Background
How a Limb Works
Design Considerations for Archery Bow Limbs
Article: Ahead of its Time for More Than 50 Years

Archery has been the mainstay of Gordon Composites for more than 50 years. Our composite laminates were first used in the Gordon Royal Bows, and then made available to the entire archery industry. Today, traditional, compound and crossbow bow makers at every level use Gordon glass to enhance the performance and beauty of their bows. Gordon glass is truly the choice of the best bow makers in the world.

Gordon Composites traces its roots to the early 1950s when the brothers George, Don and Dave Gordon Sr. pooled their resources to start a business using George’s chemistry background.

They started tinkering with resins and fiber reinforcements to produce products such as diving boards for southern California pools, corrugated lighting panels for commercial buildings and a fiberglass auto body for an all-electric car.

In 1952 they decided to experiment with producing their own line of archery bows using a fiber-reinforced laminate that George developed in his lab. The rest is history.

During the remainder of the 1950s through 1963, the Gordon brothers produced bows under the name brand “Gordon Royal Bows.” Some of the models they produced were the “King,” “Queen” and “Knight.” During this period they also developed and produced composite arrow shafts that were sold under the name “Graphlex” and “Glashaft,” which were very popular across the country.

Because they were producing bows and also selling Bo-Tuff laminate to most of the other bow manufacturers, there seemed to be a conflict of interest with some of their archery customers. In the early 60s, the brothers decided to sell the bow-making business to Browning Mfg. They then concentrated solely on producing high quality laminate for all bow manufacturers.

Root Archery, Bear Archery, Wing Archery and Ben Pearson Archery were just a few of their archery accounts during the late 60s and early 70s. Gordon Composites also furnished limb material for some of the first compound bows that Tom Jennings produced.

In the early 70s, a new continuous production system was put into operation. Shortly thereafter the company developed a process to produce bar stock (solid bow limb material). The company continued to supply the lion’s share of laminate and bar stock to the archery industry.

During the past five years, Gordon Composites has doubled production of archery bow limb material and in 2007 supplied products for approximately 650,000 compound bows, x-bows and target- or traditional-type hunting equipment.

For additional information contact Don Forrest at, (970) 240-4460, ext. 206, or donf@gordoncomposites.com.

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It is well known that the purpose of the bow limb is to store and release energy. Bows function by converting elastic potential energy stored in the limbs into kinetic energy and movement of an arrow. Energy stored in the limbs of the bow as they are deflected is transformed into rapid motion when the string is released, transferring the motion to the arrow.

One of the performance attributes of composites is often called “memory,” which refers to the material’s ability to return to its original shape when a stress is removed. Fishing rods, vaulting poles and golf clubs take advantage of this capability.

There are two categories of materials in composites: matrix and reinforcement. The matrix material surrounds and supports the reinforcements by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the matrix properties. The wide variety of matrix and strengthening materials allows the designer or engineer to choose an optimum combination.

The physical properties of composite materials are typically anisotropic, meaning they respond differently depending on the direction and location of any applied force. For instance, the stiffness of a composite panel depends on the design of the panel – the fiber reinforcement and matrix, the method of panel build, and orientation of fiber to the primary force. In contrast, isotropic materials (for example, aluminium or steel), typically have the same stiffness regardless of the directional orientation of the applied forces.

Getting to the point, stress is applied to a bow limb when the string is drawn. One side of the composite is actually stretched while the other is compressed. The fibers resist these two forces and the matrix spreads the load throughout the limb. When the stress is released, the “elastic” composite quickly “springs” back to its original shape. This action converts the elastic energy into kinetic energy and sends the arrow on its way.

We have no idea how the ancient nomads decided to add bone and sinew to their wooden bows but they obviously had a practical understanding of the process just described. Today we have computers and software to help us plot the stress-strain curve for a given material or composite. These programs actually color code the internal forces, enabling us to see how much and where stress is occurring. If we can see it and understand it, we can develop ways to make the limbs even better.

So where do we go from here? Is there a next-generation combination of materials lurking out there that will make bows better, stronger, longer-lasting or more affordable? If the progress in material science in the next 20 years is anything like the last 20, the answer is a resounding “Yes!” Change and progress will continue to be made in the foreseeable future and the evolution in laminates will continue for the benefit of materials users everywhere.

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When designing archery limbs with Gordon Composites materials there are some basic guidelines to follow to ensure successful limb performance and durability:

1. As a starting point, develop a design based on minimum material strength properties. Gordon material strength minimums are based on a 3 sigma standard deviation referenced to the data average.
   
2. Once a proper strength minimum is set, safety factors should be determined for fatigue life, axle shear, mounting shear, limb twist, limb deflection, brace height and limb length.
   
3. It is always important to strive for a constant stress design along the length of the limb.
   
4. In general, average stiffness properties are typically used to determine the nominal stiffness of the limb, realizing that the stiffness will vary within a batch of material (normally 3 sigma) and average stiffness will vary from batch to batch.

After deciding what the key performance elements of a targeted limb design are — e.g. high fatigue resistance or high speed — it is imperative to stay within design guidelines.

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The following excerpt is reprinted with permission from Inside Archery magazine. The article appeared in the September 2007 issue.

Like it or not, we are equipment oriented, and spurts in archery participation and industry growth have typically been linked to product innovation. Beginning in the 1950s, it was the development of reliable recurve bows that sparked expansion. In the 1960s, arrow shafts improved dramatically, and in the 1970s it was the amazing advent of the compound bow and the treestand that ballooned archery involvement.

While more recent innovations may not have been quite as monumental, they have been more frequent. Hunting releases, 3D targets, fiber-optic sights, expandable broadheads, carbon arrows, drop-away and total-containment arrow rests, laser rangefinders, scent-containment clothing, portable ground blinds, scouting cameras and much more have all made archery participation more attractive and enjoyable.

Through it all, thought, how performance has remained a central theme. As bows became more dependable, more enjoyable to shoot and more accurate, the sport and the industry prospered.

Evolving bow performance has hinged on a variety of factors, including refinements in risers, eccentric systems, bowstrings and cables. But in no area have the improvements been more enabling of archery progress than in the evolution of bow limbs. After all, it is the bow’s limbs that allow everything else to happen. If the limbs aren’t up to the task, no new high-performance cam, riser or cable system will carry the day.

From the very beginning of the modern archery industry in the late 1940s, limb development has been central to bow improvement. And surprisingly, a single longstanding company has been at the forefront of bow-limb innovation over the past five decades. That company, now called Gordon Composites, has been and continues to be one of the most influential companies in the industry.

To read the complete text, download the article by clicking here.

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