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Saturday, June 27, 2015

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!

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