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Bolt down FB extension
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=50551		 Page 1 of 1
Author:  Bri [ Sun Apr 22, 2018 11:47 am ]
Post subject:  Bolt down FB extension
Would anyone care to share photos of their bolt down arrangement?
I am using a double barrel bolt M&T neck joint and am considering incorporating the bolt down.
Looks like there a few ways of accomplishing this and would like to see what others are using.
Generally I get 1/16-1/32”of fall away, so gluing down isn’t a problem, just exploring options.

Thanks,
B
Author:  Ken Lewis [ Sun Apr 22, 2018 12:17 pm ]
Post subject:  Re: Bolt down FB extension
Here's one, based on the method in Trevor Gore's, "Design And Build" book.
Author:  Terence Kennedy [ Sun Apr 22, 2018 12:39 pm ]
Post subject:  Re: Bolt down FB extension
Here’s mine. I really like Trevor’s with the tenon actually part of the neck but the upper bout has to be co-planar to the neck angle so any extension relief has to be sanded into the fretboard. Kind of like an archtop. Mine is a knockoff of the Bourgeois system.

Image

I think you will find that a double tenon attachment will move more than a glued extension on string up necessitating possibly some upper bout reinforcement and/or a little higher neck angle. Fretboard drop off could be changed as well depending on the type of attachment.
Author:  meddlingfool [ Sun Apr 22, 2018 12:53 pm ]
Post subject:  Re: Bolt down FB extension
The movement was exactly why I abandoned that system and went back to glueing the tongue...
Author:  DennisK [ Sun Apr 22, 2018 2:08 pm ]
Post subject:  Re: Bolt down FB extension
With the Gore style, do the surfaces I marked green here need to be in full contact, or is there an air gap there, with only the blue surfaces in contact?
Attachment:
bolt down.jpg
Author:  Trevor Gore [ Sun Apr 22, 2018 4:24 pm ]
Post subject:  Re: Bolt down FB extension
DennisK wrote:
With the Gore style, do the surfaces I marked green here need to be in full contact, or is there an air gap there, with only the blue surfaces in contact?

You want the green areas in full contact. If you leave an air gap between the underside of the tongue and the pocket then bolt up tight, you risk pulling the fretboard off the neck extension. If you spray finish, and don't sand the pocket, the extra build in the pocket vs. the lesser build on the top because it has had a few sanding sessions gives enough clearance between the top and the underside of the fretboard. A paper shim in the pocket will also do the same job.
Author:  Ken Lewis [ Sun Apr 22, 2018 6:38 pm ]
Post subject:  Re: Bolt down FB extension
"Movement", I haven't seen any, nada, none. I've only done three bolt down extensions like this, the first one is about two
years on now, but I think less movement than conventional with glued extension. The substantial head block and two 1/4"
bolts really lock things in, IMO.
Author:  Terence Kennedy [ Sun Apr 22, 2018 7:00 pm ]
Post subject:  Re: Bolt down FB extension
meddlingfool wrote:
The movement was exactly why I abandoned that system and went back to glueing the tongue...


I copied the Bourgeois joint as described by Sylvan Wells and John Mays a long while back. I was disappointed in the late movement but since it only seemed to occur in the first six months or so and then stabilized permanently I figured it was a little head block rotation. I loved the flexibility of a total bolt on neck.

I shortened the tenon on the fretboard so there was more top glued to the headblock and beefed up the top brace which helped but later found out that Bourgeois leaves a little gap between the end of the fretboard support on the headblock and the top brace and after the top is glued on fits a very tight shim between the two to help with any headblock rotation.

I have been able to do it after routing the mortise as it gives access to the gap and you can wedge in a piece of Mahogany tight and fix it in place with thin CA.

That seems to help a lot with movement in the first year but I would say they still move a little more than a glued extension at initial string up. I am OK with the joint as I am doing it now but it took a while to get there.

Image

Image

I think if I was starting from scratch I would take a hard look at Trevor’s approach. It is beefy and I would guess very stable. Is that the joint you use Ken?
Author:  Ken Lewis [ Sun Apr 22, 2018 8:38 pm ]
Post subject:  Re: Bolt down FB extension
For the fretboard extension, exactly same procedure. Slightly different hardware on the M&T though.
Ken
Author:  Mark Mc [ Sun Apr 22, 2018 9:37 pm ]
Post subject:  Re: Bolt down FB extension
I used this system on a recent build and found that it worked really well. I will use it again. The routing template is very useful.
http://www.luthierscooltools.com/Tools.htm#Bolt-on
Author:  Bri [ Sun Apr 22, 2018 9:59 pm ]
Post subject:  Re: Bolt down FB extension
This gives me a few more things to consider. Ed is considering that the sheer factor of glue joint between the FB and top increases resistance to rotation. Others see some initial movement in the bolt down assembly. For me, I think the top/neck block/ upper brace/ should be considered as a whole, and should be able to be configured in form which resists movement yet allows for simple neck removal. On my last build, I pinned the UTB to a foot on the top of the neck block, thinking that the upper structure of the guitar would become very stable. I have seen various iterations of this and it seemed to make sense. This went to friend so I will be able to monitor it as time passes. Is there a joint which minimizes or negates the need for a neck reset? Are there too many other factors involved or is this wishful thinking? Then, if the joint is totally stable, why design an easily removable neck?
Hmmmm, Maybe I am over thinking this. Back to my single malt....

B
Author:  Mark Mc [ Sun Apr 22, 2018 10:22 pm ]
Post subject:  Re: Bolt down FB extension
There are lots of ways to skin this cat, and no objective evidence that one is superior to another. Therefore, use a method that makes sense to you and is achievable with your skill set and tool box. No guitar is going to be immune to the effects of string tension and other physical forces that lead to the need for a neck adjustment down the track. I think it makes sense to build them in a way that facilitates that inevitable work to be done in the simplest way possible.
Author:  Terence Kennedy [ Sun Apr 22, 2018 10:33 pm ]
Post subject:  Re: Bolt down FB extension
For me a couple of things that I really like about a total bolt-on is that you can bolt everything on and level the fretboard and get the extension drop off correct and can check under simulated string tension and recheck while fretting which I think minimizes surprises when the guitar is strung up for real.

Additionally it is not uncommon to see a guitar back, even with a glued dovetail and extension that moved a little more than you expected and can be fixed by lowering the saddle to a slightly suboptimal height but not really bad enough to justify steaming the neck off and doing a minor reset. You wind up with a saddle that is a little lower than you really wanted.

With a total bolt on you can easily make little minor tweaks in the neck angle and maintain optimal saddle height when necessary.

It's been worth the trouble for me but I must admit that after building probably 75 or more with some variation of the joint I still get surprised from time to time when the guitar does not behave like I expected it to. It is an inexact science.
Author:  DennisK [ Mon Apr 23, 2018 1:16 am ]
Post subject:  Re: Bolt down FB extension
Bri wrote:
Is there a joint which minimizes or negates the need for a neck reset? Are there too many other factors involved or is this wishful thinking? Then, if the joint is totally stable, why design an easily removable neck?

Pretty much all the neck joint types are totally stable. The glue-less ones like we're currently discussing can take time to settle in, especially if the sides and binding are fairly soft material and indent a little under the longitudinal neck force. But stable after that.

The cause for neck resets is gradual deformation of the soundbox. But deformation of the upper bout makes a lot more difference to action height than deformation down toward the bridge. I use a massive upper transverse brace, and L-shaped headblock glued to it, so the upper bout is completely rigid. Then the upper legs of the X and soundhole braces make the middle area fairly stiff (pumping the soundhole up and down isn't going to move much air anyway), and down toward the bridge is nice and flexible. Hopefully that will minimize the effects of long-term deformation, with minimal impact on tone quality. We shall see in about 25 years if it worked.

Double sides would probably help resist deformation, plus improve tone with the added mass. I'm just too lazy to build the forms to make them.

Another thing I've been considering lately is switching to a fully adjustable pivot joint. Most of the designs I've seen have an ugly gap (for example the Howe Orme style shown here http://www.nkforsterguitars.com/blog/my-favourite-guitar-howe-orme/), but having the action height as easily adjustable as the truss rod would be a big improvement. Hopefully I can come up with a variant that satisfies my aesthetic sensibilities :)
Author:  Trevor Gore [ Mon Apr 23, 2018 5:02 am ]
Post subject:  Re: Bolt down FB extension
DennisK wrote:
Another thing I've been considering lately is switching to a fully adjustable pivot joint. Most of the designs I've seen have an ugly gap (for example the Howe Orme style shown here http://www.nkforsterguitars.com/blog/my ... howe-orme/), but having the action height as easily adjustable as the truss rod would be a big improvement. Hopefully I can come up with a variant that satisfies my aesthetic sensibilities :)

Well, it can be done, Dennis, but I wouldn't want to deprive you of the challenge of coming up with your own design... ;)

Attachment:
DSCF7235s.jpg


Attachment:
DSCF7242s.jpg

The action height on this one is even easier to adjust than a truss rod, because you don't need any tools.
Author:  DennisK [ Mon Apr 23, 2018 9:06 am ]
Post subject:  Re: Bolt down FB extension
Does that have a perfectly fitted pocket cut into the body? That's pretty much what I was thinking, although I thought it might need some felt lining or something to prevent rattling between the sides of the heel and walls of the pocket since there's no glue or pressure there to prevent it. And to protect the finish on the sides of the heel since it will be rubbing against the walls of the pocket when adjusted.

I also figured a cantilevered fingerboard extension would be necessary... I take it there is an air gap underneath this one?
Author:  Dave Rickard [ Mon Apr 23, 2018 1:36 pm ]
Post subject:  Re: Bolt down FB extension
Trevor Gore wrote:
Well, it can be done, Dennis, but I wouldn't want to deprive you of the challenge of coming up with your own design... ;)

Attachment:
DSCF7235s.jpg


Attachment:
DSCF7242s.jpg

The action height on this one is even easier to adjust than a truss rod, because you don't need any tools.



Could I talk you into a little more detail on that
Author:  Trevor Gore [ Tue Apr 24, 2018 9:13 pm ]
Post subject:  Re: Bolt down FB extension
DennisK wrote:
Does that have a perfectly fitted pocket cut into the body? That's pretty much what I was thinking, although I thought it might need some felt lining or something to prevent rattling between the sides of the heel and walls of the pocket since there's no glue or pressure there to prevent it. And to protect the finish on the sides of the heel since it will be rubbing against the walls of the pocket when adjusted.

Yes, precise fitting is required. No need for felt, etc., but it is toleranced down to the last coat of lacquer. (Not as hard as it may sound).
DennisK wrote:
I also figured a cantilevered fingerboard extension would be necessary... I take it there is an air gap underneath this one?

Yes, again.
Dave Rickard wrote:
Could I talk you into a little more detail on that

Here's another variant on a cutaway classical:

Attachment:
DSCF9068cs.jpg

The adjustment is via the spin wheel you can just see through the sound hole. The concept is just an up-to-date variant on the old Stauffer system. If I ever get round to writing Volume 3, I'll put full build instructions in there. It's just router jigs and some hand fitting.
Author:  Alex Kleon [ Wed Apr 25, 2018 7:29 pm ]
Post subject:  Re: Bolt down FB extension
ImageImageImageImageImage

I came up with this after looking at a picture of Mr. Gore’s FB extension.

Alex


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