50% of the lower bout and the ear can barely hear a 2dB increase in volume (and that's with a step input of a constant tone)."

Fred Dickens once said he'd cut off his left hand for 1 more dB. I don't quite agree, but he had a point (as he usually did). The added output may not sound 'louder' up close, but it does tend to 'carry' better.

When you make the vibrating area larger you also have to maintain the stiffness. With a larger span that means either making the plate thicker, or beefing up the bracing. Richardson says that the power output is proportional the ratio of vibrating area over mass. With a given structure and materials increasing the area requires adding mass out of proportion to maintain stiffness, so the power output actually goes down. It's generally easier to make a powerful small guitar than a powerful big one, but then there's the issue of treble/bass balance. There seems to be an optimum size for any given guitar top structure.

Looking through Evans and Evans book I noticed that the early gut-strung ladder braced guitars all tended to be about the same size. When fan bracing came in, around 1775, the lower bouts started to get bigger, finally settling down to a more or less standard size of 14" wide or so, around 1850. X-bracing is a bit more efficient structurally, and gives a different timbre that really came into it's own with steel strings. Those tend to top out at around the size of Gibson 'Jumbos' and Martin 'Dreads'; 16"-17" wide. With carved arch tops the limit seems to be more ergonomic; you can make a 19" wide body that is structurally and acoustically fine, but it's hard to play it like a guitar. I've made a few arch top classicals at 16" wide, and it's a trick to get the timbre right, but they do produce more sound. It would not surprise me if something like the Gibson 'Mark' bracing, or it's close cousin, the Taylor 'V', could be made with a longer body without messing up the A/m ratio, but that would require some experiment. In the past these advances all seem to take about 75 years to be fully optimized, and then there's the question of who wants it.