Rope Strength
How Do You Measure Rope Strength?
Each type of line, natural fibre, synthetic and wire
rope, have different breaking strengths and safe
working loads. Natural breaking strength of
manila line is the standard against which other
lines are compared. Synthetic lines have been
assigned “comparison factors” against which
they are compared to manila line. The basic
breaking strength factor for manila line is found
by multiplying the square of the circumference of
the line by 900 lbs.
(900 lbs. X circumference 2 =
breaking strength)
To calculate the breaking strength of synthetic
lines you need to add one more factor. As
mentioned above, a comparison factor has
been developed to compare the breaking
strength of synthetics over manila. Since
synthetics are stronger than manila an
additional multiplication step is added to the
formula above.
(Comparison factor X 900 lbs. X
circumference 2 = breaking strength)
Following is a comparison factor chart for
synthetic lines:
| Line Material | Comparison Factor (greater than manila) |
|---|---|
| Nylon | 2.5 |
| Dacron | 2.5 |
| Polypropylene | 1.4 |