Tenon design for a double cut

[Phaedros]

Well... after completing my Junior build I´m contemplating on building another double cut - this time of my own design.

There is one particular problem I`m running into though. I don´t want to use a pickguard and it´ll have two pickups, so tenon length/ construction is an issue.
I´d love to go down the same route as I did on my junior but that would mean I could have a max tenon length of approximately 2" (s. below) - this would get me into´61 SG short tenon dimensions although my body is a good bit thicker than the spiky one´s.

The other solution would be to extend the tenon below the top I´d like to apply. That would introduce a whole different lot of problems though because I would either have to joint the neck before glueing the top or alter the tenon shape in a way that I can slide the neck under the top. Would dowels be an option?
I don´t want to alter the body shape to allow for a larger glueing area...

Any ideas?

 

[Freeman Keller]

Unfortunately that is one of the compromise of a double cut guitar and the need to push the neck joint so far into the body. I have repaired one guitar with a short tenon and frankly I would never build one. If you are doing a drop top you could route he tenon as far ino the body as you want, when you do the pickups the tenon will still be below the pups. And 335's are double cutaway guitars that don't have the problem, but then they don't have the fret access.



When this failed the owner "fixed" it by pouring five minute epoxy in the hole

 

[Telenator]

When I built this one I went overkill for sure.
The neck goes halfway back to the bridge pocket. Didn't want to take any chances.

 

[Phaedros]

@Freeman Keller thank you! Yes - if I get the terminology right - it’ll be a drop top i.e. a bound flat top.
I thought it might be possible to somehow index the already bound top in order to glue it after joining the body and the neck.
A bit like a bound fretboard maybe.
Do you think I should temporarily fix the top to the body, rout for binding, separate the two, glue the neck then the top?

This last picture you posted - must have been a nightmare to get it cleaned for a decent glue up!

@Telenator thank you as well! So did you basically route the neck into the backside and added a back „veneer“ to it? Basically a reverse top?
Gorgeous guitar btw!

 

[guitarbuilder]

No matter what you do, the tenon will be weak when it is cut by the pickup. Maybe you can consider a pair of flush mount pickups instead of a Gibson pickup? There are always tradeoffs from one decision to another.

GFS NYII Surface Mount Handmade Alnico Pickup

If I was determined to do a dc guitar like that, I might have the body meet the neck joint at a more advantageous fret.

 

[Phaedros]

@guitarbuilder good point - thank you! I designed the guitar for 23 frets and the fretboard to butt up directly with the neck pickup.
I‘m pretty much sold on soapbar P90s. They don’t require too deep of a cavity if I set the neck high enough and at an appropriate angle. Since I contemplate on having a floating bridge a la Gretsch this would add up nicely. (I know I‘m adding up one design flaw after another )
I wonder how PRS are getting their necks t hold up - having 24 frets and a fat humbucker route…

I plan this to be my first CAM build meaning lasered templates and maybe even some CNC machining (you basically spiked my interest with your current firebird build) while keeping everything else very traditional. I already joined the body and the two sides of the top using hide glue and want to abstain from any modern glue and finishes on this one.

 

[Freeman Keller]

@Freeman Keller thank you! Yes - if I get the terminology right - it’ll be a drop top i.e. a bound flat top.
I thought it might be possible to somehow index the already bound top in order to glue it after joining the body and the neck.
A bit like a bound fretboard maybe.
Do you think I should temporarily fix the top to the body, rout for binding, separate the two, glue the neck then the top?

This last picture you posted - must have been a nightmare to get it cleaned for a decent glue up!

@Telenator thank you as well! So did you basically route the neck into the backside and added a back „veneer“ to it? Basically a reverse top?
Gorgeous guitar btw!

OK, if it is a flat top that does make a difference. Depending on the bridge you choose you will either have to have some angle or the neck standing proud of the top by a little bit. The various Gibson flat topped guitars use a combination of these, Hiscock has a good description in his chapter on geometry. If it was my guitar I would lay out the side view with the dimensions of your bridge and get all that worked out. Most drop tops are right at 1/4 inch thick, that is the heigth of mose binding which just hides the seam.

The guitar in my picture is a 335 style with a carved (not flat top) but you can still see how the tenon goes as far as the edge of the neck pickup (which is right at the end of the fretboard). On a 335 the body joint at 19 on a 22 fret neck.

If I was making this guitar I would route the tenon before the top was on and run the route all the way to the bridge pickup cavity. Make the neck and cut the top down like in the picture, you can clamp the top on while you do your geometry stuff. Frankly it would not hurt if there was a channel between the top of the tenon and the bottom of the top - you need to run wires there anyway.

On set neck guitars I like to route the mortise and the final neck angle and make the bottom of the tenon flat with respect to the fret plane. That way you can make it too tall and lower by planing off the bottom of the tenon. It also makes fitting to the front of the body easier. I also do the binding channels and glue in the binding before I glue the neck in.

As far as the neck in the picture, the epoxy wasn't that hard to get out, it wasn't doing any good and just chipped out.

 

[Phaedros]

@Freeman Keller thank you again! So I‘ll make a scale drawing of the geometry first on paper and see how everything aligns, then work out the final templates. I have a week to go before I can actually access the laser cutter for the templates. This will leave me enough leeway to wrap my head around everything hopefully.
There‘s a lot of stuff to consider in this build and I can’t screw up on many parts because I want to use some fancy wood that would mostly be hard to replace.

 

[Freeman Keller]

I'm sure that you have seen my article about geomety - I believe everything starts there unless you have very good plans for exactly what you want to build. The bridge is critical, most Gibson style bridges will stand 5/8 off the top wat their lowest adjustment but make sure. As I said, Hiscock does address these issues and I do in most of my build threads. My cardinal rule is that the fret plane should just hit the tops of the saddles at their very lowest adjustment. There are many ways to get there and it really doesn't matter how you do it. If you don't actually have your bridge in hand at least get the engineering drawings from the manufacture or a vendor.

Looking forward to your build

 

[AAT65]

@Telenator thank you as well! So did you basically route the neck into the backside and added a back „veneer“ to it? Basically a reverse top?

That is how Rickenbacker 3xx’s are always made, which is what Telenator was referencing in his build… it’s a great engineering solution, all the routing and drilling is done to one piece of wood, the back is a very simple flat cap and - as he showed - you can hide as long a neck tenon as you want under there. the Rickenbacker design also uses this to make their tailpiece recess to get the string break angle over the bridge.

A fun fact which I keep on trotting out is that Telecaster Thinlines are built the same way. Not that it’s a coincidence — Roger Rossmeisl designed the Rickenbacker 3xx then joined Fender to design the Thinline.

 

[Phaedros]

@Freeman Keller yes I had seen and just reread it to refresh my memory.

Just for reference:

Building for playability

Geometry 101 I’ve been thinking about doing this thread for quite a long time but several recent threads tell me this might be the time. If any of you have followed my ranting, er posting, you know that I am quite focused on the geometry of the guitar. I frankly don’t care what your guitar...

www.tdpri.com

Great and detailed information - this will keep me occupied for a bit.

@AAT65 thank you - I had no idea about the special construction of the Rickenbackers and thinlines.


I put a couple of minutes into the research about PRS construction. Seems they use a rather short tenon that doesn’t fail as catastrophic as the early SGs did regularly.
I wonder if this is due to overall better fit and craftsmanship or because the SG also was a lot thinner and had even more material removed to facilitate the neck access. Might be a combination of both. Looking at the SG and inside the pickup cavities there are often pretty obvious gaps in the joint area.

Maybe I can take an offcut of my mahogany and do a test to failure before committing to the real thing…

 

[Freeman Keller]

Maybe I can take an offcut of my mahogany and do a test to failure before committing to the real thing…

All of the tests that I have seen of wood working glues in shear, the joint is stronger than the wood. Butt joints not so.

The joint in my picture had been seriously compromised - the sides had been finished before assembly.

 

[crazydave911]

Other than absolutely precise milling PRS also uses a little known trick. They model their neck joints after a classical, called a Spanish heel. By using a curved surface the bottom of the neck has substantially more gluing surface and are even inserted differently. There is a YouTube video somewhere of a neck being glued in at the factory. He swoops in a dipping motion after what looks like way not enough glue. In the end just enough squeeze out to clean

 

[Swirling Snow]

Remember, all systems have a fuse - a weakest link. Gibson protects their neck joints by having the headstock break off.

 

[badscrew_projects]

When adding a neck pickup to my Jr, I made the same compromise between the neck joint solidity and the pickup's distance to the neck as what Gibson did on their double cut specials. I didn't measure, just did that by eye and memory.

The pickup is farther away than on a single cut
Still, that's not a loot of wood holding the neck

 

[Swirling Snow]

I don't have any suggestions, just encouragement to persevere.

I do have a PRS Santana, the pickup frame is an inch from the binding on the bass side. It does not ring. Long tenons for the win!

 

[Phaedros]

@crazydave911
@badscrew_projects @Swirling Snow thank you! I’m still a bit indecisive which route to go. My delve into PRS construction kind of took away my fear of a sub par result using a tenon of comparable length.

On a different discussion board I found the following picture:

the perils of Gibson's short neck tenon

http://acapella.harmony-central.com/showthread.php?t=2202984 This is not a Gibson-bashing thread by intent. I really like their guitars and I adore my...

markweinguitarlessons.com

If you look at the first joint, it’s a wonder there were any that survived…

 

[guitarbuilder]

That short tenon is 3 inches long. The short tenon wasn't a problem until the internet came along . That is known as a rocker tenon for ease of installation. Notice the 2nd and 3rd one look like the same neck...;-).

 

[Phaedros]

@guitarbuilder thank you! I see, so another tyre kicker problem... I´m leaning more and more towards setting a geometry as close as possible as per @Freeman Keller ´s article and then rely on the joint I get from it without trying to improve on unimprovable things

I have taken the time to make a mock up of the lowest points in inkscape.

First is a completely flat layout of all components with pink being nut and saddle and blue being scale length. Light green is minimum heel thickness under the pickup of a bit under 1"

second is tilts applied as much as my wood will allow with dark green being the angle I´d get from a trapeze tailpiece over a floating bridge. Minimum bridge height in this case would be 20mm/ .78"

Main question here would be how much break angle is needed to keep a floating bridge in place? I´m not entirely set on a floater and trapeze but am kind of having a romantic implication towards thast combo

 

[guitarbuilder]

Another short tenon photographed... now with more wood surface....LOL I'm gonna guess that most of the popular hits of the 70's and 80's had short tenons in the recording studios.

Gibson Long Neck Tenon - Here comes trouble!

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