Birth of the Packaxe

by Francis Kosheleff

Previously published in Guild of American Luthiers Quarterly Volume 9 #2, 1981, updated 1994 and Lutherie Woods and Steel String Guitars, 1998

The Need. Several years ago after reading an article in Guitar Player about the hassles of traveling with a guitar and remembering my own camping trips in Europe and the United States, it dawned on me that the answer was a folding guitar. That night I went to work on that idea with pencil and paper, slept over it, dreamt about it, and the next morning started work in the shop. The following Saturday I went to the flea market and bought several cheap, broken acoustic guitars to experiment with. Later on that month I started the actual construction of the first folding guitar and named it the Packaxe. The name Packaxe is now trademarked.

The idea of a hinged neck on a guitar is not new. It must have occurred to many luthiers before me, yet I had never seen a folding guitar, nor read or heard of one. Knowledgeable people usually told me that such an instrument could not possibly work for a hundred reasons. I went ahead anyway building several types of guitars with folding necks, and sure enough, there were problems, lots of them. But for an inventor, this is a challenge to be enjoyed.

When I decided to patent these new guitars, the first step was a search at the patent library in Sunnyvale. This was an experience! I spent days pouring over books and files going back almost to the turn of the century and found a number of patents for folding guitars. Now I know why the folding guitar never became a hit. Some of these inventions were quite clumsy and acoustically unsound. I suspect the inventor did not realize that the purpose of a guitar is to play music. A couple were on the right track but stopped short of a workable solution, probably because they did not actually build one. If they had, they would have found out all the things that can go wrong in the process.

Photo by Francis Kosheleff.

Design Problems and Solutions. The first thing to cause trouble is the tendency of the strings to spill out in all directions when you fold the neck, and refuse to go back to their proper place when unfolding it. The remedy is simple. Use a higher nut with holes instead of grooves and a zero fret in front of it.

The second problem is that no commercially available hinge is perfectly suited for the job. Some can be modified or adapted (see Hinges below).

The third drawback is the inherent instability of a folding instrument due to the abrupt changes of tension when folding and unfolding. This will cause changes in the action and the intonation of the instrument that can be cured by designing an adjustable-locking device for the neck. On the other hand, an adjustable truss rod is not recommended because it would require adjusting every time. I favor building a laminated neck of maple and mahogany or other stable hardwoods, with graphite epoxy laminations or metal reinforcing for steel string guitars. The body of the instrument has to be sturdy and the gluing surfaces increased slightly to withstand the sudden jump from zero tension to full tension.

The fourth problem is that nobody believes such an instrument can work. The only solution is to let the unbelievers play the Packaxe. One problem, I was told, would be the quality of sound. In a normal guitar the neck is rigidly attached and plays a very definite part in the acoustic quality of the instrument. It was felt that this could be lost with a hinged neck. I too was afraid it would be a problem. Then I built my first good Packaxe and discovered there is no such problem. With a proper hinge, lock, and adjustment screws, and under the tension of the strings (even nylon strings), the neck is as rigid and secure as with any normal guitar and plays its proper part in the acoustic scheme.

Another would-be problem (that is not) is the need for a string tensioning device. The idea was that in order to fold and unfold the neck you need to slacken the strings. Since to do it individually with the tuning machines would take forever, you had to invent a device that would accomplish this quickly on all the strings at once. Indeed, there are several patents for such devices. From the beginning I was not convinced of the need for it, and my very first experiment with a flea market guitar dealt with this problem. I found that even with the heaviest steel strings, I was able to unfold the neck with little effort and without damaging the guitar.

All types of guitars can be designed with a folding neck, although some are more practical than others. For each type, the choice of locking device, hinge, shape, size, and material will depend on the intended use. For example, I have built several classical guitars that sound and look like any other classical guitars except for the hinged neck. They are designed to be used in the normal fashion with the option of folding for an occasional trip. At the other extreme I have a model that is designed for rough use (camping, backpacking, constant travel) which fits under the seat of any airplane. It is tough, it can be folded and unfolded in a second, and it needs only the protection of a cloth bag.

Hinges. Regular plate hinges or cabinet hinges can be used. However, the loose pin type should be avoided since the pin can drop out when the neck is folded. When the hinge is in the middle of the fretboard, it is located between two frets. It must be recessed below the surface so as not to interfere with the strings, but this will prevent the neck from folding all the way to the soundboard. It must, therefore, be altered to allow it to slide out of its recessed position. I file the three screw holes on one side of the hinge so they become long slits running perpendicular to the hinge pin. This will allow it to slide in and out. When the hinge is at the end of the fingerboard it is not necessary to alter it, since it can be mounted flush with the board on one side and higher than the soundboard on the other. It will thus allow a full 180° swing of the neck. With a flat fingerboard the crown of the hinge can even be used as an extra fret.

One other hinge I use is the so-called invisible hinge. It is designed to be mounted below the surface and still allow a full 180° swing. It is difficult to mount on a guitar neck because it must be recessed into the end of the neck just below the frets with no room to spare on either side. The process allows for no mistake in drilling and cutting. This type has no resistance to the twisting of the neck that can occur in playing, and therefore the locking system must be absolutely secure.

Because of the need for adjustment of the action, no commercially available locking device is usable without alteration. I have designed at least a dozen practical systems for locking the neck in position. I make them in my shop since they require only a few metalworking tools.

I have used this simple adjustable locking device on several types of Packaxes. It is quick and easy to operate. Neck angle/playing action adjustments are made by running the machine screw, to which the latch connects, slightly in or out. The smaller screw, which acts as a neck-movement stop, is adjusted to coordinate with the neck angle setting.

This hingeless detachable-neck system utilizes a threaded insert which is epoxied into the neck. The profile of the neck-to-body joint makes the use of a hinge unnecessary.

Variations. On several models of Packaxes where a low profile is desirable when folded, the heel can be drastically shortened and the peghead built in a straight line with the neck. With the tuning machines reversed, facing the front, another inch or two can be saved.

Another type of Packaxe is one with a completely detachable neck. Usually one or two screws and a detachable tail piece is all it takes. When broken down, the neck comes off with the strings and tail piece. The strings are then carefully wrapped around the neck with the tail piece still attached. A few rubber bands is all that’s needed to keep the whole thing together. One advantage of this system is that one can have more than one neck for the instrument, with different scales or different strings, fretted and unfretted, and so on.

Lately I have been building large instruments, bass mandolins (mandobasses) and bass and contrabass balalaikas, most with detachable necks. For these instruments, the tail piece is designed like a draw latch to fasten or detach it by pulling one lever.