Stretch is the degree of a material to which it is able to be lengthened by pulling.

Stretch is one critical factor to be considered when designing a rig. Low stretch under high loads and other factors are important in the final performance of a rigging configuration.

Stretch can be of two types:

1. Structural
Of a permanent character. Caused when the initial load is applied.

2. Elastic (ES)
Given by the applied load (kN), wire length (m), modulus of elasticity of wireand it’s cross sectional area ( diameter2 x Pi/4 )
It is possible to calculate this value from the formula:

ES = Applied load (kN) x wire length (m)
Modulus of elasticity x Cross sectional area

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