Bowstring A bow string joins the two ends of the bow stave and launches the arrow . Desirable properties include light weight , strength , resistance to abrasion , and resistance to water . Mass has most effect at the center of the string ; one gram of extra mass in the middle of the string slows the arrow about as much as 3 . 5 grams at the ends . String forms . Most bow strings may be described as either simple , reverse - twisted , or looped . Simple strings may be made of any fiber , twisted into a single cord . Such strings have been used in many parts of the world and are still effective and fairly quick to make . However , they tend to be weaker for their weight , and they may also come apart if not kept constantly under tension . They are normally secured to the bow by a knot at each end . Reverse - twisted strings are traditional in Europe and North America for most natural materials . Linen and hemp fiber have been widely used . The form is also used for modern materials . A reverse - twisted string is made of separate bundles , each bundle individually twisted in one direction ; the entire group of bundles is then twisted in the other direction . The result tends to be stronger for its weight than a simple or looped string , and holds together better than a simple string . Unlike some looped strings , the full thickness of the string passes around the nock s on the ends of the bow , where wear is usually greatest . Additional threads may also be laid in at the nocking points for the bow stave and for the arrow , which are sites of likely wear . The string may be secured to the bow by a knot at each end , usually a timber hitch , also known as the bowyer ' s knot . The traditional " Flemish " string has a laid - in loop at one end , which is easier than most knots to fit over the nock of the bow when stringing and unstringing . It is more trouble to make ; the short length , towards one end , that will form the loop is reverse - twisted first . The ends of each bundle are then laid into the main length of the bundles , which are reverse - twisted in turn . The Japanese bow string is made by reverse - twisting in different directions in the core and outer layers of the string . See Kyūdō . Looped strings are made of one or more continuous loops of material . Modern strings are often made as a single continuous loop : this is then served to give the final form . Disadvantages include the lesser amount of fiber at the ends , where wear is most likely ; this may be overcome by serving the string . In many parts of Asia , traditional strings have a single loop in the center , with the ends made of separate lengths tied on using a special knot . This design allows extra fiber to be used at the ends , where weight is less important and wear more likely . 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 bow s . 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 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 . Serving . Serving a bow string refers to the use of an additional thread , commonly wrapped round the main string at the nocking points where abrasion is most likely , and also used on looped strings to keep the two sides of the loop together .