Friday, May 1, 2009

Development of the carbon fiber twin tube guitar neck part 1

The guitar neck is long and thin, and subjected to more stress than any other component of the guitar. Each string has a tension between 20 – 40 lbs, and this force wants to bow or bend the neck.

In addition, each string is under a different tension, so this tends to twist the neck. Furthermore, wood absorbs moisture, and will change its dimension based on environmental conditions. Wood continuously expands and contracts because of this and changes the tune of the guitar.

Carbon fiber is not affected by environmental conditions. It will not expand or contract due to heat and cold. This is why NASA uses carbon fiber structures for the space shuttle and satellites, which cannot change when heated up to 248 F when exposed to the sun, or cooled to – 256 F when exposed to the darkness of deep space. So, no matter if you are playing under the hot lights in the desert, or in an igloo at the North Pole, or leave your guitar in the trunk of your car, your FiberSonixx neck will stay in tune.

Humidity has an even greater effect on wood. Wood can absorb a great deal of moisture. In fact, it will not stop until the moisture content equals that of its environment. Wood can range from “dry as a bone” to “waterlogged.” As wood gains moisture, it expands. This is why every guitar factory in the world dedicates a large area to conditioning the wood prior to manufacturing. The wood is maintained in this ideal environment until the product is shipped. What happens after that is anyone’s guess. Engineers in the timber industry have measured the Coefficient of Moisture Expansion of various types of woods. For example, for a maple neck, a difference in moisture of 10% can change the length of the neck by 1/16 of an inch! Ask any musician who has gone on stage under the hot lights. The lights dry out the wood and cause the neck to shrink, requiring a retune.

Before beginning the design phase we looked at various option with carbon fiber. Should we combine carbon fiber with wood and try to get the best of both worlds? Should the neck be solid or hollow? What process should be used to make this part? With carbon fiber composites, there are many options to consider, and each has it pros and cons. We wanted a neck that was stiff enough, but not too stiff. The neck could not twist. Tone is critical, so we considered that into the design. The solution we came up with is called TwinTube. The FiberSonixx TwinTube neck is designed with a double tube construction. We have molded carbon composite tubes side by side into the shape of the neck which creates a unique structure that has several benefits.

-The double tubes are connected on one end to form a long continuous U Tube. This increases the wavelength of the sound waves traveling down the neck, resulting in a warmer, richer tone.

-The center wall formed between the two tubes adds strength to the structure like an “I” beam. This maintains the cross sectional shape of the neck. In addition, the center wall supports the pressure exerted by the truss rod.

-The double tube construction improves the torsional stiffness of the neck to reduce twisting to maintain consistent string relief.
-The tubes can be hollow or filled with foam to custom tune the tonal response of the neck
-An aluminum Heel Lock is molded into the neck heel area to provide a secure and reliable mounting means to the instrument body. The Heel Lock improves the sustain of the string vibration because there is less energy loss at this juncture.

-Aluminum sleeves are located in the headstock to provide support for the tuning gear mechanisms.

Put all these features together and what do you have? Something different! The TT construction allows us to design very high stiffness in the neck so that no truss rod is needed. Or, we can make the neck as flexible as a wood neck. What is cool about it is that it is consistent and stable neck after neck. This baby simply does not warp.

Now that we have a stiff and stable neck, why not slim it down so it is easy to play? The performance of the guitar is in the neck. A thinner neck allows the musician to play faster. Hey, what about a friction free coating? Did someone say superfast?

This is just the start. We have a ways to go. In future blogs I will go into the headstock design and the fingerboard.

Thursday, April 30, 2009

Introduction to carbon fiber composites

Fibersonixx is a supplier of carbon fiber parts to the guitar industry. We produce parts out of carbon fiber reinforced epoxy that replace and out perform traditional wood products.

First a brief primer on composites. A composite material is comprised of 2 or more materials. In the old days, it was straw reinforced mud that was used to build houses. Another example is rebar embedded in concrete. Now there are very light weight fibers used to create high performance structures. The optimum fiber is carbon fiber because of its extreme light weight, high stiffness, high strength, and relative affordability.

Carbon fiber comes in spools that are processed in a textile type operation to combine the fibers with expoxy resin to create what is known as prepreg. This material is placed into molds and compressed to form the desired shape.

The high stiffness to weight ration of carbon fiber reinforced composites makes it attractive for many types of structures ranging from aerospace to sporting goods. The types of products that can be produced are unlimited. Wild and cool shapes can be molded that would be impossible with wood. Check out some of the examples posted in this blog. We will be updating in future blogs so please check back often.

Zonda Carbon Fiber Supercar

Weds Sport Racing Wheel

Fibersonixx Carbon Fiber Electric Guitar Body

Another cool feature of carbon fiber is that it is impervious to temperature and enviromental conditions. This is why satellite structures are made with carbon fiber because they will not change dimension when exposed or blocked to the sun. This means a carbon fiber guitar will not change in dimension whether it is in a snow bank or in an oven.

Carbon fiber also has great tonal properties. Sound travels as a function of weight and stiffness. For example, a light and stiff structure will have a high frequency resonant ring to it. The fiber angles can be modified to reduce the stiffness and therefore the resonant frequency. What this means is that the structure can be tuned to generate the tonal response desired.

We will continue with more updates on the guitar development, so keep checking back.