Bracing the Soundboard

Arguably one of the most important things for the tone of a guitar is the bracing layout. It is a very rigorous process that takes some time to complete but really makes a difference in the tone of the guitar. Bracing a guitar refers to a system of wooden struts that support and reinforce the soundboard and the back. We do this in order to strengthen and stiffen the soundboard, while keeping it as light as possible.

The first thing to do was to thin down the top of the guitar. Since I am using a hardwood as my soundboard, I needed to thin it down a little more than I would if I were using Spruce. The top for the parlor guitar is approximately 2 mm. To do this, the piece was just sent through the drum sander for multiple passes until the desired thickness was reached. Next, it was time to mark out the top bracing pattern. This is a traditional parlor bracing pattern. You can see how the braces are drawn on with pencil. When you look inside the sound box of a guitar, it is very common to see stray pencil marks, especially on the soundboard.

The next step is to start preparing the X-brace. The X-brace is the largest brace and bears most of the 150-lb tension that are applied to the top by the strings. The braces will all be made out of Spruce. The wood must be quartersawn with little run out of the grain. The picture to the left shows the X-brace, which has been created by two separate braces that have been notched out to form a 90 degree angle.

Once these braces are built, the they fit together and are completely flat, it is time to glue them to the top. Some guitars have a very large radius to the top. Typically this is roughly a 25-foot radius and it helps to focus sound. Additionally, the slight arch in the top can help to prevent caving and bellying of the soundboard under the great deal of tension from the strings. Due to the size of the parlor guitar, a radius is not necessary. Therefore, the X-brace is glued in on a flat surface. You can see in the picture to the right, the braces are glued down using fiber glass rods on a shop built go-deck, which gives equal pressure across the entire brace.

After letting the glue set up and stay in the deck for about an hour, we are able to take the soundboard out and leave it be for a few hours so. The form is then cut so that there is just a small amount of excess wood that over hangs the actual top of the guitar. This will be taken off when we glue the sides on.

Next it is important to take some of the stock off the spruce so that it allows the top to vibrate. To do this we take a chisel to the ends to form a scallop. This reduction in the ends of the braces allows for there to be more vibration towards the rim of the guitar. Additionally, it is believed that this helps to bring about more low end response. There is a lot of argument between scalloped and non-scalloped braces. Luthiers have their own styles and own beliefs. I personally have played many guitars with and without scalloped braces and they all have their place. For this guitar, I chose to stick with the plans that are outlined by LMI.

Next, I took down the edges of the braces using the same chisel so that they begin to look more like a triangle. Again, this is just taking away some of the rigidity of the braces which allows for more vibration of the top, this giving more sound. By shaping the braces, a luthier can tune the top so that it has optimal tone.

Finally, the last bit for the day was to glue in one of the cross-braces. This brace was shaped slightly prior to glue up. however, much more shaping will be completed, and there are many more braces to be added.

This last picture just shows some additional detail of the X-braces that have been slimmed down. There will be additional amounts of work completed on these braces, but this is just to get a start on all the work inside the box that needs to be done.

Starting the Process

So, here we are, two guitars and almost one uke completed and now I was set to begin another. But I needed to find the right materials. I started looking around online trying to find some nice wood that could be used for a smaller guitar. I looked through all the normal luthier websites and through other places that are normally not used by luthiers, when I came across http://www.curlykoa.com/. I was able to find some great looking pieces but all relatively expensive (as all Koa woods are). I was hesitant at first, this was going to be a pricey ordeal. However, I decided to bight the bullet and by some pieces, sight unseen. When the wood showed up at my door, I was floored. I purchased a top, back and side book matched set will all AAA curly koa. The wood was amazing, so much figure! I was extremely excited. I really need to give some props to Steve at curlykoa.com, he has a great selection. Now it was time to get started.

At the mill, we began the process by gluing up the book=matched top and back. This process is done by jointing the edges of the book-matched pieces, so that there is no gap between the two pieces. We then put a bead of yellow glue between the pieces and place them into a wedge clamping jig.

After letting this set for a few hours, we are then able to start working with the top and back to begin building the sound box of the guitar. We then bring the top and back to the drum sander, where we sand out all the glue marks and the saw marks from milling the wood. This also allows us to set the thickness of the wood.

The first thing to do is to begin the process of setting up the rosette. The rosette on an acoustic guitar is a way a luthier can decorate the top, using strips of material inlaid in the wood surrounding the soundhole. For this guitar, I decided to prepare a three ring rosette, using strips of black and white wood strips on the inner- and outer-most rings of the rosette and blue paua abalone in the middle ring. First a 1/4" hole is drilled at the center of the rosette, which allows for a routing jig, which allows circular cuts to be made in the wood. I first routed the center ring to glue in the abalone. Since abalone is a type of shell, it is a little different to inlay as compared to normal wood inlays.

To do this, after the routed channel was cut, we sprayed some shellac into the channel, to close the grain of the wood. Then, we placed the abalone into the channel and applied some CA glue, which seeped into the gap to glue the piece into the wood. Here is a picture of the abalone inlay. In this picture, you can see the 1/4" hole in the center and the beginning of the innermost channel. You can also see that I added a piece of white fiber on the inside and outside of the abalone.
While routing the innermost channel of the rosette, we had a slight malfunction in the router, the router bit broke and we had to put the tool away until a new one came in the mail.


Once the bit came in, I was able to rout the inner and outer channels and was able to inlay the white-black-white fiber. This was glued in using yellow glue as is typically done with rosettes. Finally, once everything was set, i cut the sound hole out using the same routing jig.

Now I know that it doesn't look complete due to the unfinished area at the top of the rosette. This is normal, as the fingerboard will cover this unfinished area.

Next on the docket, will be starting the bracing of the top and the back. I will be back when this process begins.

Previous Work

Hey All! My name is Kevin and for the past year I have been working with Daniel Collins at http://www.danielcollinsguitars.com/Daniel_Collins_Guitars/Home.html to build a custom made Bogdanvich classical guitar. The guitar is all hand built using a Bearclaw Sitka Spruce Top, Paduk sides and back, mahogany neck, ebony fingerboard, bridge, and binding, with herringbone purfling.
 
The way this all happened was by my father, Mark. He decided that he wanted to do something special for me as I was planning on graduating from the University of Illinois at Urbana-Champaign with my master's in science in kinesiology. He thought that it would be a great idea to build a guitar for me as I have been obsessed with guitars and music since I was a kid. However, he began building the guitar too late to be able to complete it by the time that I had finished my thesis. After about a year of work on the guitar and another 5 months of finishing work (lacquer), he finally finished the guitar. It is an all hand-built small jumbo, using a Sitka spruce top, walnut back and sides, mahogany neck, ebony fingerboard and bridge, and bloodwood binding (body, fingerboard).
  The guitars are beautiful to look at and even more amazing to play. The sounds that these guitars produce are simply perfect. The one flaw in the plan is that I don't play much classical guitar, but i am continuing to learn. Also, the small jumbo is a little large when you are sitting to play. But we will get to that shortly.

Recently, I began working on a ukulele with Dan which is in the finishing stages of completion. Just some small work that needs to be completed then I will be French Polishing the uke within the next few weeks. The uke is made out of ovangkol for the top, back, and sides, with cocobolo fingerboard, bridge, and binding. Here is the most up-to-date picture that I have of the uke.

It is looking really good. However, similar to the classical guitar, I do not play much ukulele but I will definitely learn a great deal when this baby is completed.

So this whole luthier thing came out of the blue to me. I never expected to start building stringed instruments, but when I started bending the wood and shaping the neck, I realized I actually really enjoyed the process. Yes, there are some really difficult experiences, and some very stressful times. But it is a really fun process. Therefore, I have found myself in a predicament. My guitar was completed, and the uke is pretty close to being finished, and I was worrying about trying to figure out what I was going to be doing on Monday evenings and Sunday afternoons, along with the occasional Thursday afternoon (the days that I work with Dan at Shady Lea Mill). Well, I continued to ponder the situation and continued to play my new instruments, when I came across a new guitar that C.F. Martin Guitars was producing, the Custom 00 Masterbuilt All Koa guitar (see http://www.musiciansfriend.com/guitars/martin-custom-00-master-koa-koa-acoustic-guitar/481882000010000?src=3WFRWXX&ZYXSEM=0&CAWELAID=197338629). It got me thinking, maybe a smaller guitar would allow me the freedom to play at all times (sitting, standing, etc.).

The one issue that I had with building my instruments, was that I was an absolute idiot when it came to documenting the process. I vowed that if I decided to continue on with my luthier work, I would make sure that I took pictures of the process. So that is where we stand now.