Braces To Be Tucked Into Lining The braces in the photo at right with circles at the ends are those that will be notched into the lining of the guitar. In this procedure, the end of the brace is trimmed down to a certain thickness, and a notch of corresponding depth is cut into the side of the guitar where that brace intersects the side. The top is glued onto the guitar, with the braces protruding into the notches. The end of the brace is trimmed flush with the side when the top is trimmed, prior to cutting channels for the binding and purfling. This particular step often gives beginners problems: It certainly did me! I believe I ve now found a method that will eliminate most of those, so that the inside of the guitar will be better looking, and more acoustically efficient. Circles show which braces are normally inletted or notched into the lining and side. Some luthiers do not notch the lower X-braces, feeling this frees the top. It s a subject on which you should do your own research and go with your own conclusions. Make A Couple Of Little Wooden Jigs The two small wooden tools shown at right, home made, are the secret. To make them or just one, since one will do the job get a piece of scrap wood about an inch wide and 2 inches long. Got your router yet? (Laminate trimmer is best.) Set a router bit (same one used for the center marquetry strip on the back will do it) for 0.1 inch and rout into your little piece of wood a.1-inch deep,.5-inch wide channel. (Leave your router set up exactly this way; do not remove the bit or change the depth setting! Later, we ll use it on the rim for a tight fit.) With doublestick tape, put 80-grit sandpaper into the channel. On the sides, put some additional tape: Paper binding tape or some other tape that sides easily. (Don t worry about the added tape and sandpaper thickness; they cancel each other out within 001.) The problem with notches in most beginners guitars is that the height of the brace ends don t quite match the depth of the notches. Usually the notches are over-sanded or over-filed, so that they are deeper than the braces. The top meets the lining just fine, but the notches show some unsightly gaps. By using the same router bit setting used to create the tools, the mismatch can be eliminated. With the flat end-cut router bit set for 1/10-inch, cut a channel in a bit of scrap: Add sandpaper in the bottom of the channel, but not on the sides. Tape on the sides lets the tool slide on the spruce top without scarring it. Sand only until the side rails meet the spruce, and you have a 1/10-inch height for the brace ends. Later, you ll cut a 1/10-inch notch in the lining and side of the rim. Back to the sanding tool. The reason for the tape on the sides is so that you won t scar the underside of the top. And, by making pencil lines for the trim line of the top, you will blur them when the tape rubs against them, indicating that you have hit the depth you want and you should stop sanding. (See 2nd photo from top; note the smudges.) At right: The result: A clean and nicely fitted job of inletting the braces. (We ll cover the lining notches later.) The fit inside the guitar will be good with this method. BUILDING MARTIN-STYLE ACOUSTIC GUITAR KITS 41
Trim The Brace Ends Before using the wood-and-sandpaper tools shown at left, trim the braces down with chisels. Be careful not to cut them down too far. If your trimmed shape isn t graceful enough, as in the second photo at left, use the chisel and sandpaper again to smooth the slope of the brace. Continue trimming and sanding until you have trimmed all of the brace ends. After sanding down to the 1/10-inch level, you can later chisel and sand to improve the contours of the braces. Remember, if you wish, you can cut the lower end of one or both of the X-braces so that they are not tucked into the lining and rim. The effects of this might be a slight bellying of the lower top, below the bridge, and a slightly louder bass response and overall volume. Do more research for yourself in the internet forums, etc., before deciding. Finish Basic Brace Shaping In the third photo at left, you can see that the ends of the braces are finished. The lower treble X has tape on the tip to remind me not to sand, file or chisel it. It s ready to go. A patch has been added to the X-Brace joint. This seals the end-grain of the wood and strengthens the joint where the braces have been dovetailed together. The patch is a cut-down cotton.22 gun-cleaning patch saturated with cyanoacrilate glue. Any type patch will serve the purpose of sealing the end grain. The additional carving done on braces is apparent: On this guitar, I scalloped the lower bass-side X-brace and the lower tone bar, but the treble-side X-brace was left straight. Dana Bourgeois, a noted and respected luthier (pantheonguitars.com), outlined this procedure at one point, and his guitars have won the Acoustic Guitar Magazine Readers Choice Gold Medals for overall tone. Though I know there s more involved in that than just these brace shapes, it can t hurt to imitate excellence! However, do your own brace research on the internet. There are as many ways to carve braces as there are guitar makers: The various theories and debates might make your head swim, but they will educate you, too. The top braces are basically shaped. To arrive at this point, some tapping has been done, but the final tap tuning will be performed after the top is glued to the rim. Now, on the back braces, we ll do the same braceend carving we did on the top, using the same chiseling and sanding method. 42 BUILDING MARTIN-STYLE ACOUSTIC GUITAR KITS
3. NOTCHING THE TOP LINING & SIDES FOR BRACES The brace ends of the top s X-braces and the shoulder brace need to be glued into the sides of the guitar, in order to help with structural stiffness and stability. This is the step that frequently gives novices fits, because it is easy to overdo it and make the notch deeper or wider than it should be. However, through the use of the sanding jigs (top photo, previous page), and with a measured cut into the lining and side, a better fit can be achieved. (Of course, if you are an experienced woodworker, this all probably sounds somewhat silly; to a novice, as this writer was at the beginning, it s a challenging skill to learn.) The outside and inside of the same braces after the lining has been notched. The overhang of the top will be trimmed off later. Matching the brace thickness to the depth of the notch is the trick. Basically, you are going to mark positions for notches in the lining, and cut them. Marking The Sides and Linings Insert pins into the two holes in the top and neck block, and align the centerline of your top at the tail end of the guitar. Secure it in position with rubber bands. Be certain that the top is centered; after the notches are marked and cut, the top will not change from this position. The bottom two photos show the same braces as the top two photos. The brace ends simply need to be marked on the outside of the body. Now you know why giant rubber bands was in the supply list. With a white pencil, carefully mark as closely as possible the point where the brace meets the outside of the guitar s side. As you can see in the top photo, this mark will determine the outside edge of the notch at that point. Mark all of the braces without moving the top. The shoulder brace, and both ends of both X-Braces should all be marked. Double check the marks to be sure the top hasn t been nudged during the marking process. If it has been moved, start over. The body is lit from inside by a flashlight. The upper X-braces, where they meet the lining of the upper bout, are at an extreme angle, lengthening their contact with the lining. This provides more stability. You do not need to mark the inside of the lining. (Normally, you don t even need to look at the inside right now.) Before notching, these are the same two braces shown in the top photo. BUILDING MARTIN-STYLE ACOUSTIC GUITAR KITS 43
The top can be removed after marking and double checking your marks. Copy the position of the side marks to the top edge of the lining, still along the outside edge. With your 24 straightedge, mark the corresponding edges across the body for each brace. You might be realizing that with this much measuring and marking, one inaccuracy or error can become magnified as you work, especially if another error is made. It is just important to recognize this and to take extra time to be certain of each mark s accuracy. After marking each notch es edges, because I ve proven to myself that I need all the reminders I can get, I fill in the space between the marks with white pencil. Cutting The Notches Recall that earlier (on page 41), it was suggested that you leave your router bit set for the depth used to make the brace-tip sanding cauls? Here s where you ll use it again. Using that same router and bit, with the bit depth unchanged, carefully rout the marked section of your lining. Don t hurry it. It is better to leave the notch slightly less deep than needed, than to get it too deep. After routing all of the notches, put the top back on and check the fit. It should be very close, almost right... The goal, as you know, is to make the notches the proper depth so that the brace ends fit snugly, and the top fits down flush onto the lining. The better the fit, the better the sound. The fit probably won t be perfect on the very first try, and you will need to do a little bit of filing. Work slowly, and your fit will eventually be perfect. Frequently, because of the way the kerfs in the lining line up, an edge or partial section of lining can break off. If you wish, take the time to replace it; however, it won t make a major difference in sound or stability. This flush-routing step isn t done until later, but here is shown the fit (after top is glued on) of the same two braces shown on the previous page. As you can see, the fit is snug and close, providing good support for the top and a stable, solid body. 44 BUILDING MARTIN-STYLE ACOUSTIC GUITAR KITS
Reducing the Back Braces For Inletting The back braces are done the same way as the top braces were done. Again, be careful not to chisel too far before switching to the sanding tool. The same method watching for the smudged pencil lines, works fine. On the darker wood, you can also see the spruce powder from the brace. When you start pushing it around with the taped sides of the sanding tool, you re at the right height. After getting the brace ends down to the correct height, sand and even out the contour of the braces. The sanding tool starts pushing dust away when the correct height has been reached; be sure it s even on both sides. Mark and Cut Notches for Back Braces The procedure for this step is exactly the same as for the top. After marking the brace positions with the back held in position by rubber bands, set the back aside and mark the notches with white pencil. I don t always mark the entire notch, although it does help with visibility. After your notches are marked, use a Dremel tool with base, or a laminate trimmer, with the same bit as before, still set to the proper depth. Here, the bit is set at 0.1 inch, same as the sanding tool used on the brace end. After you have cut the notches for each brace, put the back on again and check the fit of the notches. A little filing will make it perfect. Although your fit might not be as good as a factory job or as good as an experienced luthier, it will be very good using this method. Of course, it depends on your skill with your tools and your accuracy in measuring. If you re already an experienced woodworker, this will not be at all difficult and your fit will most likely be much better than that shown here. Mark the notches with a straightedge spanning the back, and a white pencil. Cut the notches to the 1/10-inch depth with a Dremel or with your laminate trimmer. Next... Gluing the Top Now that the notches are cut for the top and the back comes one of the major steps: Gluing the top onto the rim. Though it is not a difficult procedure, this is a step where problems can occur. (Text continues on page 50.) Check and fine-tune the notch depth by fitting the back and clamping. Should be very close! BUILDING MARTIN-STYLE ACOUSTIC GUITAR KITS 45