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Why Do 'Nylon' Fishing Lines Break? Distortion is the Truth

My story is familiar, and not new. There I was in the tinny (Kiwi speak for an aluminium dinghy) parked over a favourite patch of foul, weed covered ground.

The berley -(groundbait, chum, your call) trail was well under way, dispensing it's seductive odour down a gentle current. I had drifted down an unweighted pilchard, and felt one or two tentative touches. Time to check the bait.

Reeling in, I came up tight to the throbbing pull ... of kelp. When the blue haze of my swearing cleared the immediate area, I put down the rod. I wrapped a towel round my hand, took a couple of wraps of line, and started to pull.

I was amazed then, and am amazed still, at how much pressure it takes to break mono. Even the 8Kg. (16lb) line I was using put up a good fight. It was sufficient to pull the tinny around until the line parted with a resounding crack.

I re-rigged, and sent another pilchard down the berley trail. Soon, a light tap indicated I had caught the attention of a fish. That attention turned into full-blooded interest.

Line began to peel off the reel under the light restraint of my thumb. I put the reel in gear, started winding to remove the slack, and pulled up on the rod to set the hook. The fish's immediate reaction was predictable, but what followed was not so predictable.

The fish was good. Big, powerful, and knowledgeable about where safety lay, the fish took off on a direct course for the rocks and kelp. I don't know whether or not he made it, as he did not have to.

Halfway back to the safety of the rocks, the line parted. If the air was blue during the snagging episode, it was black and blue now.

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I checked the drag. Maybe, I had been silly, and not checked it before starting to fish. I had not, on this occasion at least, been silly. I checked the guides to make sure that a rough spot had not cut the line. All the guides were in good nick.

An inspection of the line near the break did not reveal any scuffing that would indicate the line had rubbed on the rocks.

Bemused and bewildered, I re-rigged and sent another pillie on it's way. Over the course of the next hour or so I had a pleasant time regularly catching, and mostly releasing, snapper that were little better than pan sized.

Getting close to the time I was going to pack it in for the day I felt the sudden weight of a big fish. It felt at least the equal of the big fish who had broken me off earlier in the day.

This episode was an encore of the first. The fish took off. I tightened up. The fish lunged for cover. Ping went the line.

The sea nearly parted at the ferocity of the naughty words that spilled from my foaming lips.

To Check for Line-Guide Problems

Grab a piece of cotton wool. Bend the rod so the guides are on the outside of the curve. Pull the cotton wool through the guides. If the cotton wool snags you have a problem. Replace the guide(s).

When I got home that night I re-checked the drag, guides, and line near the break. Nothing was amiss. I could not understand it. The line I was using was a long term favourite of mine. It had, up till now, performed very well. My faith in this line was now well shattered. Very soon afterward I changed the line on all my reels to another brand.

That was pretty much that, I thought.

It was not. Over the next few months I took more notice of what people were saying about mono. There were too many stories similar to mine to ignore.

Trouble was, my theory about my former favourite brand being the culprit for my misfortunes was in question. There were as many complaints about other brands as there were about mine. Even more puzzling, the complaints covered all brands, the cheap and the expensive.

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Time to dig a bit deeper than my one trip, bad result, knee jerk reaction.

As usual, the truth took some digging to find. It was well disguised amongst a morass of misinformation, myths, and legends.

Too many fishermen give too little attention to the mono they buy and use. Line joins each part of a fishing tackle system together. If you are into flow charts and systems engineering, you would call line the 'break point'. It is that part of the system on which all else depends.

Most of us know the basic rules for the care of mono.

Limit the time it spends in the sun. Never store mono, on your reel or otherwise in hot, sunny areas. UV is lethal to mono. Check regularly for nicks and scrapes. Even apparently innocuous scuffing has deep-seated bad implications for mono.

Basic stuff that requires very little time or effort, but information that did nothing to explain my broken line problem.

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The truth of what happened to my line is distorted.

All mono fishing lines are elastic. They stretch. Most stretch in the order of 5 to 12%. (I am using the term "mono" here generically. Many lines today are in fact copolymers, and even tri-polymers. That is, they are constructed of various combinations of polymers.)

When mono stretches, it's structure and shape changes. As it stretches, it becomes thinner and harder. Sometimes it's shape changes from cylindrical to oval.

Both these changes begin to change the molecular structure of the line. Sounds bad, but the fact is that mono has an extraordinary ability to return to it's original shape and structure. Breaking mono in good condition requires some effort.

First, all the stretch has to be removed from the line. Once this is achieved, the line begins to reach what the boffins call the 'non-recoverable distortion point', NRDP.

Once the line has reached the NRDP it is all over for the line. As the name of this point suggests, once the NRDP is reached the line cannot recover it's original shape or structure. It is flawed. Very little pressure is needed to break the line.

The problem for the fisherman is the lack of visible evidence of NRDP.

The NRPD does not occur throughout the length of the line. As the name of the condition suggests, it occurs at a point, or a series of points along the line. The situation that I outlined at the beginning of this article is a classic for producing non - recoverable distortion points at one or more points along the line.

If you are lucky, the NRPD only occurs at the point where the line breaks. (It is recommended practice to cut off at least a 1m piece of line above the break). It is difficult if not impossible to detect further NRPDs in the line.

Sometimes a section of line may appear 'milky', this is a sure sign of a NRPD. Cut this section out, well above, and sometimes below, the milky area.

For fastidious fishermen whose opportunities to achieve a fishing aim are few and far between, there is little alternative but to change the line after a break off. Big-game fishing and record seeking spring to mind.

Trout fishermen who break off a fish on the tippet section would be wise to change the tippet. I know more than a few good, and better, trout fishermen who routinely change the tippet section after each good fish - me as well.

Line is the critical component in a fishing tackle system. Too often we rush to blame the line for failing. Too often we ask too much of the line. Most often the truth of line failure lies in the way we treat line. But then none of us distort the truth about our role in losing fish, do we?

fish illustration by Bish

Article written by Tony Bishop

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