Cinching Blood Knots  About Breaking Strain  Knot Thoughts   Nylon UV Susceptibility  Breaking Strain vs Shock Load  Line Stretch

 Most of the data and information on the web is US in origin and generally for much heavier, 10lb and upwards lines and big swivels and hooks. I've done numerous tests with lines of 6lb max and hooklengths down to 2lb. What has become clear is that much of the so called facts regarding line and knots is specific to the authors experience and tackle. As is mine except that I'll try to keep reminding readers that any facts only apply to whatever lines and hardware are being used for the tests. Other similar lines and hardware may give similar results but may not. The only way to 100% certain is to do your own tests.

I have no connection or affiliation with any of the companies or products mentioned in the following text.

 Cinching tucked half blood knots.

Note that the lines used are all nylon monofilaments. Fluorocarbons require a different approach and will be tested as time permits. Data and methods are very specific to the lines tested.

Something that's almost become written in stone is the cinching of tucked half blood knots. Somebody at some point claimed cinching the tucked half blood slowly kept the heat being generated to a minimum and prevented knot damage. Well I'm not saying that's never the case but for the lines I've tested it certainly isn't guaranteed.

When I cinch a tucked half blood I've always done it quite quickly or what might be described as very positive. Not a snatch but definitely not slowly. Two reasons 1) Some lines (mainly hooklengths) won't cinch a tucked half blood if you do it slowly, the knot will just unravel. 2) It simply doesn't feel right.

The slow method is forever being recommended on the internet but without any hard evidence to back up the claims so to that end I decided to do some tests with the sort of lines I use, main lines in this case, I'll do some hooklengths as time permits.

The test consisted of 28 tests in total for each of the four lines tested. An 8" piece of line was tied to identical 30lb Partridge micro swivels at each end with tension being applied until the assembly broke. A note taken of which knot broke and the data tabulated. As I wasn't expecting a great deal of difference I swapped the swivels over after 14 tests just in case there was some minor difference in the swivels. Tucked half blood knots will generally (if the line doesn't break first) break on the swivel. As such any tiny flaw could skew the results. Diameters are actual measured diameters and tests were done with line that had been soaked in water with a little washing up liquid for three hours. Here's what I found:

It's clear to me that for the lines and swivels used cinching the tucked half blood knot the way I do it, quick and positive is more likely to result in a stronger knot. In fairness, there isn't a great deal in it with the exception of the 6lb Float Fish which interestingly is slightly bigger in diameter than the others. Whether that's the reason or not I don't know. I'll try and get hold of some 5lb and add it to the tests as time permits.

EDIT: Got hold of some 4.4lb FloatFish but due to the line snapping more often than not before either knot gave way I gave up.

 About the Breaking Strain of Fishing Lines

As most seasoned anglers will be aware the breaking strain as written on the packet of fishing line is somewhat unreliable but few seem to be aware of why it is so. It isn't IMO manufacturers telling lies or trying to flatter their products but a lack of suitable standards by which to test. Why does it make a difference? you might ask, it breaks under a certain load or it doesn't, seems simple to me. It isn't that simple and I'll explain why.

The shorter the sample you test the higher the average breaking strain. Sounds ludicrous but it's a fact. All extruded filaments are subject to slight flaws and variations in diameter. A filament will break at it's weakest point so what you see on a packet of line is I suspect(1) an average of maybe 20 or so samples of whatever length the manufacturer decides to test. A simple example is probably the best way to illustrate why the sample length makes a difference:

A line machine manufacturer tell his customer that on average there will be a flaw in each metre of 10lb line that will reduce the breaking strain by 10%.

Line manufacturer A decides to take 10 1M samples and calculates the average - 10 samples measuring 9lb gives him average of 9lb so he labels his line as 9lb line.

Line manufacturer B using the same machine decides to take 10*10cm samples, only one of which will have a flaw as the combined length will be 1M. That's 9 samples at 10lb and one at 9lb. 99lb/10 = 9.9lb so his labels have 9.9lb on them.

This isn't meant to be a real world example. It's somewhat difficult to find test standards without paying for them and I'm not about to do that. Of the ones I have seen there's a European standard that specifies 20mm as the test length and an American one that specifies a 10" sample although the American one is from anchor point to anchor point having gone round a mandrel at each end. The real point to point length of the American standard is probably between 3 and 4". Neither standard IMO being really appropriate for testing fishing line. I can only guess at why there isn't a suitable global or at least continental standard but would suggest that it's down to the limited use of single fibre filaments. I can only think of three uses off hand - strimmers, guitar strings and fishing line. For the most part filaments are either woven, spun or some other use whereby filaments are in multiples where short length averages are quite sufficient.

Breaking strain is also dependent on moisture content and temperature. Nylon is hygroscopic and once fully saturated you can lose as much as 10% breaking strain from the dry value. Temperature also has an effect although less than moisture content. As best as I can ascertain around 1% per degree C. If you're using fluorocarbon hooklengths which aren't affected by moisture and seem to be less affected by temperature it's worth factoring in when choosing a mainline.

(1)Judging from the variation of printed breaking strains, some manufacturers may be specifying a minimum, maximum or average. As the test conditions are never stated it's difficult to tell.

 Knot Thoughts

On the face of it the idea that a 100% knot is unachievable would seem perfectly reasonable. In practice however it isn't always the case. Line can vary along its length by +-5% and more. If you were able to tie even a 91% knot in a section of line that was in the +5% then the line would more than likely break at a -5% point. It depends somewhat on the cause of the variation. Whether it's down to variation in thickness or microscopic flaws but in practice it does happen. Some lines and line to knot break ratio.

Just because the knot fails before the line doesn't necessarily indicate poor knot strength. It could just mean that the line diameter is more consistent, inconsistencies in diameter are further apart than the test length or the line has less flaws.

It beggars the question - if you could tie a 100% knot, would you want to? Personally I'd much rather the knot gave way before the line.

 UV Susceptibility of Nylon Monofilaments

The subject of UV damage to polyamides or nylon as it's more commonly known comes up frequently in forum discussions. Questions such as how long has it been in the shop, on the reel etc. While the UV susceptibility of nylon isn't disputed it's debatable whether it's significant as far as fishing line is concerned. Most studies of UV damage to nylon are over very long periods as in years under simulated conditions. A study done by the Textile Metrology Department at the University of Ludz in Poland over medium term exposure, ca 80 days, has shown that the tensile strength of polyamides can actually increase. You can read the study here INFLUENCE OF UV RADIATION ON POLYAMIDES.... Given that the tests were fibres exposed to the equivalent of unimpeded full daylight exposure, the likelihood of line incurring UV damage in a shop is bordering on non existent IMO. It's also unlikely IMO that line would suffer significant UV damage in normal use unless you're going to leave your line on year after year in which case the physical damage is likely to be far more significant than any due to UV degradation.

 Breaking Strain vs Shock Load

I haven't tested much main line but having had a mainline break when pulling for a break recently caused me to rethink things. I'd been testing some Daiwa Sensor 4lb and Shimano Aero Super Match 6lb which, despite wildly different published breaking strains are very similar lines in terms of the static wet breaking strain, around 5.7lb testing an 8" knotted length. As it happens I had some 4lb Maxima Chameleon. While I don't use it as I find it too heavy in the water (I've no hard evidence to support this) I decided to do the same test. Much to my surprise it turns out to be around 30%(1) weaker in relation to its diameter which incidentally is quite a lot bigger than stated on the spool. Maxima Chameleon is a hugely popular line and it's not uncommon to hear such as 'I've been using it 30 years and it's never let me down' and 'you could tow a truck with the stuff' and similar plaudits. Given that lots of Chameleon's fans are accomplished anglers there must be more to the stuff than just breaking strain. They can't all be suffering from A.N.M. (Acute Nostalgic Myopia).

Maxima Chameleon has a reputation as far as I can gather for being somewhat stretchy. I set up a simple test to see if there was a significant difference in the shock load tolerance of the three lines.

The test consisted of an 18" length of line suspended from the ceiling to which I attached a mass hanger whereby I could drop varying weights. The knots used were figure of eight loop knots. The mass hanger has a static weight of a little over 100g, as such the line is pre loaded.

The Maxima Chameleon, despite being around 30%(1) weaker in terms of static load can stand around a 30%(3) greater impact force. Given the number of fans Maxima Chameleon has the impact resistance of fishing line may be just as important as the static breaking strain.

The test wasn't intended to provide accurate quantifiable results. Merely to show whether there was a significant difference. I may at some point do a more detailed analysis.

(1) 30% is the percentage difference between the tensile strength of the materials which takes into account the difference in diameters of the lines tested, not the breaking strain as tabulated.

(2) Breaking strain determined by the average of 10 tests of an 8" length of fully wetted line tied with a 5 turn tucked half blood at each end to a 30lb Partridge micro swivel. Pressure is applied via a mandrel and measured with a load cell and custom electronics at ≅20°C.

(3) Taking into account the slightly larger diameter with an increased cross sectional area of ≅9.8%, 20% may be more realistic.

 Line Stretch

Purely for interest I did some stretch tests on lines. The initial length of the test piece was 1M. If you want the value as a percentage just divide the Y axis value by 10. The results are below:

The Maxima had a permanent increase in length of ≅3.6% the MAP Optimum ≅3.5% while the others showed less than 1%. With that in mind I pre stretched some of the Maxima by leaving it loaded with 1.3 Kg for an hour and then re tested. The dashed plot is the result.

With the diameters taken into consideration from least to most stretchy Nylon:

Again, purely out of curiosity I tested the breaking strain of pre stretched 4lb Maxima Chameleon. It wasn't any great surprise to find the average breaking strain had gone up by ≅9.6% over the unstretched tests. But in all but one of the ten tests the line broke rather than it breaking on the swivel which would be more usual. It might suggest that if you've been giving it a real punishing new line might not be a bad idea.