Cantilever neck

[creekrat]

I’m looking for someone that’s built a cantilever necked guitar before. I have a few questions about the design aspects of it. Like if you incorporate say a 1/2” drop from the waist to the top of the guitar can you then just increase the neck thickness above the top by that same 1/2” above the plane of the top and shape accordingly to have the fretboard extension “float” over the top?

[coldfingers]

I'm not sure exactly what you have in mind, but I've built several archtop guitars and ukuleles with cantilevered next extensions. As with any guitar, the neck angle and fretboard height above the top must be designed to "aim" the strings at the target bridge saddle height while maintaining the desired playing action. It's a good idea to make an accurate scaled drawing of these geometric relationships if you're designing your own instrument.

In an archtop guitar, there is usually an extension of the neck as well as the fretboard. The first 1-1.5" inches (over the neck block) is usually flush with the top, and the rest floats. To do this, you either have to carve your neck joint (some kind of tenon, presumably) by hand under the extension of a one-piece neck, or glue on a separate extension piece after the joint is routed.

[JonWint]

I built a Martin Stauffer style guitar with a dead-flat top. As coldfingers said you have to "aim" the neck to hit the bridge location that is required. That's why the fretboard extension thickness is tapered

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[creekrat]

Thanks for the reassurance and insight. Pretty much what I had imagined. I would definitely start with drawings as close to scale as possible and can always dial it in when cutting the tenon. I would probably do a bolt on neck where I would get a good tight fit and then place my threaded material in the tenon

[gtrboy77]

How would I incorporate enough of a drop in the top for a cantilevered neck if I was already using a 28’ radius dish for the top? It almost sounds like I would need to make some sort of compound radius dish for that.

Originally Posted by coldfingers

I'm not sure exactly what you have in mind, but I've built several archtop guitars and ukuleles with cantilevered next extensions. As with any guitar, the neck angle and fretboard height above the top must be designed to "aim" the strings at the target bridge saddle height while maintaining the desired playing action. It's a good idea to make an accurate scaled drawing of these geometric relationships if you're designing your own instrument.

In an archtop guitar, there is usually an extension of the neck as well as the fretboard. The first 1-1.5" inches (over the neck block) is usually flush with the top, and the rest floats. To do this, you either have to carve your neck joint (some kind of tenon, presumably) by hand under the extension of a one-piece neck, or glue on a separate extension piece after the joint is routed.

[MC5C]

I build archtops with cantilevered necks - the simplicity of the cantilever is often overlooked, and I think it can work well with any style of guitar. A friend builds classical guitars with cantilevered necks. There is basically little stress on the fretboard extension but it needs to be strong enough to withstand fretting pressure. Mine are usually 1/4" of fretboard on top of 3/8" of neck. You need to draw a full scale side view of your instrument to determine height off the top at the body edge, and neck angle. An archtop usually has 3.5 - 4.5 degrees of pitch back, while a classical guitar neck will probably have 2 or 3 degrees of pitch forward so the string height at the bridge is correct. The cantilever frees the body and top from having to support the fretboard extension and you might be able to brace the upper bout differently, particularly if you incorporated buttress extensions from the neck block the way Rick Turner has done (he uses a cantilevered neck with a Howe-Orme joint, yet another innovation from the 19th century).

[gtrboy77]

Thank you for the advice. Yes, I plan on sitting down at the drafting board and drawing it out full scale to figure out the angles and dimensions. I wasn’t familiar with Rick Turner’s neck joint, so I googled it. The flying buttresses are an interesting way of freeing up the top from the pressure of the strings. Ironically, I just read an article in a Guitarmaker magazine this week that talks about this thing called the JLD Bridge Doctor, which sort of does the same thing. I guess Stew Mac sells it. I almost thought about getting rid of the big transverse brace between the sound hole and neck and using this system.

Originally Posted by MC5C

I build archtops with cantilevered necks - the simplicity of the cantilever is often overlooked, and I think it can work well with any style of guitar. A friend builds classical guitars with cantilevered necks. There is basically little stress on the fretboard extension but it needs to be strong enough to withstand fretting pressure. Mine are usually 1/4" of fretboard on top of 3/8" of neck. You need to draw a full scale side view of your instrument to determine height off the top at the body edge, and neck angle. An archtop usually has 3.5 - 4.5 degrees of pitch back, while a classical guitar neck will probably have 2 or 3 degrees of pitch forward so the string height at the bridge is correct. The cantilever frees the body and top from having to support the fretboard extension and you might be able to brace the upper bout differently, particularly if you incorporated buttress extensions from the neck block the way Rick Turner has done (he uses a cantilevered neck with a Howe-Orme joint, yet another innovation from the 19th century).

[Howard Klepper]

I've done a lot of my building of flattop guitars with what I prefer to call "elevated fretboard extensions." [I don't think that technically this is a cantilever, since it does not bear any load other than any fretting pressure in excess of what it takes to stop a string at one of the frets beyond where the neck extension support ends. However the entire neck of a guitar can be seen as a cantilever, since it bears a load out at the headstock end that is unsupported by anything other than the neck itself.]

Anyway: Usually on a flattop a line from the top of the tailblock to the top of the headblock is square to the sides, while a line from the bottom of the tailblock to the bottom of the headblock is not, so that the body can taper in depth. And usually on a steel string guitar, the neck is set back at about a 1.25-1.5º angle so that the tops of the frets will point about at the top of the bridge (varying with things such as the doming of the top and how much the top rises under string tension.

For an elevated neck extension, I move the body taper from the back to the top. So the line between the bottoms of the blocks is square to the sides, while the one from the tops of the blocks forms an acute angle at the tailblock, and an oblique one at the headblock. Then I set the neck square to the sides instead of angling it back. You will need to make a drawing to get everything right (or just do the math), but iirc (it has been a few years), I taper the body about 3/4" from tail to neck, and that allows for about a 1/2" elevation of the fretboard over the body at the neck joint with a bridge height of about 3/8".

Here's an example:



Another on a 12-fret multiscale:

[ruby50]

I have a 1933 Gibson L-00 that as smashed and I rebuilt it. For a short time Gibson was putting elevated fretboards on these guitars - maybe like their archtops??

I had to pull the neck, and to do that I had to cut off the fretboard at about the 10th fret. Here are 3 pictures that show it.

First is from the top after the fretboard piece was removed. You cans see that the elevator (?) is a separate piece glued to the top.

Second is from the side, Showing how much of the elevator was glued to the top

And third is showing the wedge I had to install after the neck set.

Sorry, I have never figured out posting pictures on this site.

https://www.flickr.com/photos/ruby16...posted-public/

Hope it helps

Ed

[gtrboy77]

Thanks for the great explanation. This is all starting to make sense to me.

Originally Posted by Howard Klepper

I've done a lot of my building of flattop guitars with what I prefer to call "elevated fretboard extensions." [I don't think that technically this is a cantilever, since it does not bear any load other than any fretting pressure in excess of what it takes to stop a string at one of the frets beyond where the neck extension support ends. However the entire neck of a guitar can be seen as a cantilever, since it bears a load out at the headstock end that is unsupported by anything other than the neck itself.]

Anyway: Usually on a flattop a line from the top of the tailblock to the top of the headblock is square to the sides, while a line from the bottom of the tailblock to the bottom of the headblock is not, so that the body can taper in depth. And usually on a steel string guitar, the neck is set back at about a 1.25-1.5º angle so that the tops of the frets will point about at the top of the bridge (varying with things such as the doming of the top and how much the top rises under string tension.

For an elevated neck extension, I move the body taper from the back to the top. So the line between the bottoms of the blocks is square to the sides, while the one from the tops of the blocks forms an acute angle at the tailblock, and an oblique one at the headblock. Then I set the neck square to the sides instead of angling it back. You will need to make a drawing to get everything right (or just do the math), but iirc (it has been a few years), I taper the body about 3/4" from tail to neck, and that allows for about a 1/2" elevation of the fretboard over the body at the neck joint with a bridge height of about 3/8".

Here's an example:



Another on a 12-fret multiscale: