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October 26, 2001

20-pound Line Test

We chose a common line size useful for many applications - 20-pound - and subjected 85 different lines to identical testing procedures.

Take a look at most any ad for fishing line or any line manufacturer's Web site. You'll see pretty much the same claims made over and over: Casts farther! Better knot strength! Smaller diameter! Strongest monofilament we've ever made! Superior abrasion resistance! Supersoft and limp! and, always, Quality! 

It's easy to get tangled up in so much rhetoric. But what does it all really mean? Where can an angler go to sort it all out? Nowhere, in fact. Quite simply, no industry standards exist to help consumers sort out the qualities of fishing lines; no laws require manufacturers to reveal any particular product information. Or, put another way, line manufacturers can pretty much make whatever claims they want. Then it becomes caveat emptor, baby - you pays your money and you takes your chances.

But without reliable line-testing machines, educated decision-making gets pretty dicey for the average fishing-line consumer. 

That's why we elected to undertake the most comprehensive line test ever. We chose a common line size useful for many applications - 20-pound - and subjected 85 different lines to identical testing procedures. We assessed the two parameters we could measure objectively: tensile (break) strength and abrasion strength/resistance, as well as measured the actual diameter of each line with calipers. We also tested for knot strength; the sidebar on page 74 explains why we decided not to publish those findings. In all, we performed nearly 1,200 separate tests over three long days of testing.

We didn't test limpness or softness: Although these qualities are important to anglers, they're hard to quantify. Moreover, unlike break or abrasion strength, limpness or softness is pretty easy to assess just by the line's feel.

THE TEST

Diameter

Although not really a test, measuring the diameter of each line was a critical part of the results because we rated strength as a function of line size, as discussed below. We checked the diameter of every line in three different areas with a Teklock manual caliper. While calipering monofilament (solid, round strands of nylon) is pretty straightforward, checking braided lines can be trickier since they aren't solid and tend to collapse (flatten) in the jaws of a caliper.

Tensile Strength

For a real-world test of monofilament lines' break strength, 73 different monos were soaked for at least two hours in fresh water at room temperature. (Monofilament loses a bit of strength when wet; that's why the International Game Fish Association similarly wet-tests monofilament line samples submitted with world-record catch applications.) Braided lines do not lose strength when wet; we tested those dry. We tested five samples of each line on a factory-calibrated MTS tensile tester, which provided a computer printout of the result. Abrasion Resistance

For abrasion resistance, we tested six samples each of 85 different lines, all in exactly the same way. We used a machine made just for testing abrasion resistance in lines - the same machine used in our abrasion test of 8-pound lines in July 1998. For each test, we attached a weight to the lower end of a piece of line approximately 12 inches long. Then a loop in the upper end of the line was placed onto the end of a metal arm that pulled the line up and down over a 150-grit steel cylinder at 132 cycles per minute. A counter tracked the number of cycles until the line broke. Between tests the cylinders were brushed to assure the coarse surface was free of line particles. All lines were tested dry. Slight differences may occur in wet versus dry lines, but relative wet-dry differences among lines should be minimal. It is worth noting that this test could be varied by using very heavy weights so that many fewer cycles on average would be needed to break lines or, conversely, by using very light weights so many more cycles would be needed. Since some lines may abrade differently, different approaches could change the results. We picked what we felt was a middle-of-the-road amount of weight. Also, keep in mind that in this test we measured one common form of abrasion - the sort that might simulate a line rubbing against a boat's hull or around a piling. Measuring abrasion against a sharp object to simulate a fish's teeth might produce different results.

 

ANALYSIS

For each line, we computed to the nearest tenth of a pound the mean (average) of five breaks. By also computing the standard deviation of these five averages, we could compare tensile uniformity in lines. That is, assessing how consistently each broke and then placing each within one of four general categories: excellent (best since minimal deviation shows great consistency; always desirable and one way to assess the quality that a manufacturer brags about), high, moderate or low (least desirable).The recognized standard for tensile strength in industry and science is break strength (stress) as a function of the object's size, that is, applied load divided by cross-sectional area. In testing fishing lines, this requires dividing the mean break strength of each line by the surface area of a cross section, which, being a circle, is simply pi (3.14) times the radius squared. Resulting numbers were very high from dividing by tiny areas (e.g., 0.000025 square inch), so to keep the numbers as manageable decimals and easy to compare, we divided each line's tensile strength by 10,000. The resulting figure we deemed our tensile-break-strength rating. We could have simply listed the average of five breaks. But strength must be considered relative to size. Put another way, if some models of 50-hp outboard engines weighed as much as 150 pounds and others as little 70 pounds, small-boat owners would want to know. Line manufacturers could more cheaply offer 20-pound mono with the diameter of what we'd expect in 80-pound. There would be more area to resist abrasion, but anglers generally benefit from smaller, thinner lines because these cast better than thicker lines, offer more line capacity on the reel and provide lures and baits with more action, thanks to less water resistance. To determine and compare abrasion strengths, we dropped the highest and lowest of the six tests on each line, then averaged the remaining four, producing a mean number of cycles to break. Again, we wanted to offer abrasion as a function of the line's overall size. That way, for example, a very thin line with more expensive, added polymers to resist abrasion might have the very same abrasion resistance as a much thicker line. Without knowing the thicknesses of these two lines, you might assume one line is as good as the other for abrasion. But most anglers would prefer the thinner line. To factor in line size, we divided each line's mean break (number of cycles on the abrasion tester) by the line's diameter, not its cross-sectional area. The abrasion test stressed only one part of the surface of the line, unlike a tensile test, which stresses the entire line simultaneously, so testing against cross-sectional area would have skewed results. This produced our abrasion-strength rating. Finally, we wanted to take into account both break and abrasion strength. To prevent the much higher numbers of the abrasion-strength index from skewing the overall rating too heavily, we multiplied the break-strength rating by two, then averaged that number with the abrasion-strength index to get the combined rating.