In mooring of vessels, wire ropes or fibre ropes are commonly used for tying the vessels to mooring system. It is not recommended to use them together in mooring. Why?

Mooring lines are provided by vessel while the shore provides the mooring points. Wire ropes provide a more rigid mooring system than fibre ropes. When a high degree elastically is required, fibre ropes would be a better choice. The mixed usage of wire ropes and fibre ropes is not recommended because of the uneven tensioning of ropes. Owing to different material properties associated with wire ropes and fibre ropes, it is almost impossible to allocate uniform tension on both types of wires. As a result, there is possible occurrence of overloading in some ropes.

This question is taken from book named – A Closer Look at Prevailing Civil Engineering Practice – What, Why and How by Vincent T. H. CHU.