Synthetic Rope, Wire Rope, Knots, and Splices
Core concepts
Rope is a system, not a single item. Candidates must distinguish wire rope construction (strand, lay, core - fiber core vs. IWRC), the difference between regular lay and lang lay, and the meaning of lay length. For synthetic rope: nylon (stretch, energy absorption), polyester (low stretch, good UV), and high-modulus (Dyneema/aramid - high strength, low stretch, poor heat resistance). Knots and splices: a knot reduces rope strength substantially (often 50% or more), while a proper splice retains much more (commonly 90%+ for some splices, but verify per manufacturer).
Traps in questions
- Assuming a knot retains full strength - it does not; knots are for non-critical or tag lines.
- Confusing wire rope lay direction with rotation tendency under load.
- Ignoring broken wires, bird-caging, kinking, or crushing as removal criteria.
- Using synthetic rope near heat or sharp edges without protection.
Rule of thumb
For critical lifts, use splices, not knots. Protect synthetic rope from abrasion and heat; inspect wire rope for broken wires per the applicable removal criteria (e.g., broken-wire counts over a lay length).
Worked example
A tag line needs a quick attachment: a bowline is acceptable because the tag line carries no load. But a 1-inch nylon line used to hold a load must be spliced - a knot could cut capacity by half, turning a 20,000 lb line into a 10,000 lb line.