clamp

Top Separation Repair on 'Bowl-Back' Ovation

If your acoustic guitar top is starting to separate or lift a little from the guitar sides, it’s usually a reasonably straightforward job to repair.

Basically speaking, it’s a matter of some glue and some good clamping. Good clamping is the secret to all good glue jobs and it’s not too much hassle to clamp most acoustic guitar tops.

However, on a guitar like an Ovation—with a moulded, curved back—things are a little less cut and dry. Applying pressure along the edges of the top is a bit more tricky.

Hence, this monstrosity.

Crazy clamping on an Ovation

Crazy clamping on an Ovation

The guitar’s neck is held in my vice.

I’ve a couple of mats below to cushion it and conform to the shape.

The other side is held in place so it doesn’t start to ‘flip’ when I…

Clamp the top using my workbench as a clamping point.

This way, I can get a decent, downward pressure on the top so it’ll re-glue to the sides. We’re not talking tons of pressure here—this is a fine (if less than graceful) solution. 

Bridge Collapse

The saddle slot in some bridges is quite close to the front edge. In an ideal world, this might not be too much of a problem because, even though there’s a lot of tension from the strings, most of that is ‘downwards’ towards the bottom of the bridge.

Of course, it’s not an ideal world and, even though most of the pressure goes down, there’s always some that’s trying to tip that saddle forwards too. Things like the strings ‘biting’ into the saddle and actually pulling it forwards as you tune up can add to the problem.

And sometimes the bridge gives way. Like this.

The front edge of this bridge has sheared off

Now, I could just smooth off the fracture line and glue in a new piece but I don’t want to trust the glued joint to take that strain. It might be fine but I want to give this repair as much of a chance as possible.

So, I’m going farther back into the saddle.

My plan is to remove wood to the back of the saddle slot. I’ll glue in some new wood and then re-rout a new slot into that new wood. This way, the glue-line won’t be taking the strain.

You can see what I mean in the sketches below.

'Grafting' new wood to broken guitar bridge

New saddle slot will have new wood in front of and below

So, below is the bridge with the wood removed. I’ve sloped a section from the front of the bridge to the back, bottom corner of the saddle slot.

You can see the (slightly out of focus—sorry) shape of the piece I’ll be glueing in.

By the way, that’s just a thin piece of sheet brass that’s taped down to the guitar. It’s there to protect the top as I work on this.

The photo on the right below gives you a better idea.

New wood to be grafted on to bridge

New section will fit in like this

Clamping this one needed a little thought. As well as clamping downwards, I have to keep a pressure towards the rear of the guitar. That’s tricky though. I came up with this:

Inventive clamping to keep it in place

I clamped a block in place near the front of the bridge. The new bridge piece will bear off this and, as I clamp it down, this new piece will ‘wedge’ into place against the block. I can now get good clamping pressure in all the right places. Yay.

Once done, it’s just a matter of shaping the glued-in wood to the right profile and routing a new saddle slot.

I decided to make a new saddle too. The old one was actually an un-radiused classical saddle and it was made from a pretty soft plastic (the strings were digging in as mentioned above). A nice bone saddle will sound, play, and wear much better.

Hopefully, there's a long life ahead for this guitar. 

End-Block Crack Clamping

Cracks are never fun. This one's in an awkward spot, too. It was happy to close up relatively easily but it's a tricky location for clamping. 

Time for some out of the soundbox thinking (see what I did there?).

Side crack at end-block

Side crack at end-block

Cutting clamp to side contours

Cutting clamp to side contours

Cutting a block to match the curve of the guitar side in this area was an easy enough job. Now, I had my clamping caul and just needed a way to clamp. I drilled a hole through the caul. This allowed me to feed a bolt through the guitar's end-pin hole and through the hole in the caul. Snugging up the bolt pulled the caul in, closing up the crack.

Crazy block-clamped side

Crazy block-clamped side

Now, to the completely honest, I did add a long, sash-type clamp to give a little extra pressure to be completely sure about this. You can't put too much pressure on with that, though, as it'll start crushing things if you're not careful. The extra helping hand my bolt-clamp gave was just what the doctor ordered in this case. 

Oh, incidentally, that caul is lined with cork and then packing tape. Its slick surface means the glue won't adhere to it. Otherwise, after this repair was done, I'd have a completely new, Caul-Glued-To-Guitar-Removal-Repair to contend with. 

Repairing Loose Acoustic Guitar Braces

Visible gap on loose acoustic guitar brace

Glued inside the top and back of your acoustic guitar are braces. These are wooden support beams* that provide strength to what are, otherwise, relatively thin pieces of wood. 

Sometimes a brace can become loose. This could be because the guitar gets a knock but, often, some or all of the glue can just fail for a variety of reasons. 

A loose brace can be a pain. If part of the guitar isn't properly supported, it can pull and warp in unpleasant ways. That's generally not good. In addition, one symptom of a loose brace (and frequently the one that leads to its being discovered) is a nasty buzz or even a rattle when some or all notes are played. Often this buzz is located around a certain note (a tone or so either side) as the loose brace vibrates in sympathy. 

These can be an incredibly frustrating thing to track down. Sometimes you'll get lucky and be able to see the gap between brace and top/back (like in the photo at the top—the shadow beneath is clear) but, more often, you'll end up, up to your elbow in the sound-hole, poking at joints with a feeler gauge, trying to find a tiny gap. It's a real pain. 

When it's found, the gap should be cleaned and the old (failed) glue removed. Then, fresh glue is worked underneath the brace and the repair is clamped up to cure. This sounds straightforward until you try doing it, at the limit of your reach, blind (or, with an obscured reflected image in an inspection mirror).

Loose acoustic guitar brace

Find loose guitar brace

Not so with this one, though. These are back braces and they're relatively easy to get at. This particular guitar did actually get a knock and has had a previous repair for a back/side separation. I can't be certain that these braces were knocked loose at that time but it seems likely. Maybe not, though—benefit of the doubt for the previous repairer.

You can clearly see the feeler gauge poking under the braces in the photos. The blue tape is something I've put in, by the way. It keeps the mess down when working glue under the brace. 

Once there's a good smearing of glue in there (and it needs to be worked well under to get a good joint), a bit of a wipe up, and then it's clamped (see below). The little scissor-jack thing is a god-send for these jobs—it gives decent clamping pressure and I can wind it up from outside the sound-hole. 

On this particular instrument, this has to be repeated a few times as I found four loose ends. But not any more more. All re-glued and sorted. 

Glueing and clamping loose back brace on acoustic guitar

*I think 'beam' is the correct structural term for guitar braces but any engineers can feel free to correct me. Beam tends to make most people think of massive steel joists, however, while guitar bracing tends to be a little smaller. And wooden. 

Neck Correction: Back-Bow Baby

It's certainly been mentioned a few times around here that the strings on your guitar exert quite a bit of tension on the neck. Enough, usually, to pull the neck into a 'bow' shape (with the middle being farthest from the strings). Our trusty truss-rod can generally be called on to counteract that tension and to control the bow or even straighten the neck completely against the string pull. Sometimes, however, we get what's referred to as 'back-bow'. With a back-bowed neck, that bow shape is effectively reversed and the middle has ended up closest to the strings. This means that a note fretted in the lower end of the neck can't sound clearly as it hits off the 'uphill' frets all the way to the middle of the bow.

There are dual-action truss-rods available and these are able to correct for back-bow as well as, the more normal, forward bow. They're becoming more common but lots of guitars still have the usual single-action rods that can only correct forward bow to counteract string tension. As this is what it needs to do in 99 out of 100 cases, that's generally fine.

But sometimes it's not.

guitar neck relief correction

Setting up this guitar, I found it was back-bowed beyond the point where string-tension would have corrected it. Open notes and those as far as the eight fret or so all choked or buzzed. Even with the truss-rod slackened off completely, the neck wouldn't pull straight or into relief (a very slight bow).

There are a number of things that could be done to try to address this, some of them relatively involved jobs. Before getting into those discussions regarding what isn't really a super-expensive guitar, I had a punt at a quick-fix. This doesn't always work and isn't always suitable but it's certainly worth a go in this case.

In the first photo, I've got my heating blanket sitting on the neck, weighted down by a heavy fret-leveller. I don't want to go nuts with the heat here. Too much will just cause hassle in this case but I'm applying sufficient heat to slowly heat the glue holding the fingerboard to the neck. I don't want it to completely let go; just to soften slightly.

correct back bow on guitar neck

When I think it's where I need it to be, I clamp the neck into a bit of a forward bow and leave it to cool. If things go to plan, the glue will re-harden and help the neck to hold some of the shape I've forced it into.

And, luckily, things went to plan. Unstrung, the neck now has just the slightest of back-bows and, under string-tension, that pulls into a little relief—enough to get it playing nicely again.

Incidentally, a workplace safety tip: Even if you are fully aware that this procedure will leave your steel fret-leveller in a very hot condition and, even if you wear heavy gloves to move it, you shouldn't put it over to the side of your workbench, right where your elbow will touch it when you're checking clamping pressure. That would be stupid.