Convert Your Flat-Top into an Acoustic Lap Slide

January 6, 2006

Requiring only a few basic hand tools, it’s a fairly easy project that costs less than 20 bucks, including a fresh set of strings. Toss in a grooved tonebar, and you’ll be in business. If you decide the world of Hawaiian-style overhand slide isn’t for you, the conversion is quickly reversible. Chances are, however, you’ll dig having an instrument that opens the door to funky licks and grooves you can’t duplicate with bottleneck technique.

Fig. 1 shows the slotted, arched extension nut and bone saddle blank you’ll need for this project. If your local shop doesn’t stock these items, you can get them from online luthier supply outfits or folk-music stores. Prices vary—at, the metal nut costs less than $4 and the saddle blank is about $6. A bone saddle blank provides excellent tone, yet is easy to cut and shape. Bone blanks have a straight top, which puts the strings on a flat plane to match the playing surface of your tonebar, and are almost a half-inch tall. Before you go dashing off to acquire these parts, a little homework is in order.

Bone blanks generally come in two thicknesses—1/8" and 3/32"—so you’ll need to determine which size fits your guitar. First remove the strings, and put the bridgepins somewhere safe. Next, carefully remove the original saddle. With a little coaxing, it should pop out, but if the saddle acts stubborn, pad your guitar top with a few hand towels, and use a pair of pliers to gently rock the saddle out of its slot. If the fit is really snug, use an object with a narrow, pointed metal tip (like a dental tool) to slowly pry the saddle up from one end of the slot. Save the original saddle in case you want to reconfigure your guitar for fretting. Now measure the saddle slot width, as in Fig. 2. If the gap falls between 1/8" and 3/32", buy the thicker 1/8" saddle, and plan to shave off a little width by rubbing the blank lengthwise along a piece of fine sandpaper. Once you’ve got your saddle blank, you have to trim it lengthwise. Measure the saddle slot, mark the saddle (Fig. 3), and use a small hobby saw to remove the excess length. Take your time and watch your fingers.

Saddle shaping comes next: To prevent the string windings from separating and the plain strings from snapping, you’ll need to put a gentle slope in the saddle’s rear (bridgepin) side. Start rounding the back edge with a small, flat file (an automotive ignition file is perfect for the job), and then smooth your work with fine sandpaper. You don’t have to remove much. The goal is to keep the saddle’s top perfectly flat and maintain a crisp right angle on the leading edge (which faces the soundhole). While you’re at it, round off the two upper corners so they won’t poke your picking hand. Fig. 4 shows a finished saddle: The strings climb across the slope and then leave the saddle precisely at its leading edge. These angles resemble the top of a capital “D”—perpendicular on the front and curved on the back.

Hey, we’re almost done. Now slap a set of medium-gauge (.056, .045, .035, .026, .017, .013) acoustic strings on your guitar. Tighten them a bit so they’re basically aligned, but leave enough slack so you can lift them up to slip the extension nut over the guitar nut. The metal nut will hang over the sides of the neck—that’s okay (Fig. 5). Center the extension nut, drop the strings in their respective slots, and then add tension to both outside strings to hold the new nut in place.

Finally, tune up the guitar. Most lap sliders use open-D tuning (D, A, D, F#, A, D), but open G (D, G, D, G, B, D) is another sweet option. Don’t worry if string tension shifts the arched nut slightly to one side or the other, that’s normal. After your guitar settles in, and you sense it can handle a little extra tension, try increasing the gauges of the second and first strings—the two plain ones—to .018 and .014, respectively. This increased girth helps support the tonebar and adds more whoop-ass to your melody notes.

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