How Strong Are Nylon Fishing Line?

Written by james young
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How Strong Are Nylon Fishing Line?

Pound test ratings of the monofilament nylon fishing lines most anglers use today are only a rough indicator of the breaking strength. The manufacturing tests guarantee that the lines meet a standard, holding up to the rated weight for a reasonable period of time. Tie a crude knot in the line or bind it against a sharp rock and the apparent strength instantly decreases.

Pounds Test

The standard for monofilament line ratings measures the breaking strength of clamped line rather than knotted line. Static loads, not dynamic loads, are the basis of this measurement. Suspending a 10-pound weight from the clamped line successfully means the line passes the standard for a 10-pound test line. Low quality lines could vary enough in actual diameter that sections of line pass this test while other sections on the same spool would not.


Any knot tied in a fishing line reduces its strength. Special knots for working with monofilament use extra turns and line doubling to take away some of the stress and avoid the tightest bends. The coiled design of the good knots also absorbs some of the shock of a hard strike. A poor choice of knots reduces the strength of nylon fishing line by as much as 50 per cent.


Lines built for tough fishing conditions keep their original strength longer. Any scarring of the line whether from the jaws of a fish or from being pulled against rough objects will reduce the line strength. Cheapest grades of monofilament suffer the most damage.


Don't be tempted by bargain fishing line from a store's previous season's stock. Monofilament degrades and decreases in strength even just sitting on a store shelf. Ambient light and temperature during storage both affect line quality--line stored at home could be even more at risk. Old line is not just weaker--line past its prime can be permanently curled. Buy new line every year.


Ten-pound test lines from different manufacturers may show entirely different breaking characteristics. One brand of line of 0.25-inch diameter rated at ten pounds test could break at 5.22 Kilogram of strain. Another brand rated the same ten pounds test could have an actual diameter of 0.30 inches and an average breaking point of 6.35 Kilogram. Line of the best quality might withstand more than twice the rated load, breaking at more than 9.07 Kilogram of strain.

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