Question re bolt on necks and glue

[.philip Ingber]

I’m doing a bolt on neck for a 000. It fits nicely and the fretboard fits well against the soundboard. No gaps, nice and snug. So, why glue the fretboard to the soundboard? Doesn’t that defeat the purpose of the bolt-on neck?

My first guitar was a dread, under the tutelage of a luthier. We did a bolt on, but also glued the fretboard. The next that I did was a Selmer-Macaferri which has a wedge under the fingerboard, but no glue.

Advice? Opinions?

Thanks.

Phil

[Stephen Foss]

Phil,

Humidity changes. This could make  your "no gaps, nice and snug" turn into "a gap, good'n'floppy". Imagine playing up in that area of the FB and it slightly depresses when you push down on it. Or, if you have low action and move to a rain forest, string buzz.

Some folks will use a bolt-on FB as well as a bolt-on neck. And other folks (different than "some" folks) design the FB extension with a foot that perfectly fits into a recess on the top (Taylor, I think). There are lots of ways to secure the FB to the top. Glue is the simplest.

I hope this helps,

Steve

[JohnParchem]

I view a glued or bolded fingerboard extension as a structural component tying the neck and  block and if done correctly the transverse brace together. Structurally it provides a wide 6 mm tall brace to help keep the guitar from folding over time. If it is not glued or bolted, the fretboard slides as the string pulls the neck forward. 

[Stephen Foss]

Phil, (and everybody),

I was thinking about your question, and I wondered if small neodymium magnets could be used to "attach" the FB extension? Has anyone tried that? As John pointed out, the FB extension enhances the structure of the instrument at a crucial place; I don't know if magnets would provide this same function well enough.

Merely an errant thought while I butle the cat in/out the door.

Steve

[JohnParchem]

There are a lot of guitars that do not have a  glued down extension. I believe my fear is movement of the neck, first a bit more initially and then over time. Dovetail or bolt on necks on a steel string could definitely use the extra bracing that the fretboard provides. It probably matters less with a spanish heel joint.  The magnets might hold the fretboard down, but would not provide really structurally tie the fret to the top.  I have not done any structural analysis for how much support is needed at this location, I do know that gluing or bolting down the fretboard extension provides a lot more support than not doing it.

[.philip Ingber]

I’m still not seeing the need. If the joint is solid, tight... and the bolts hold it all together, as long as the fretboard is solidly against the soundboard, it shouldn’t be an issue. Of course if there is the slightest gap, it could buzz. 

[Howard Replogle]

Phil,

I wondered the same thing when I switched from dovetailed to bolted necks, until the members of this forum straightened me out.  Re the “purpose” of a bolt on neck: I think the purpose of a bolt on neck is for a good neck attachment, period, and not so a user can remove the neck, like some kind of travel instrument.  It’s true that a bolt on neck is easier (than a dovetail) to remove by a luthier for repairs or adjustments, but it isn’t really intended for incidental removal as might be expected from the term “bolt on” neck.  So I glue my fingerboard extensions down.  A player who removes those bolts and expects the neck to just come off, might be in for an unpleasant surprise!

Howard Replogle

[JohnParchem]

Under string pressure the the headstock is pulled forward. A bow is formed really all the way to the end pins. The bow will be big or small depending on the lateral structural stiffness of the guitar. A stiffer structure will not only resist bowing but also resist creep over time. To use the 6 mm of the fretboard as a brace for structural purposes it has to be glued down. Because brace stiffness increases with cube of the height. 6 mm, even on the heel and block,  matters. Gluing the fretboard  down is a gigantic increase in stiffness between the block and the transverse brace.  

[Stephen Foss]

Very good point, John. Think about how much of a "brace" the 10mm tall bridge is. Extending this thought experiment a bit, those factory-made guitars that have bolt on bridges worked, but didn't produce the same kind of sound as a glued on bridge does. This I have experienced.

See, Phil? Every question can lead to ancillary learning. Keep asking.

Steve

[jwsh...@q.com]

It could still buzz even if the fret board is tight against the top! Scooter

Sent from my T-Mobile 4G LTE device

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[jwsh...@q.com]

If a good neck attachment was the only concern  there would be no need to stray from the classic Spanish heel. Scooter

Sent from my T-Mobile 4G LTE device

------ Original message------

From: Howard Replogle

Date: Fri, Mar 26, 2021 12:49 PM

To: Robert O'Brien Guitar Building Forum;

Cc:

Subject:Re: Question re bolt on necks and glue

Phil,

I wondered the same thing when I switched from dovetailed to bolted necks, until the members of this forum straightened me out.  Re the “purpose” of a bolt on neck: I think the purpose of a bolt on neck is for a good neck attachment, period, and not so a user can remove the neck, like some kind of travel instrument.  It’s true that a bolt on neck is easier (than a dovetail) to remove by a luthier for repairs or adjustments, but it isn’t really intended for incidental removal as might be expected from the term “bolt on” neck.  So I glue my fingerboard extensions down.  A player who removes those bolts and expects the neck to just come off, might be in for an unpleasant surprise!

Howard Replogle

On Thursday, March 25, 2021 at 2:21:33 PM UTC-7 pin...@gmail.com wrote:

I’m doing a bolt on neck for a 000. It fits nicely and the fretboard fits well against the soundboard. No gaps, nice and snug. So, why glue the fretboard to the soundboard? Doesn’t that defeat the purpose of the bolt-on neck?

My first guitar was a dread, under the tutelage of a luthier. We did a bolt on, but also glued the fretboard. The next that I did was a Selmer-Macaferri which has a wedge under the fingerboard, but no glue.

Advice? Opinions?

Thanks.

Phil

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[jwsh...@q.com]

John's last sentence says it all as far as gluing the fret board extension down! Scooter

Sent from my T-Mobile 4G LTE device

------ Original message------

From: JohnParchem

Date: Fri, Mar 26, 2021 1:03 PM

To: Robert O'Brien Guitar Building Forum;

Cc:

Subject:Re: Question re bolt on necks and glue

Under string pressure the the headstock is pulled forward. A bow is formed really all the way to the end pins. The bow will be big or small depending on the lateral structural stiffness of the guitar. A stiffer structure will not only resist bowing but also resist creep over time. To use the 6 mm of the fretboard as a brace for structural purposes it has to be glued down. Because brace stiffness increases with cube of the height. 6 mm, even on the heel and block,  matters. Gluing the fretboard  down is a gigantic increase in stiffness between the block and the transverse brace.  

On Friday, March 26, 2021 at 11:24:21 AM UTC-7 pin...@gmail.com wrote:

I’m still not seeing the need. If the joint is solid, tight... and the bolts hold it all together, as long as the fretboard is solidly against the soundboard, it shouldn’t be an issue. Of course if there is the slightest gap, it could buzz. 

On Friday, March 26, 2021 at 1:12:13 PM UTC-4 JohnParchem wrote:

There are a lot of guitars that do not have a  glued down extension. I believe my fear is movement of the neck, first a bit more initially and then over time. Dovetail or bolt on necks on a steel string could definitely use the extra bracing that the fretboard provides. It probably matters less with a spanish heel joint.  The magnets might hold the fretboard down, but would not provide really structurally tie the fret to the top.  I have not done any structural analysis for how much support is needed at this location, I do know that gluing or bolting down the fretboard extension provides a lot more support than not doing it.

On Friday, March 26, 2021 at 9:08:50 AM UTC-7 Stephen Foss wrote:

Phil, (and everybody),

I was thinking about your question, and I wondered if small neodymium magnets could be used to "attach" the FB extension? Has anyone tried that? As John pointed out, the FB extension enhances the structure of the instrument at a crucial place; I don't know if magnets would provide this same function well enough.

Merely an errant thought while I butle the cat in/out the door.

Steve

On Friday, March 26, 2021 at 7:47:03 AM UTC-6 JohnParchem wrote:

I view a glued or bolded fingerboard extension as a structural component tying the neck and  block and if done correctly the transverse brace together. Structurally it provides a wide 6 mm tall brace to help keep the guitar from folding over time. If it is not glued or bolted, the fretboard slides as the string pulls the neck forward. 

On Thursday, March 25, 2021 at 3:18:40 PM UTC-7 Stephen Foss wrote:

Phil,

Humidity changes. This could make  your "no gaps, nice and snug" turn into "a gap, good'n'floppy". Imagine playing up in that area of the FB and it slightly depresses when you push down on it. Or, if you have low action and move to a rain forest, string buzz.

Some folks will use a bolt-on FB as well as a bolt-on neck. And other folks (different than "some" folks) design the FB extension with a foot that perfectly fits into a recess on the top (Taylor, I think). There are lots of ways to secure the FB to the top. Glue is the simplest.

I hope this helps,

Steve

On Thursday, March 25, 2021 at 3:21:33 PM UTC-6 pin...@gmail.com wrote:

I’m doing a bolt on neck for a 000. It fits nicely and the fretboard fits well against the soundboard. No gaps, nice and snug. So, why glue the fretboard to the soundboard? Doesn’t that defeat the purpose of the bolt-on neck?

My first guitar was a dread, under the tutelage of a luthier. We did a bolt on, but also glued the fretboard. The next that I did was a Selmer-Macaferri which has a wedge under the fingerboard, but no glue.

Advice? Opinions?

Thanks.

Phil

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[Rich]

There are several people that make bolt on necks that are adjustable. For example Lame Horse. No glue used here, Still pretty good guitars. https://img1.wsimg.com/blobby/go/7b1a12d5-7882-45de-a67f-7f0256f18843/downloads/1cdcv4634_618440.pdf?ver=1614794627213

Rich

[JohnParchem]

Rich you are correct there are adjustable, but most of the adjustable necks are still supported with fret board and heel block extensions.   Most of the good designs that I have seen do not apply leverage to the fret board itself. In the example you supplied, you can see in picture 4 that the fretboard is bolted down. I agree that bolts can replace glue. I would not leave the fretboard free. 

[.philip Ingber]

I’m reading the responses with great interest. A few things I agree with, some not so much. Re the pulling of the headstock forward issue... true, forces are on the headstock but... using a Selmer-Macaferri as an example..., free floating fretboard extension, some necks are bolted, others aren’t. They sound fine... wonderful guitars. There are others around that have bolt-on necks which can be adjusted for neck angle “on the gly@, again, fine sounding guitars... and if buzzing under the fretboard was an issue, a piece of felt would do, just as many guitars have it under the tailpiece.

So, I’m still not sure.. but, I’m learning a lot!

Sent from my iPhone

On Mar 26, 2021, at 8:32 PM, JohnParchem <johnp...@hotmail.com> wrote:

Rich you are correct there are adjustable, but most of the adjustable necks are still supported with fret board and heel block extensions.   Most of the good designs that I have seen do not apply leverage to the fret board itself. In the example you supplied, you can see in picture 4 that the fretboard is bolted down. I agree that bolts can replace glue. I would not leave the fretboard free. 

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[JohnParchem]

Well, you asked and I gave you an answer.  After 40 years as an engineer, I tend to look at thing systematically. As I mentioned earlier there are a lot of builders that do not glue the extension down.   Still having the heel block rotate slightly over time is the reason repair people do neck resets.  The fretboard is a free great 6 mm brace to mitigate that very real issue. The good guitars designs all take into account the structural requirements for the string load.  On my Martin style guitars, that only have a popsicle between the block and the transverse brace, I count on the fretboard to be a brace. I do bolt on bolt off necks as well, but those guitars have a heel block extension that goes all the way to the transverse brace. In those guitars the fretboard is just a fretboard. There are guitars with elevated fretboards, but the good designs have support to keep the heel block from rotating.