A little ways back, I discussed the removal of an acoustic guitar’s neck for repair. I also talked a little about my opinions on the construction of that particular guitar. The neck-removal post was getting a little long so I decided to split out the reassembly part.

Putting an acoustic guitar back together generally involves some glueing. Sometimes more and sometimes less.

A bolt-on neck will generally just require that the fingerboard extension (the part past where the neck meets the body) be glued to the guitar top while the bolts inside will handle the job of pulling, and securing, the neck into the body.

A dovetail neck joint requires this but also needs glue in the joint itself. Depending on the manufacturer, the face of the heel (the flat portion that butts against the guitar side) may be glued too. Some guitar makers (Martin, for instance) don’t apply glue there while others (Gibson for example) glue it. This is one of the reasons it’s a bit more work to perform a neck reset on a Gibson.

In the case of this particular guitar though, the heel face is entirely flat and is all a glueing surface. The steel box-section tenons must also be glued into their corresponding mortice (channel) in the top and the fingerboard extension must be fixed to the guitar top.

Complicating matters is the fact that there is no force that would pull the neck into the body in the same way as a dovetail or bolt-on joint would. This means I had to clamp the neck into the body in some fashion while the glue cured.

Some inventive clamping-caul making later…

And I had a wooden caul that would fit the curved heel, letting me clamp the neck into the body. Ready to go. I did a couple of dry-runs with no glue as this was a tricky clamping job. When I was happy I could get the clamps on quickly and accurately, I went for it.

That clamp in the photos—running from the soundhole to the heel—wouldn’t normally be required but this instrument’s construction made it necessary. The clamp doesn’t actually contact the soundhole edge but I’ve got a piece of linoleum there to play it safe.

Once the glue’s properly cured, it’s ok to unclamp. I replaced the fret I removed (see the previous post) to help steam off the neck, made sure it was secure and level and I strung this little fellow up to make sure it played well.

This job was a little more involved than it might be on a different guitar. All that’s not important though. What’s important is that this guitar is making music again. That’s always good.

Cross-posted to Guitarless

In a previous post, I gave my opinion on what I saw as the problems with the neck-joint design of a guitar I’d recently worked on. I thought you might be interested in some more detail about that repair (without my whinging about design issues). While some of the steps undertaken in this repair are common with any job that involves removing a guitar’s neck, you might find it useful to, first, check out some of the ways in which this guitar differed.

The guitar had taken a knock and its neck had become detached at the heel. It still appeared to have some attachment towards the guitar top but it wasn’t easy to see what was going on. Internally, there was quite a small neck block—too small to accommodate a dovetail—and no sign of bolts although the feeler gauge I inserted seemed to indicate something bolt like. It actually took a chat with the manufacturer’s customer service to sort it out. There were no bolts or dovetails—dowels were used to align the neck and the joint was a mortice and tenon.

Fixing a problem like this on a guitar isn’t just a matter of squirting some more glue in and hoping for the best. A proper job requires that the joint be disassembled and cleaned. If this isn’t done, the new glue will not penetrate properly and will only adhere to the older, failed glue rather than to good, strong wood.

Removing an acoustic guitar neck involves softening whatever glue is holding the neck to the body. A dovetail requires holes be drilled into the joint so that the glue can be softened by carefully injecting steam. That’s not required for a bolt-on neck, of course, but what is common with all joints—including this one— is that the glue holding the fingerboard extension to the guitar’s top be loosened. We do this by applying heat.

Sometimes that heat is applied using a cast block that I heat on a hotplate. For some jobs though, I use heating blankets. These are much more controllable but you still need to take care. The blanket is clamped—loosely—to the fingerboard extension and I keep a very close eye on it. When I judge that heat has penetrated the board and begun to soften the glue I remove the blanket and get to work with the palette knives. It’s a delicate job as too much pressure could easily tear into, or lift grain from, the guitar top underneath. It’s often necessary to heat the area a couple of times to separate the surfaces.

Once the fingerboard extension is loose, the neck removal can begin. As I mentioned, on a bolt-on this is an simple as undoing some bolts while a dovetail would need the joint steamed loose. On this neck, removal was complicated because of the construction.

You can see from the images that the neck has two steel box-sections protruding from the heel. These were glued into the corresoponding channels in the guitar top. I needed to get this glue to soften too but the heating blanket wasn’t going to do the trick. It was necessary to use a similar technique to that used for dovetail disassembly. I removed one of the frets on the extension, drilled a couple of small access holes and injected steam (very carefully—these are small channels very close to the guitar top).

This process, too, was made more difficult than on a traditional construction. Because of the alignment pins, I could not remove the neck from the body vertically. Instead, I needed to ‘pull’ the neck away from the side. It made for an annoying job as it’s really hard to get any leverage or apply pressure well.

—o—

As this is becoming a little long, I’ll cover reassembly in a future post. Oh, the suspense…

Cross-posted to Guitarless

I should definitely preface this post by stating that what follows is my opinion only. It may be that I’m alone in these views or it may be that other guitar builders and repair-techs agree. The post below, however, is my take on things.

I recently had a Tanglewood TW130 through the shop for repair.  It’s a nice little acoustic—I’ve always been a sucker for all-mahogany acoustics. The guitar had taken a fall and the heel had come away from the body. I’ll detail the steps taken to assess and repair this damage in a later post but I wanted to discuss the guitar’s construction as a separate issue.

Before I get to that though, a little primer on acoustic guitar neck joints. Bear with me…

The Traditional Dovetail Neck Joint

Historically, acoustic guitars had their necks fixed to the body with a dovetail joint. This is a very strong joint and when glued is damned solid. The dovetail is considered the ‘traditional’ neck-joint and it tends to be more prized by many who consider it imparts a superior tone to the guitar. A good dovetail joint tends to require a little more work and care to accomplish well though, and it makes for a little more work when performing a neck-reset on an older guitar.

The Bolt-On Neck Joint

For these reasons (and possibly others), many modern guitar makers use a bolt-on neck joint. In this joint, a short mortice and tenon is cut in the neck block (in the body) and in the neck. This is used mainly for alignment purposes although it provides some strength. Most of the joint’s strength, however, comes from the bolts that are attached, through the neck block, into threaded sockets in the neck heel. These tighten to pull the neck securely into the body and, questionable arguments about tone aside, provide a strong, solid joint. And, when it comes to setting the neck at some stage in the future, it’s much easier to undo some bolts than it is to steam out a glued-in dovetail.

The New Neck Joint?

This Tanglewood doesn’t use either of these methods, however.

This guitar has a quite small neck block (the part that the neck usually bolts or dovetails to) and has a slightly larger than usual support under the fingerboard extension. The reason for this latter is that there are channels cut here to accept the truss-rod (in the middle) and two square, box-sections of steel on either side.  It’s these steel sections that—glued into the channels on top of the guitar—that provide the bulk of the joint’s strength.

You can see three dowels poking out the front of the neck block/body—one of these is wooden and two are plastic. In my opinion, their primary role is alignment as they’re not going to provide much support.

The face of the neck-heel—where it butts against the body—is a glueing surface on this guitar and I guess this was considered sufficient support when combined with the dowels and channels. I’ve a couple of problems with this.

• String tension does a mighty fine job of trying to pull the headstock of a guitar down to meet the bridge. Poor support along the heel area can only make this job easier. Think of a long-bow. The tension of the bow-string pulls the bow into that arched (bow) shape. That’s what the strings are doing on your guitar too. The poor thing needs all the help it can get to resist those damn strings. One knock was enough to break the (slightly brittle) hold this glue had.
• Dovetail and bolt-on neck joints both pull the neck snugglyinto the body. As well as strengthening the joint, this can only help tone and string energy. The Tanglewood’s neck is, effectively, sitting on the body with a bit of glue and a couple of pins holding it in place.
• While it’s fair to argue the practicalities of the owner of a lower-cost guitar deciding to plump for a neck-reset at some stage in the future, should that happen, legitimately disassembling this sort of joint would (perhaps counterintuitively) be much more problematic than what was achieved with a simple fall in this case. As it happens, reassembly is more difficult too.

Now, I’m not being elitist here. This is not a guitar that cost thousands and there are many valid reasons for manufacturers to economise where they can. I’ve owned, played and repaired many cheapies and budget instruments in my time and many have been absolutely fine (and some have punched brilliantly above their weight). I’ve no idea how much money was saved in the manufacture of this instrument in this manner rather than with a regular bolt-on neck and I’m slightly conflicted in passing judgement as it’s great the there is now such a selection of fine instruments available for peanuts. It certainly wasn’t the case when I began playing guitar.

Personally, though, I can’t help feeling that the decision to go with this joint over a regular bolt-on has compromised this instrument. At very least, I feel it’s durability, and therefore longevity, is compromised. I don’t think that’s a good thing on any instrument, no matter how much it costs.

What do you reckon?

Cross-posted to Guitarless

You’ll often hear musos talking about a neck reset (or neck set) on acoustic guitars. As this is something that tends to be required on pretty much every steel string acoustic eventually, it’s worth understanding why it happens and what’s involved in a neck reset.

The top of an acoustic guitar is under a lot of stress. String tension exerts quite a pull on it. Over the years, the wood of the guitar top succumbs to this tension and begins to belly a little at the bridge. This effectively raises the bridge and, with it, the action or string height along the neck. As the guitar ages, it becomes harder to play.

The solution is usually a neck reset. The neck is removed and some wood is removed from the heel to modify the angle at which the neck joins the body. This basically alters the geometry of the neck/guitar to compensate for the higher bridge. It’s a pretty big job but one that most acoustic guitars will need at some stage in their life (when depends on a lot of factors) if you own them long enough.

If you think your guitar’s action has been (very slowly) increasing over a number of years, you might have a candidate.

I’ve written an article for Guitarless outlining the reasons and the neck reset process so feel free to take a look – it goes into a bit more detail.

Incidentally, if you’re considering buying a used or vintage acoustic, it’s worth asking if it’s ever had a neck set (which is a good thing if it’s been well executed) and/or checking if the guitar needs it. If it does, you should factor that into your bargaining process as it can be a relatively expensive job.