Rust stains extending into the cross section of natural fibers and nylon fibers can lower the line strength by ______%?

• A. 10%
• B. 25%
• C. 60%
• D. 40%

Answer: (D)

Rust stains that reach into the fiber cross-section show that iron contamination and moisture have penetrated and damaged the interior of the rope. This isn’t just a surface stain; it means the internal structure is weakened, creating micro-cracks and reducing the effective area that can carry load. For natural fibers and nylon, this internal degradation typically lowers line strength by about 40 percent. Values much smaller would miss the depth of damage, while a much larger drop isn’t consistent with rust staining that extends only into the cross-section.