What can be added to an eye splice to strengthen it?

Adding a thimble to an eye splice can significantly enhance its strength and effectiveness. A thimble is a small, usually metal or plastic device that is used to provide a smooth, reinforced shape for the eye of a rope. When incorporated into an eye splice, the thimble maintains the eye's shape and helps distribute the load across the fibers of the rope, reducing wear and preventing the rope from flattening under stress.

This use of a thimble is particularly important in applications where the rope is subjected to bending, as it protects the integrity of the splice and the rope itself. By minimizing wear at the point of tension, the thimble extends the lifespan and reliability of the rigging system. In contrast, the other options, such as a grunt knot or a bowline, do not offer the same kind of load distribution or protection and might not strengthen the splice at all. The slip knot is more prone to slipping under load, making it unsuitable for enhancing a splice's strength. Thus, utilizing a thimble in an eye splice is the most effective method for increasing its strength and performance in rigging applications.