String

The string is defined by the material properties of a single strand and the number of strands it consists of. Its final length is calculated automatically based on the brace height specified in the Draw settings. The following three properties are required:

Strand density: The linear density of a single strand (mass per unit length). This determines the overall weight of the string, which is an important factor in a bow’s efficiency. Additional masses on the string — such as servings or nocking points — can be accounted for separately in the Masses settings.

Strand stiffness: The stiffness of a single strand (force per unit strain). This value determines how much the string stretches elastically under load.

Number of strands: The total number of strands in the string. The string is treated as an endless-loop string in which all strands run virtually parallel, allowing their properties to be added together. Strings with extreme amounts of twist might break this assumption.

Note

The linear density of a string material can be measured easily using an accurate scale (mass divided by length). The stiffness, however, is more difficult to obtain. Manufacturers generally do not publish this value. The table below lists the results of tensile tests for three common bowstring materials, done by the German Institutes for Textile and Fiber Research in July 2018.

Material	Linear density [kg/m]	Breaking strength [N]	Elongation at break [%]	Stiffness [N/100%]
Dacron B50	370e-6	180	8.5	2118
Fastflight Plus	176e-6	318	2.9	10966
BCY 452X	192e-6	309	2.5	12360

Table: Material properties for common string materials. The stiffness values are a linear estimation from breaking strength and elongation.