Bending the Sides

The next step in the completion of the body of the guitar is the dreaded "bending of the sides." I say that because I think that I have been more afraid of this step than any other. Everything that I know about wood tells me that it's not suppose to bend and it's sure not supposed to get wet. But all the books and videos seem to reassure me that it's not a big deal. Well wer'e about to find out. In my research most of the information suggests a jig that is used to hold the bent pieces while they cool and dry. In the bending instructions on the StewMac website there is a picture of a simple two sided rack made from MDF and dowel rods. Before I start bending, I need to build something like that to hold the bent sides. I started with a piece of 3/4" MDF large enough to accommodate half the body size. I used my original template and traced the guitar shape on each side so I could place the dowel rods above and below the line to hold the bent sides between the dowels. I marked center positions above and below the traced line and drilled 3/4" holes with a forstner bit. I also cut another piece of MDF to use as the base. I glued the upright piece of MDF to the base and secured it with several biscuit joints. While the base and upright glue was drying I cut 3/4" dowel rods into 8" lengths. I put a little glue on the center of each dowel rod and inserted them into the drilled holes on the upright MDF. Simple and easy construction and it should hold two bent sides.

Finished bent side holder.

End view showing both sides.

Details showing template line.

OK, I guess I've stalled as long as I can, let's start bending. One of the first tools that my son, Brenan gave me was an electric bending iron. This is basically a pipe with a closed end mounted on a wood base. The pipe is wired with a thermostat so the pipe heats up and the temperature is controlled by the thermostat. The idea is with moisture and heat to create steam that softens the fibers of the wood allowing you to slowly bend the wood to the desired shape. Simple right. . . let's see. I literally spent hours and hours, days and days researching this process. I watched at least a dozen videos and read and re-read all my books. I finally decided to go with the instruction sheet that came from StewMac. It said to soak the wood in hot water in a shallow trough or the bath tub. It said that different woods needed to soak different lengths of time and it said that some woods didn't need to be soaked at all, just spritzed with water from a spray bottle. It suggested for maple, the easiest bending wood, that a soaking time of 30 - 45 minutes should be all right. It said and I quote, "It's hard to over-soak plain straight grained woods." I had purchased some practice bending sides from StewMac with the idea that I would practice with these and if they turned out I would just use them on this first guitar. The critical part I missed in the catalog was that these practice pieces of wood were exactly the same wood, the same thickness and width as the sides that came in their back and sides packages but not the same length. The first step before bending was to measure your template with a flexible rule or a piece of string and transfer the overall length and where the bends would be onto each side. Opps these sides were too short, dang! More delay, I decided to look locally to find some nice maple that I could resaw and sand to the right thickness for my sides rather than ordering and waiting longer for shipping. That turned out to be a great decision and was much cheaper. OK, now I am really ready to start bending. It was Friday night and I didn't have anything to do so I started with the short practice pieces and soaked one side in hot water for about 30 minutes. While the wood was soaking I clamped the bending iron to my work table and turned on the iron and set the temperature to 6, the recommended setting. I started bending at the waist as suggested and found after a few seconds on the iron with a lot of sizzling and popping the wood started to relax and I was able to bend it. I worked for a little over an hour and had difficulty in getting the tight curve at the waist. I decided to stop and start on the real thing the next morning. With the new wood I had purchased I had an extra side so, surely I could get two good bent sides out of the three pieces of wood. I started on a Saturday morning about 9:00 am. I filled my trough with about 6 inches of hot water and put my new side material in to soak for the recommended 30 minutes. I began bending about 9:30 on my first side. I worked, and worked, and worked. At about 1:00 my daughter brought me a cheese sandwich, which I ate in about three bites and continued to bend. At 3:30, I was so tired and frustrated I quit in disgust! The problem wasn't bending -- I could bend the wood easily but I couldn't get it to stay bent. The wood also looked horrible by this time. It was scorched and almost a green tint from all the water. I clamped it in my solara, not my new holder, and used every spring clamp I had to make it conform to the right shape. I hoped that when it dried it would retain the correct shape. That evening after I had recovered my composure I started looking on-line for help and answers. I found a chat forum dedicated to luthier questions and techniques. One post was asking for help and advice with exactly the same problems I was having. He was using the same wood, maple and he soaked his wood for an hour before beginning. There were at least six immediate replies with the same advise. Don't soak your wood! His response was exactly like mine. . . but the instructions said. . . Their response was unanimous, I don't care what the instructions said, don't soak the wood.  Use as little water as possible. Try a spray bottle and just mist the wood. Use an old wet towel and place it over your bending iron so the wood never touches the metal. The heat from the iron and the moisture from the towel make the steam and there is less chance of burning the wood. Sunday, I checked my clamped up piece and it had dried and it did retain the shape but it was so overworked it was fuzzy and worse it was twisted. I started over using the new technique on the last practice piece and it worked much better. I quickly decided to try the new technique on the last two pieces of maple. Between the new technique and clamping up the hot bent wood in my make shift mold I was able to get them bent. Hooray!

Bending iron clamped on the work table. The template to check progress is behind.

The pipe is thinner on the bottom for tighter curves.

First failures.

New technique with wash cloth. I thought the monogram added a touch of class.

Bending!

Trying to get the feel and technique down.

Using the stainless strap to help retain the heat and moisture for smoother curves.

Bending the tighter curve at the waist.

Clamping the hot side into the mold.

Clamped left side in mold.

Clamped right side in mold.

After the sides cooled and dried I was finally able to put them in my holder.

  What I learned, my first fears were indeed founded. It was harder than the books and videos make it out to be but with a lot of patience and the right techniques it is possible. Like most things the more you do the better you get. I will definitely build or buy solid molds for the drying forms for my next guitar rather than using the adjustable solara that I built for this one.

Bracing the top and back

The next phase of construction is bracing the top and back of the guitar. Remember, the top is made from spruce, a very soft wood. The final thickness of the top is planed down to approximately 1/8". This is a very thin structure to support the tension of the strings in the completed guitar. The top must be braced with thin ribs of wood to help support the tension. The back is a little harder and more dense wood but it is also very thin, approximately 7/64", slightly thinner than the top. It also must be braced to support the ultimate tension and stress of the strings. The wood most commonly used for the bracing is spruce or red cedar similar to the wood used for the soundboard. I did not have enough spruce  left from the top to use for braces and as I mentioned before there are no local suppliers of this type wood. Matthew suggested that I use some furniture grade pine that he had. The pine was light and soft like the spruce. It was also straight grained but it did have some knots that had to be worked around. I started cutting it up into the appropriate widths and lengths while trying to cut around the knots. I cut enough for all the braces and then cut long strips that I would later use for kerfing support when I attached the top and back to the sides.

Before I finished the braces and attached them to the top and back I had to decide how I was going to clamp them on while the glue dried. I also had to figure a way to make them slightly curved to match the radius on the top and back. Although the common name for a steel string guitar is a flat top guitar, there is nothing flat about it. Most guitars have a slightly curved top. This is achieved by shaping or hollowing out the face of the solara about an 1/8' and matching that arc on the bracing. The back has an even greater arch which is achieved in a similar manner. A large number of wide throat clamps would have to be used in attaching the braces or a clamping system called a go-bar deck could also be used. Since I didn't have either I decided to make a go-bar deck. The go-bar deck is a simple device consisting of a flat base with a top attached about 24" above the deck. The top is separated by four corner posts about 24" long. Strong flexible go-bars are cut from hardwood slightly longer than the 24" space between the base and the top. These go-bars are flexed and placed between the top and the base of the deck creating even pressure down on the glued brace. This clamping system was the easiest of all the jigs to build and has been a huge help in gluing up components for the guitar.

Go-bar deck gluing up the center brace on the back.

More go-bars on the center brace.

Detail of go-bars clamping the center brace, notice the cross braces used as spacers.

I arched the back braces on the belt sander to a template I created to keep the arch consistent. I traced the template on to each brace using a center line to keep the placement uniform. I then carefully sanded to each line, trying to keep each arc smooth and uniform.

Arch template for back braces.

I also arched female forms on wider wood strips using the same arch template. I mounted these female counter forms on a flat particle board base that would be placed on the base of the go-bar deck below the back to help transfer the arc of each brace and curve the entire back.

The arched female forms aligned and attached to the back glue up board.

Closer view showing the arch and the center line.

The arched back board, the back and the braces in position to glue on the go-bar deck.

The go-bars applying pressure to the first brace.

The go-bars applying pressure to all of the braces.

A closer view of all the go-bars and braces.

One of the advantages of the go-bar system is the ability of gluing all of the braces at one time. Even with enough wide throat clamps it would be impossible to glue and clamp all the braces at one time. Generally you would glue one or possibly two braces at a time let them dry and glue the next two. In a couple of hours I am ready to  finish shaping the braces with a block plane, chisels and then sand them smooth. Even though most of this bracing won't be visible the craftsmanship is very important for the final tone quality of the instrument.

Roughly shaped braces glued in position.

Shaping the braces with a block plane.

Finishing the shape with a chisel.

Final sanding.

At this point most of the books suggested that I start tapping the back and front to check for tone quality. So, I did. It sounded like a piece of wood being tapped. Seriously, I have no reference to what the sound should be so I am going to assume it is great and move on. The next step was to basically do the same thing with the top. The brace placement for the top is quite different than the back. The top or soundboard has more impact on the tone and sound quality of the guitar and the brace placement is essential to that tone quality. All of my books and all of my plans called for a standard Martin X brace system. There were slight variations in each of the plans. I decided to go with the original plans I started with from the Internet. I cut each brace and rough shaped it with the band saw. I used my solara that I made in the beginning as the base to transfer the radius to the top. I also used the solara and the washer technique to transfer the solara arch to each brace, then carefully sanded each brace to match the arch line. I marked and glued them in position using the go-bar deck.

The go-bar deck gluing the braces to the top.

Closer view of the X pattern, notice the hole in the center of the top brace.

The neck will have an adjustable truss rod in it and a hole for access to this adjustment had to be drilled in the top brace directly above the soundhole. The adjustment nut takes a 5 mm allen wrench, so the hole had to be big enough to allow the wrench to easily go through.

5/16" hole for truss rod adjustment.

Top with all braces glued in position including the bridge support.

Close up showing the X brace and delicate support braces.

The fit for the X brace proved to be one of the more challenging aspects of this project. It is a simple lap joint. I have done this type of joint many times and thought it would be no problem. This particular X brace was not 90 degrees. This was a bigger problem than I thought but it is structurally sound and no one can see it in the finished guitar, so I'm good. The back and top turned out well and are beautiful works of art in their own right.

More Research and Books

About this time in the process I felt I needed more input and another or better source of information. I had received a gift certificate from Barnes and Noble Books as a gift, so I thought I would add to my reference material. The book title that I kept seeing as a reference in many of the on-line videos and blogs that I had been researching was "Guitarmaking Tradition and Technology" by William R. Cumpiano and Jonathan D. Natelson. So I went to the local Barnes and Noble book store to see if they had a copy. They didn't, so I ordered it on-line.

Third book for reference.

When this book arrived I jumped into it the same way I had the previous two. It was slightly larger and after reviewing all three I think this book was the most complete. The authors wrote about building both a steel string guitar, like I was building, and also a classical style at the same time. This was a little confusing especially when trying to find information later about a specific construction technique. Again, I would have to say the logical and best thing for a first time guitar builder would be to pick one source and stick with it. I would probably recommend this book as that single source with one exception, the neck joint. I will talk more about that later when I get to that part of the construction. This book is not quite as visual as the other two, no color pictures and the black and white images look a bit dated but the information is solid and more detailed.

The sound hole and rosette

Now that the back and top had both been successfully joined and cut to shape, it was time to focus on the task of cutting the sound hole and inlaying the decorative rosette rings that surround the sound hole. This would be my first attempt at inlay and I was a little worried about this delicate process. I knew I would need an attachment for my router or my Dremel tool to cut the circle shapes. I did some research and found a variety of attachments were available for either tool. I found a really nice looking circle attachment from Stewart MacDonald to fit my Dremel and decided the smaller tool seemed like a better more controlable tool for this job. The sound hole/rosette routing jig from Stewart MacDonald was a well-crafted aluminum and brass jig that attached to their Precision Router Base attachment for the Dremel. I had purchased the router base earlier when I first started acquiring special tools to make the guitar. I had some 2" aluminum bar stock and after some consideration I thought I could fabricate a similar circle cutter attachment. I quickly sketched out some rough plans and consulted with Matthew about the construction. He also thought we could make this attachment, so we began. It was a fairly simple 2 piece device that used a sliding center pin to adjust the size of the circle. The hardest part for us was cutting the slot in the aluminum. Matt suggested that we try a straight spiral router bit chucked up in the drill press and mount the aluminum bar on a sliding machine head clamped to the drill table bed. This method was a little rough but worked. I used an old 3/16 drill bit and cut of the shaft to use as the center pin. A small thumb knob and bolt purchased at the local hardware store was used to secure the sliding mechanism at the fixed radius for the circle cuts. Two small flat head allen screws were used to attach the jig to the router base.

The aluminum base with slot and counter-sunk attachment holes.

The two aluminum pieces and the center pin.

The completed circle jig.

The circle jig with attached Dremel tool.

Close up of jig, center pin and Dremel attachment.

Now that I had a method of cutting circles I could start cutting the rosette rings around the sound hole and the sound hole itself. I thought that I could use a regular Dremel 1/8" router bit to cut these rings and the hole. I had one so I chucked it up in the Dremel and attached the new jig. I got a couple of scrap pieces of wood to experiment on and drew out the circle patterns with a compass. I adjusted the height or depth of cut on the router base to approximately 1/16" and made my first cut. It was horrible! The edges were soft and fuzzy and the bottom of the cut was not square. This would not work. The StewMac catalog recommended a down cut spiral, solid carbide bit for this but I thought surely I could find a suitable bit locally and not have to order another expensive bit and pay more shipping. So, I started searching. My first stop was the local lumber/home improvement store. The bit had to be a 1/8" shaft to fit my Dremel tool. The Dremel section at the home improvement center would surely have a bit that would work. As I suspected they had a ton of bits and accessories for the Dremel tool but very few actual router bits. They did have a 1/8" solid carbide spiral up cut bit rather than the recommended down cut bit. I thought to my self, this would work, it might even be better and it was half the price. NOPE! It was just as bad on the edges but it did have a flat bottom. Well, to make this story a little shorter, I tried several more bits all with no better results and ultimately ordered the bit from StewMac. It arrived and of course worked great. So, after a test cut, I began on the spruce top.

Routing the rosette circles with the Dremel and circle jig.

Detail of cutting the rosette rings.

Removing the cut sound hole.

The finished rings and sound hole.

The rosette rings around the sound hole are purely decorative. In my research and in the books that I am working with I found many different and beautiful examples. I decided that on this my first guitar I would try and keep it simple. Most steel string guitars have a series of very thin black and white stripes. These are usually made from either very thin wood strips or plastic strips. My first thought was to go with plastic strips that I could order from StewMac. These plastic strips are cheap and pretty easy to work with because they can easily bend and conform to the circle inlay. After calculating the amount I would need to go around the circumference, I checked the StewMac catalog. I found that it was going to cost more than I thought. I noticed that they sold a pre-bent set with a beautiful herringbone pattern for a lot less than the total cost of the plastic strips. That seemed a no brainer, so I ordered it and some plastic strips to later bind the body. They fit nicely in my routed rings. I learned that you start your cuts and later your inlay work on the top of the circles. This part will later be covered by the finger board if you make mistakes or if your inlay material runs short. This was the case with mine but the finger board will cover it when I attach it later in the construction.

Dry fitting the rosette.

Dry fitting the outside and inside rings.

Applying glue.

Pressing the rings into the routed channels.

Trimming the ends to fit.

Finished rosette.

Detail of herringbone