Official Luthiers Forum!

Thanks for the additional info, Bryan!

Really? The extension end moves toward the sound hole? What does this look like and how does it or how can that happen? Guess I am not clear because I don't even glue or fasten the extension and "never" seen the relationship/distance between the sound hole edge and the extension change.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Ha! I've been spelling it wrong all this thyme!

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

My current fave neck joint is: Butt joint, walnut dowel through the heel (glued with HHG), brass inserts glued in with CA, furniture fasteners.

Has anyone else noticed how much gluing in a dowel changes the sound and apparent sound transmission of the neck? I know that may sound unbelievable, but try it. It's not subtle. It might be different if using PVA and soft mystery wood dowels.

I don't use hangar bolts but I seem to remember that they have a slot head in the machine screw side and that would make it possible to remove through the sound hole with a flat head driver?

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For any of you that use the dowel method do you have a video or pictorial tutorial on that?

I'd like to hear more about this. I have never noticed because I have never added the dowel to a neck that already existed so I don't know what it sounded like before. Can you describe the difference? How guitars have you done this to?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Seems to increase sound transmission. IE, if you tap or put a tuning fork at the 1st fret area, it can be heard more clearly at the heel end. Also, the whole neck gets louder WRT ring/tap tone. The last guitar I made with that kind of neck/dowel has very consistent sound up the neck, and somewhat excessive finger noise. (might be partially due to black walnut for neck material)

I didn't do it to a complete neck. They were 90% carved and had no fretboards when dowels installed. I tap on things a lot when building.



Well, two so far, so not exactly a scientifically meaningful sample size! I wouldn't have mentioned it, except that the effect is fairly dramatic and obvious.

This seems to fit into the discussion --- Older Taylor's

http://www.frets.com/FretsPages/Luthier ... reset.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

meddlingfool wrote:
Aluminum and brass.


I love the look. Was it difficult to get them level with the fretboard binding? Whenever I think about doing this, I worry that the dot and binding will sand unevenly.

If it was hard, I wouldn't do it...

Ken, that's exactly what I did and why I like it.

I can see it now... Dowels glued into dove tails for superior tone

I kid. I've never tried it so I don't know but forgive me for having strong reservations about that.

Having said that, but for my case mostly for marketing purposes, like the Frets.com link that Ken put up you can see that Taylor routed out the heal such that it's convex and only touches along the very edge of the contact with the sides. IOW the center is hollowed out. I built a guitar for a very good classical player who was very concerned about the bolt on joint VS the traditional Spanish joint. I convinced him that there is full heal to body contact just like a Spanish joint perfectly flush. It made him happy. And who knows it may have better tone because of it. But I doubt it.

I have been using the double tenon Bourgeois joint as described by John Mayes and Sylvan Wells for 9 years. Before that a bolt-on neck with a glued extension. They DO move more. I think the reason is that there is almost no top glued to the headbock with the large Bourgeois style mortise the the headblock can rotate more easily.

My guitars would go out looking great but when I saw them back at a year or so the action had frequently come up a 32nd or so due to a small change in the neck angle from what I think is headblock rotation because of lack of support in sheer. A minor neck re-set which goes quickly fixed it and they were stable after that. I didn't like it. I had not seen that with a glued extension.

I discussed this with Sylvan who had seen the same thing especially in cutaways. I found that Dana leaves a gap between the top brace and the fretboard mortise when the top is glued on and afterwards wedges in a filler strip to push on the headblock. His top brace has beefier ends and they have extra support.

I did this plus making the mortise smaller to allow more top to be glued to the headblock as well as reinforcing the mortise block edges for more rigidity and adding a 60' radius to the upper bout which I used to leave flat.

I have been doing this a couple of years and it has made a big difference. I still think they may settle a little more than a glued extension but it's a lot better. I don't consider it totally solved but am trying to avoid internal struts etc if possible.

Here's the newer mortise. After I cut it the gap is exposed between the mortise block and the top brace and I can wedge in a filler strip tightly and run in some thin CA.



Here is the fretboard tenon.



And the reinforcing of the edges of the mortise block.



One thing I have seen in a guitar that was over humidified with both a high output Oasis in the sound hole and two case humidifiers was slight warping of the end of the fretboard which is largely unsupported. I would worry a little about that in a guitar that simply has an unsupported extension lying on the top with out being glued.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Terrence, I found the exact same thing. Though I don't personally feel it has much to do with how much surface the head block has. If anything,,there is more surface glued with the paddle that supports the fingerboard.

I think it comes down to shear strength.

In any case, I was finding brand new expensive guitars were out of whack very quickly. No biggie if addressed, a ten minute fix, but, I was finding clients simply didn't see it. They perceived a loss of enjoyment without having an idea as to why. And, as they were starting to go far and wide, this was unacceptable to me.

So I went back to glueing the tongue. Easy peasy.

I had planned on experimenting with an adjustable set screw going through the UTB into a brass cap in the fingerboard tenon, and then I had this brilliant idea, which was to say 'meh'.

Yeah, I've thought about going back to a glued extension a few times but I think I am on to something now and they seem quite stable. Actually if you rout the big Bourgeois/Mayes style mortise in the headbock and headbock extension you remove much of the wood of the extension and I found it to weaken it significantly. You could make it thicker but then there is not enough room for the top bolt. The top is only glued to a small edge of the headblock and extension after that big mortise is routed. Even less in cutaways.

We'll see--- The ones I have done with the mods are not local and I have to track them down but talking to the owners they say things are holding fine. I did find the same thing you did. I'd see one back earlier and the owner would say he loved it. I'd see that the neck had moved a little and fix it and there would be this amazed look on their face and they would say something like "My God it plays so much better".

I may well be back here in a year gluing the extension.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Terence and Ed, I have also been using the double bolt on tenon on my guitars. I have not experienced the movement that you have. I do some small differences, I make the headblock and paddle as one piece and fit it tightly to the UTB and glue, and I support the other side of the UTB with beefier soundhole braces...this transfers any tendency to rotate to the sides via the main X.

I kept one OM for my self, almost 4 years old and no movement.

Here is a pic of my headblock again, the only downside is the 5/8" of end grain that the side is glued to which could be eliminated by fitting the paddle into a rabbet...

Chuck

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No worries. I respect your skepticism, and usually have a similar view on such matters also. I am more than skeptical of the electric guitar tone obsessed dudes and their irrational ideas. For example, the idea that if a neck isn't so tight it needs to be hammered into its slot with a mallet, the guitar won't have any magic mojo...

Anyhow, not saying that it's good or bad, just interesting that gluing in a walnut dowel made noticeable changes. I'll try a brazilian rosewood dowel next time, for extra magic...

Thanks Chuck. I always used a separate mortise piece tightly butted against the headblock and wedged against the top brace. I just recently started beefing up the soundhole bracing. Your mortise extension is definitely thicker than mine too.
Food for thought.
Thanks again
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I've not had any problems with this style of double tenon.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I think the mahogany insert that extends into the neck really helps with that, as it eliminates the 'hinge' effect. I'll likely use that on future deluxe guitars, but it's too much work for our budget boxes.

I really like that fully supported fretboard as well Trevor. I assume the upper bout angle has to be perfectly co-planar with the planned neck angle and if you wanted drop off you'd have to sand it into the fretboard

I do have your book but don't recall seeing how much movement you get with string tension i.e. how much gap you shoot for over the bridge unstrung with your system.


Ed I have definitely seen a "hinge" effect at the neck body joint with the separate tenon and have made my upper bout angle a little less than the ideal neck angle to compensate for that. Lots of variables to juggle.


Lots of good ideas here.

Thanks

Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Check out McPherson

http://mcphersonguitars.com/technology/

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Ken Cierp

http://www.kennethmichaelguitars.com/

Trevor's dual tenon certainly is doable for the small shop. Even with CNC equipment Taylor's profile heel pocket design is a challenge (I have experimented) the neck heel itself was troublesome for me, you take it a fraction too small and its scrap.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Section 4.6.12 in Design, "Neck angle, neck relief and top curvature". Few texts do a good job on this subject. I don't know another that discusses the interrelation between relief and neck angle, for example.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Trev, thats why they don/t discuss it, very tricky to get it right.