Featured Restoration - The Screws & Holes

Screws & Holes

Hi Guitar Players,

It is a common knowledge that women worry a lot. I think it is equally true for guitar owners, especially the guys. They really know how to worry about their guitars… well this is a story of those worrying guitar guys out there.

Structural repairs made up the majority of my guitar services. Such repairs are very important and they should be carried out before other forms of repairs like functional and cosmetic. For this blog, I shall focus on re-gluing lifted guitar bridges of acoustic guitars.

The paper trick

Braces design of Small Acoustic Guitars

Re-gluing lifted bridges of acoustic guitars used to be rare. I didn't have to do too much of it until the dawn of "small sized" acoustic guitars. Many big brands jumped into producing such small guitars because they are very popular among youngsters. Small and light, great for lugging around whilst commuting.

In the aspect of volume projection, it is a basic logic that smaller guitars are not as loud as regular sized guitars. For musical instruments, volume projection is a significant indicator of quality. The designers overcome this barrier by "lightening" the bracing design on top boards by numbers. With the bracing design lightened, the volume projection was retained.

How do I know? Just toss a mirror into your small guitars, snap some pictures. Do the same to your regular sized guitars. Compare the pictures. The differences are obvious.

Guitar braces are like the pillars and columns of our houses. They give structural rigidity and stability to our roof and walls. In acoustic guitars, the braces on top boards function like house pillars. In additional, they also regulate the tonal qualities of acoustic guitars. Contemplate removing a few columns in your house… the same effects would apply on acoustic guitars as well.

In my blog post "Guitar Myths #002 - Are acoustic guitars' tops really flat?", I mentioned about the unavoidable bulging effects about acoustic guitars' bridge areas. If the regular guitars are suffering from this bulging effects, how much more would it affect the smaller guitar?

Bridge Lifting; How did that happened?

Many reasons contribute to bridge lift. In this blog I would be illuminating the structural rigidity of acoustic guitars' top boards, specifically small acoustic guitars.

As discussed earlier, small acoustic guitars' give volume projection more weight than structural rigidity of their top boards in design. One could easily imagine that when bulging effects set in, small acoustic guitars' top boards would get more of it. Another words, their top boards should bulge more than regular sized acoustic guitars.

Analogy of bridge lift

All new guitar bridges are made with flat base. They are glued to new acoustic guitars' top boards which were flat before loading strings on them. As bulging sets in, the curvature of the top boards increase. Invariably, the base of the new guitar bridges remain flat while the top boards changes in curvatures. As soon as the bridges could not keep up with the curvature (see picture above), the extreme ends of the bridges detached from the top boards. This detachment would appear like the bridges have lifted to our naked eyes. When left unchecked, the detachment grows until the guitars are unable to be tuned, or the bridges get ripped off.

Re-gluing Small Acoustic Guitars' Bridges; 2 Screws 2 Holes

There is actually no difference between re-gluing small acoustic guitars' bridges and regular acoustic guitars. However the difference in their respective life-spans cannot be more obvious. I have enough returning customers coming back for the same repair job, that is re-gluing small acoustic guitars' bridges that set me thinking of approaches to make this repair job more enduring.

A while ago I repaired a guitar that was of non-wood composition. Its bridge has detached and I made 4 attempts but they were in vain. Each attempt I tried a type of glue but nothing seems to work. The client was thankful for me trying that hard, at the same time he was very disappointed with the small guitar in question. He left that guitar in my shop.

Screws & Nuts; There is no better way than fastening the bridge to its top board by screws and nuts. So I picked up that guitar and placed screws and nuts on them. See right picture. Directly under the bridge and the underside of the top board, a piece of 3.5mm thick hardwood was glued onto the existing bridge plate as reinforcement. The nuts are secured onto the hardwood. I would like to emphasize at this point; the lifted bridge has already been re-glued properly before the screws and nuts get installed.

Since I have freely received this guitar, I too gave away this guitar freely to a deserving friend. I haven't heard anything regarding bridge lift since the guitar was given away.

Tone Affected?

Yes, FAQ from the worry guys. "Would drilling 2 mounting holes for screws and nuts affect my guitar's tonal quality?

What do you think? Personally, I have 2 replies to the above question, a simple and a elaborated one.

The simple reply; "No." Period.

The elaborated reply; "Would it affect the tone? Firstly there is one big hole in the middle of your guitar, plus another 6 smaller ones beneath your bridge pins. Adding 2 tiny holes wouldn't amount the slightest degradation to your guitar's wonderful tone."

Some small acoustic guitars use dowel pins for bridge positioning. For such design, there are already 2 tiny holes drilled onto the top board (see above picture). I simply make use of these 2 holes for my Screws & Nuts approach.

Admittedly, the Screws & Nuts approach may not be a popular solution to acoustic guitar owners. It is nevertheless an effective approach to give life-span endurance to your small acoustic guitars. Don't let the fear of unknown stop you from trying, instead take a rational view when deciding the most suitable repair jobs. Drilling your acoustic guitars isn't always bad.

Featured Restoration - A Hole on TOP

Once in a blue moon, some interesting repair jobs will walk through my door. I call this one " A Hole on TOP." Both the repair process and the remuneration for the repair were equally interesting.

Ripped Top

I received an email requesting for a repair job on a acoustic guitar. The owner has attached a picture (right) in the email for illustration.

When I seen it, I must say that I felt sorry for both the guitar and the owner. As you can see from the picture, the bridge of this guitar was completely ripped out of its footprint and part of its bridge plate has given as well. The owner has stowed this acoustic guitar within its case for… a pretty long time. So remember, play your guitars!

The owner has consulted other guitar repair techs but they have turned down his request. It was not surprising because this extent of damage required a lot of attention and effort. I think the other guitar techs didn't wish to spend too much time or effort so they simply use the most diplomatic response, "it can't be repaired."

That didn't discourage the owner to seek alternate opinions.

Most repair emails I have come across focuses on the cost of repair. This owner was more insightful which I later found out the reasons. He asked for my evaluation instead. It was an opened query, so I provided my inputs in these aspects, repair procedures, duration, possibilities and estimated cost.

I think he was delighted with my evaluation. In his email reply, he added a few more possible topics for me to ponder. On top of that, he suggested an interesting barter trade deal. Very uncommon in today's info-age.

He revealed his past experiences in making violins. It wasn't too hard for me to connect the ways he was evaluating my expertise and his experiences in wood working. As for my repair charges, it was a barter trade with his woods and tools. To a wood and tool junky like me, the offer was hard to ignore.

I was invited to drop by his place to check out his stuff. They are good stuff indeed and our barter trade was sealed. Cash isn't KING in everything, at least in this case.

The owner has been forthcoming in providing suggestions on how to reinforce the affected area so to prolong the lifespan of this guitar. I guess it was due to his experiences in violins making. The suggestions were also helpful in many ways.

Staring at the gaping hole, where should I start? In summary I have taken the following steps to repair it.

1. Inspect the guitar for other loose parts.
2. Remove existing bridge plate
3. Make a new rosewood bridge plate
4. Glue up all crack lines and delaminates found about the affected area
5. Reinforce through cracks with cleatings
6. Glue up new bridge plate
7. Make bridge footprint
8. Glue up the bridge footprint
9. Re-glue bridge
10. Re-drill bridge pin holes
11. Set up

Bridge Plate Removed

These steps were logical and pretty complete. But it didn't make it any easier.

I started with inspecting the guitar for other structural issues. Fortunately I didn't find any. So I went on to remove the leftover bridge plate that was still attached to the guitar top. It was easy for one half but the other was persistently stubborn.

A heated spatula was used however the spatula sliced into the thickness of the top plate and exited from the top. It was not something desirable however the show must go on. I persevered and the existing bridge plate relented eventually.

I went on the make a new bridge plate out of Rosewood. It has to be thicker and larger to take up string tension when the guitar gets set up later.

Many bridge plates were made with tow common considerations; conserving materials and light weight. For mass produced guitars, it was necessary to control material costs. Reduction to both thickness and size of bridge plates were the most logical approaches.

Bigger Bridge Plate

Likewise, I have two considerations as well but they were directly opposite. Jeffrey Yong has taught me to keep it big and weighty but not excessively heavy. So I made it filled up the apex space formed by the cross braces and stretching beyond footprint of the old bridge plate. You can see it from the picture.

So why did I go opposite? Jeffrey's perspectives about bridge plate were likened to the swing of pendulum. In order for a string to oscillate for a long time, a suitable weight must be added at the end. The top plate receives vibration from strings. As long as the top plate vibrates, sound is produced. It is then logical to find ways to prolong this vibration. With adequate inertia, the top plate should vibrate (oscillate) for a longer time. Hence the logic of having weighty bridge plate.

For guitar makers who maintain a light weight top plate, they do so because they believe that light top plates are more responsive. There are reasons that support this idea and equally there are as many reasons that would oppose it. It is not possible to ascertain which is a better approach because guitar making isn't a competition for the best. May the best ear decide.

Existing Cleat

The force which ripped the bridge out of the guitar has inflicted other damages to areas immediately around its bridge. Two crack lines that ran with the wood grain starting from both corners of the bridge were visible. These cracks can potentially grow longer as such they must not be permitted to propagate further.

From the picture on right, the existing cleat was exposed. That means repair work has been done on the area. Small portions of the top plate was lifted from the existing cleat and that has to be re-glued. A new cleat was needed to arrest the other crack. I made it from spruce and it has to be oriented cross grain to the top plate to maximize its holding effectiveness. The next few pictures showed progressively the steps needed to arrest that crack.

Crack lines arrested

Due to the extensive damages, certain repair jobs required clamping on the top plate. Inevitably clamping marks will be inflicted. The challenge was to minimize them. The next two procedures involved clamping on the top plate. The portions of the top plate that were sliced whilst removing the old bridge plate required re-gluing. It was time to re-glue the new bridge plate to close the gapping hole as well. Both jobs were carried out simultaneously.

Rosewood bridge plate clamped

The next job was a bit tricky. The ripping force has also torn away a portion of the top plate. It has taken the shape of the bridge's footprint. From the picture directly below, you can see the the new Rosewood bridge plate was exposed. In order for the bridge to be seated properly, a layer of spruce is required to fill that foot print. I selected a small piece of Adirondack spruce and made it into the shape of the foot print, and also the same thickness as the top plate. The grains has to be parallel with the top plate. The next few pictures showed in steps the making and gluing of the spruce foot print.

Spruce Foot Print

Spruce Foor Print Clamped

Spruce Foot Print Glued

Most of the difficult jobs have been completed at this stage. I went on to give the guitar a good clean up and a light buff. Re-gluing of the bridge came after that.

I left the bridge clamped overnight and allowed the glue to cure for the next 24 hours. The moment of truth has arrived, to put strings on the guitar. After all, the guitar was in my shop because the bridge was ripped out. While I have done my level best to get the bridge back to where it was, I wouldn't rule out the possibility of it coming out again. I was very cautious as I tensioned each string.

Fortunately, the bridge held up. However it was indeed a short moment of anxiousness. The guitar was finally set up and it played well and sounded fine. Finally it is finished!

Guitar Set Up

The Bridge Glued

Thanks for reading this far!