Bow String - String Materials

String Materials

Traditional materials include linen, hemp, other vegetable fibers, sinew, silk, and rawhide. Almost any fiber may be used in emergency. Natural fibers would be very unusual on a modern recurve bow or compound bow, but are still effective and still used on traditional wooden or composite bows. Sinew and hide strings may be seriously affected by water.

Widely-used modern materials are stronger for their weight than any natural material, and most are unaffected by water. They include:

Dacron B50 - (strength per strand = 22.5 kg., stretch = 2.6%), a polyester material. Because of its durability and stretch, Dacron is commonly used on beginners' equipment, wooden bows, and older bows. The relatively high stretch causes less shock to the bow, which is an important consideration for wooden-handled recurves. Dacron strings are easy to maintain and can last several years.

Kevlar 7-11 - (strength per strand = 31.8 kg., stretch = 0.8%), also known as Aramid, is a liquid crystal polymer material with a higher density and smaller diameter than Dacron, which results in a faster arrow speed (approximately 2 metres per second faster). There are two problems with this material. First, its limited stretch causes increased stress in the bow limbs. Secondly, a Kevlar bowstring may only last 1000 shots before breaking as it tends to fatigue due to bending at the nocking point. Failure tends to be sudden rather than gradual.

Fastflight - (strength per strand = 45.5 kg., stretch = 1.0%), introduced in the 1990s, is a high modulus polyethylene material, also known as Spectra, which results in a "plastic" look and feel. It is very slippery, so the servings have to be wrapped very tightly to prevent sliding. Special serving material has been developed to help overcome this problem. Fastflight has largely displaced liquid crystal polymers like Kevlar for bowstrings as it is more durable and fails more gradually.

In 2006, all US-based Spectra production facilities were requisitioned by the US Government, since Spectra is also used in body armor. Production of Spectra-based Fastflight has thus ceased, but the manufacturer (Brownell) has launched several alternatives, such as the Dyneema-based Fastflight Plus.

Fastflight S4 - (strength per strand = 73 kg., stretch = less than 1.0%) is made from a composite of 50% Fastflight and 50% Vectran making the strands thicker. Therefore approximately half the number of strands are required as for a Fastflight string. Vectran is a liquid crystal polymer similar to Kevlar. Mixing it with Fastflight avoids many of the durability problems associated with liquid crystal polymers.

Dyneema is a high modulus polyethylene material. It has very similar characteristics to Fastflight, though with a little more stretch. For this reason, many recurve shooters prefer Dyneema and find it more "forgiving" than Fastflight.