Best Way to Bracing Guitar Neck After Gluing Easy Way

Tonewoods

Body Size &
Style

Bracing

Sides

Neck & Tail
Blocks

Neck

ACOUSTIC
GUITAR
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Article

"Howard, that will surely end up in a famous musical instrument
 museum one day .... What a cool guitar!"
---Dan Erlewine

Every guitar I build is a one-of-a-kind, custom instrument. I have no standard model names or numbers. I work slowly; my output is about 10 guitars each year. I build as much as possible from raw materials, including making parts that many builders buy ready-made, such as liner blocks, fretboards, bridges, strap buttons, and purflings. I design and make my own marquetry purflings (the well-known "herringbone" is one example of marquetry). Your Klepper guitar will be truly handmade, by one set of hands: my own.

It is common for custom builders to make guitars in batches of several guitars at a time. The builder will use dedicated jigs and fixtures, and each operation is repeated as many times as there are guitars in the production run. This saves time and increases output, but it moves custom building in the direction of factory building. The guitars may differ in the end in their trim details and combinations of woods, but so do the guitars built by the factories. The price of increased production is decreased individuality. I work on my guitars one at a time, and do not have more than two under construction--in different stages--at any time. This allows me always to be attentive to an instrument's unique qualities. It also allows me to keep feeling that my work is fun. I didn't get into this in order to create a job for myself working in a factory. If I wanted that, I would be working in someone else's factory, with fewer worries, and for a higher wage. I like to build guitars "on spec." These are instruments not ordered by customers that I design to try out ideas and to satisfy my creative wishes. When they are done I usually place them for sale with a selected retailer. Before a spec guitar goes out to a retailer, you can purchase it from me directly, and avoid waiting for a custom order.

There is a lot that is out of the ordinary about my designs and construction methods. I will go into some of the details on the following pages. You can skip to a topic using the links on the left of the page.

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Tonewoods

At present I build with tops of Swiss European spruce (picea abies or picea excelsa--the names are interchangeable), Adirondack red spruce (picea rubens), or western red cedar (thuja plicata). I have used Sitka spruce and Engelmann spruce, and while these are reliable woods, I think that in general their tonal potential is a bit lower.

There are of course exceptions to this, and many fine guitars have been made with these top woods. But I think there is a better chance of making an outstanding guitar with the woods I use, and outstanding guitars are my goal. When I come across particularly good tops in any species, I will consider them. For example, I have a few master grade tops of Caucasian (Oriental) spruce that I think have great potential. I also have a small number of European spruce tops that were imported from Germany in the 1950's (all native European spruce is of the same species, but the spruce cut in Bavaria, which has been virtually unobtainable for the past 40 years, is considered by some to be superior).

While the top wood is much more important to the tone of a guitar than the wood used for the back and sides, these parts do make an audible difference. I have a wide selection of back and side sets that I have selected and seasoned in my humidity controlled shop. Besides the more commonly used woods--East Indian rosewood, cocobolo, mahogany, walnut, koa, and maple--I have sets of several species available that are not frequently used. This may be because of their limited availability, or just by historical accident, but all have the potential to make first-rate guitars. These include osage orange, African blackwood, Tasmanian blackwood, brauna (also called Brazilian ebony), Gabon ebony, Ceylon satinwood, zebrawood, bloodwood, ziricote, bocote, pernambuco, and others. I also have some sets of Honduras and Madagascar rosewood, and a good selection of Brazilian rosewood that was harvested prior to the ban. The choice of back and side woods will affect tone, but the differences between some woods are slight, and there will be overlap of the natural variations in properties among two or more species. For this reason, a good portion of the choice in back and side woods can be made on aesthetic grounds. I have quite a bit of experience using multiple woods in combination, which greatly expands the woods palette.

There is a tendency when people talk about guitar woods to refer to the tone of this or that wood, or of a particular wood combination. For instance, people may ask, "What is the sound of a koa body with a cedar top?" as if the species of wood is the main determinant of the sound of an instrument, and any two guitars made with this combination will sound similar. I firmly believe this to be false. The design of the guitar and its excecution by the builder are far more important. Woods do have a tendency to contribute to tone in characteristic ways. This varies greatly with the individual board, and even more greatly with how it is used. It is more meaningful to talk about the sound of a certain size and design of guitar, as made by a particular builder--without even knowing what woods were used--than the sound of a certain combination of woods. The choice of woods will be one element that affects the sound, but only one.

A word about tonewood grading: The last few years have seen a lot of "grade inflation" in the tonewoods business. Thirty years ago, the highest grade was AAA. Then some dealers began to distinguish especially good sets with an AAAA or Master grade. Most of the older, established dealers have stayed with that system. But recently many other wood dealers, and some guitar companies, have tried to distinguish their woods with new grades that may be confusing to both guitar makers and guitar buyers. The most important thing to understand is that there is no official body that sets grade definitions for tonewoods, as there is for the general lumber industry. If one is not familiar with how a particular supplier grades, no objective information is conveyed by tonewood grading. Even the most reputable suppliers have to make subjective judgments about grading, and most of what distinguishes the higher grades are cosmetic differences, such as consistent color, that do not affect musical function. In the current market, one often sees wood called 5A, which is beyond anything on the old scale, that would not be given even an AAA grade by a conservative grader. On Ebay one gets the impression that 5A is where the grade scale begins. I have seen woods there that are of doubtful use at all for acoustic guitars described as 5A, or even 7A. I have seen guitar and wood dealers who ought to know better refer to a guitar's wood as being extremely high quality, when it was wild grain, flat sawn wood that I would not be willing to build with at all. New terms such as "exhibition grade," "reserve grade," and "museum grade" have appeared. There is no objective information conveyed by these terms. When I mention grades with regard to woods; I do so consistent with the older, conservative usage. In no case will I use wood that is not the best I can find in terms of tone, strength, and stability. But I am increasingly in agreement with a builder who told me, "There are really just two grades of wood: wood I would build with, and wood I wouldn't."

For information about the general characteristics of various tonewoods, I refer the reader to the article by Dana Bourgeois in my Resources section.

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Body size and style

I build in several sizes and body styles, as well as with different bracing patterns. Usually a guitar's size is given by the width of the lower bout, although that is only one dimension.

By this measure, I have built 13-1/2", 14-1/2", 15", 16", and 17" guitars and will custom build in any of these sizes. My designs are a little rounder in the lower bout and smaller in the waist than, for example, the body shapes of Martin guitars. In each size, the body depth may be varied. Another important design factor is the point at which the neck joins the body. I join necks at either the 12th or the 14th fret. When joining at the 12th fret, I often use an original shape for the upper bout with the sides recurving into the neck in the fashion of a member of the viol family. This resembles a shallow double cutaway and allows fret access similar to that of a 14 fret neck while providing a striking visual element and stiffening the guitar's sides. At the player's option, I will add a cutaway to the treble side of the body, either with or without the recurve on the bass side. Another option is an armrest bevel on the lower bout. These design factors affect both the sound and the playability of a guitar, and I will discuss them with you when you place your order. I will consider building shapes other than those I already use.

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Bracing I use two types of bracing systems. One is the X-brace originated by Martin and used by almost all steel-string guitar builders. My X-bracing varies somewhat from Martin's, in part because of the greater stiffness I give my tops across the grain with my arching system. I scallop the braces to differing degrees depending on the size of the instrument, the tonal wishes of the customer, and perhaps most importantly, the characteristics of the individual top. Final brace shaping is done by tap tuning. This is one area where a factory, using a one-shape-fits-all brace design, cannot compete with a hand builder.

My other bracing system is unique to my guitars. It is designed to take full advantage of the high lateral arch of the top, and is not easily described with a word or letter. For want of a descriptive name, I have come to call it Klepper bracing. It employs long, scalloped longitudinal braces, and cutout lateral braces in the style made famous among classical builders by Bouchet. The lateral braces are topped with carbon fiber/epoxy composite. I have used it enough times now to be confident of its strength and its sound. Although by no means lacking in bass, in comparison to X-bracing guitars with this system are more balanced toward the mid-range. They are loud and project strongly; one person described them as sounding as if the sound was originating out in front of the guitar. Because of this tonal balance, I prefer not to use this bracing system on small bodied guitars, which to be balanced are in need of a bracing pattern that will lean more to the bass. I have used it successfully on guitars 14-1/2" wide and larger. On a 16" body, which is naturally stronger in bass due to the size of its soundboard and air volume, Klepper bracing produces a sound that is strong, rich, and vibrant; its projection makes it ideal for performers. On all my guitars regardless of the bracing type, I strive for a sound that is clear and vibrant in all registers, with trebles that retain a strong fundamental all the way up the neck.

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Sides

The sides (also called 'ribs' or 'rims') of a guitar are crucial to its structure. They must provide a rigid platform for mounting the top and back. They absorb much of the compressive force of the strings.

Because of the stiffness they gain from their curvature, they radiate very little sound, and do so inefficiently. They do not transmit bass frequencies to the guitar back; it is physically impossible for a soundwave as long as that of the bass tones to be transmitted by material of this thickness. Bass is transmitted to the guitar's back by the air inside the box.

I build with very rigid sides. In most cases I use a double side--two layers of wood laminated together. The inner layer is usually mahogany, but in some cases will be walnut or East Indian rosewood. These double sides should not be confused with the plywood sides used on some factory guitars. The double side method is used, for example, on the guitars of the renowned classical maker Daniel Freiderich, and on the most expensive classical concert model made by Jose Ramirez. Once the sides are laminated, they will hold their shape without being clamped into a mold. They are far more resistant to cracking than a standard side. In addition, I use reverse kerfed liners (the blocks which build up the connection between the top or back and the sides), and laminate solid layers on top of those liners, which adds to rigidity and gives a clean interior appearance. Finally, I cross the sides with spruce braces for even more resistance to cracking if the guitar should strike something, and even more rigidity.

I often add a sound port to the side of the guitar in the upper bout on the bass side. These were pioneered by the classical guitar maker Robert Ruck. They serve multiple functions. First, and most noticeably, they radiate sound from inside the guitar in the direction of the player, allowing him or her to hear the instrument better. This can be helpful in a performance situation. It complements the double-side construction, which tends to make a guitar project its sound more forward. Next, they broaden the bass response of the instrument, by providing an additional port from which bass frequencies can radiate. A guitar body is a resonator, in some ways like a Helmholz resonator (think of blowing across the opening of a bottle). A smaller hole than the main soundhole, located more toward the end of the body, will create a lower-frequency resonance. Last, they add some midrange by venting air resonances that would otherwise cancel and be lost inside the box.

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Neck and tail blocks In guitar construction, there are solid blocks glued to the top, back, and sides at the upper and lower end of the body. The tailblock holds the sides together and provides a mount for an endpin or strap button. The neck block (or 'headblock') provides a mount for the neck. Most guitars have these blocks made from a single piece of wood (usually mahogany), with its grain running parallel to the sides. This is needed in order to present a good gluing surface to the top and back. If the grain ran across the sides, it would resist splitting but present an end grain surface, which does not glue well, to the top or back. It is common in guitar repair to find instruments that have split across their neck or tailblocks from a blow. Many of these injuries can be avoided by adding laminations to the blocks with grain running at cross directions. My tailblocks always have a cross-grain lamination. My neck blocks are more elaborate.

Guitars have been built with the grain of the neck block running in one of three different directions: parallel to the sides, parallel to the neck, and perpendicular to the sides. Each has its strengths and weaknesses. The most common on steel-string guitars, parallel to the sides, has the advantage of presenting a good gluing surface to the top and back, but the disadvantage of splitting easily from a trauma. Classical guitars have traditionally been built with the neck and neck block of a single piece. The block has a foot (called a Spanish foot) that extends along the back of the guitar and provides extra support for the neck. This works fine for single piece neck and block construction where the sides are let into channels in the block, but when the neck is built separately and joined to the body, as with virtually all steel-string guitars, it has the problem of presenting an end grain gluing surface to the sides. The last possibility is running the grain of the block perpendicular to the sides, i.e., vertically from the top to the back. This is done on violins and members of the violin family. It prevents splitting and gives a good gluing surface for the sides, but presents an end grain surface to the top and back (which is not a big problem for violins, since their tops and backs are intended to be easily removed).

So which way is best? Fortunately, this is not an either/or choice. I laminate a three-piece neck block of mahogany, using all three grain directions. A section running vertically from top to back glues to the sides, providing them with resistance to splitting. To that is glued a piece that runs parallel to the sides, to provide a good gluing surface for the top and back. Last, a Spanish style foot is glued into a dado in the base of the block, to add the support gained from extending the block along the back.

Another thing you will see inside my guitars is a pair of rods running from the upper portion of the neck block to mounts on the sides of the guitar just below its waist, and close to its back. These are double thickness carbon fiber/epoxy tubes that function as triangulating struts. They relieve stresses in the guitar's top and upper sides. The pull of the strings (about 180 pounds) puts a compression load on the end of the guitar body where the neck joins. A large part of this load is absorbed by the guitar top. The top is able to receive this force, since it is directed against the end grain of the top at its edge. But the price of this is stress that is transmitted through the entire top of the guitar, and inhibits its vibration. The sides of the guitar are distorted by stress, and the string pull also becomes torque--a rotational force--on the neck block. These forces gradually distort the upper bout of a guitar over a period of years, and cause a change in its neck angle. Eventually, the neck of the guitar will need to be reset. The carbon fiber/epoxy struts in my guitars transmit a major portion of the forces generated on the upper bout by string pull to the guitar's sides in the lower bout. The rods meet those sides at a very oblique angle, and thus transfer the force nearly on edge, which is the direction in which the sides are best able to absorb it without distorting. Stress in the sides of the lower bout does not inhibit vibration as stress in the top does, or lead to the upper bout distortion that requires a neck reset. The net result is relief of both the compression on the top, leaving it freer to vibrate, and the compression and torque forces on the sides and back. I don't want to say "never," but I expect my guitars to go many times longer without needing a neck reset than do guitars with standard construction. And I specifically guarantee them for life against needing this common and costly repair.

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Neck

Rigid, strong, and stable are the key words here. The neck must hold the 180 or so pounds of pull generated by a set of steel strings. It must resist warping or flexing, and do so over the lifetime of the guitar. When the neck vibrates in response to the strings, that is energy lost that will not be transmitted to the air by the top and back of the guitar. And the neck must not be overly heavy, or the guitar will not balance well.

I build with laminated necks. The laminations run lengthwise and are typical of many high-end jazz guitars. They are more stable than single piece necks, since any tendency of the wood to warp is countered by an opposing piece. They allow harder, stiffer woods to be used in the center of the neck, where they can provide the most rigidity at the least cost in extra weight. They are much more resistant to cracking from a trauma. They provide an opportunity to add decorative beauty. The only downside (for some) is that they are less traditional on flattop guitars than a single piece neck. I think that the benefits overwhelm that tentative downside.

I add to the interior of the neck an adjustable truss rod (which allows for compensation of any curvature induced by string pull) and on either side of that, a pair of carbon fiber/epoxy bars. This composite material has a stiffness to weight ratio higher than any wood; higher in fact than steel. Then I laminate layers onto both the face and rear of the headstock (or 'peghead'), which adds both strength and beauty. I usually do what is called "backstrapping"--laminating multiple layers of thin wood on the back of the headstock that run down into the neck and are shaped as part of the neck. Backstrapping has been traditional on high-end custom banjo necks. This gives great strength to a place that often breaks when a guitar is dropped--the junction of the neck and the headstock. The use of contrasting multiple woods makes for a beautiful and dramatic visual element as well.

I also often build with the fretboard of the guitar elevated from the guitar's top. This is standard practice on archtop jazz guitars, but has only recently been done on flattops. Classical guitar builder Thomas Humphrey was among the pioneers of this construction method. He noticed that harps have a longer sustain and stronger fundamental in their notes than do guitars, and conjectured that this is due to the strings pulling upward on the soundboard. On a guitar, the string pull is near parallel, but actually slightly downward of the top's surface. With the fretboard elevated, the string pull on a guitar is move up a few degrees, so there is a slight upward pull on the top. Many classical guitar builders now use elevated fretboards. In addition to its potential for enhancing sustain and fundamental response, it also makes the frets that are over the body easier for the player to reach--the guitar body does not block the players hand so much as when the fretboard sits on the guitar's top.

The elevated portion of the fretboard is supported by a piece called the neck extension, which is attached to the neck by a rabbeted lap joint. I extend the carbon fiber bars into the neck extension for increased strength and rigidity. The extension with these rods embedded in it is so rigid that it does not need to be glued to the guitar top for its full length; it can be all or partly clear of the top. This is called a cantilevered neck extension. The advantage of this is that it leaves the upper bout of the guitar free to vibrate, rather than restricting and damping it by gluing the fretboard to it all the way to its end, as in traditional flattop guitar construction. Another advantage is that a cantilevered neck extension, together with a hardware-joined neck allows for easy adjustment of the neck angle.

I began building guitars using traditional tapered dovetail neck joints. These are very difficult to make and adjust, but also very strong.

In recent years, many if not most builders have changed to using hardware joints: in plain terms, nuts and bolts (but very specialized ones). They are now used on some of the finest and costliest handmade instruments. These joints are just as strong as dovetails, and allow for a much simpler job and less costly job of resetting a neck should this repair be needed.

At first I resisted hardware joined necks for reasons of traditionalism. When I began in guitars in the 1970's, bolt-on necks were considered inferior, and I took pride in being able to make and adjust the complex dovetail joint. But now I use both styles of neck attachment, depending on the style of guitar and the wishes of the player.

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Source: http://www.klepperguitars.com/about.html

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