The Truth About Fluorocarbon, Part IV

NOTE: For future reference or referral, all 4 parts of this series have been edited and combined to make a single article which appears under the name 'The Truth About Fluorocarbon' in the articles section of the website, lower left hand sidebar.

So you read all the tourney reports in BASS or over at BassFan and it seems like all the pros are using fluorocarbon. There has to be a reason, right? These guys' livelihood depends on putting fish in the boat, and they'll take advantage of every little thing that might help tip the odds in their favor. So what gives? It primarily comes down to sensitivity in the end, along with energy transmission and absorption, so let's take a look at what is happening there.

There are a couple different concepts in play when considering how "bites" get registered by anglers, most all of which primarily encompass the functions of line tension, elasticity and linear density. Let's take a look at these 3 components and the role each plays.

Since we're dealing with a comparison of just two line types, each similar in diameter, each being fished on the same equipment and using the same lures, in a sense line tension is actually a wash in this scenario. One thing to keep in mind though is that for nylon lines, elasticity is a function of tension. So to get the best possible feel with monofilament line, you want to keep as much tension on the line as possible. Think of the old tin can telephone trick you learned as a kid.

Similarly, if we were to add braid to the discussion, tension would again come into play. Braid has very low elasticity, but it also has very low density. If you fish something like a Senko weightless on braid and give it slack line to fall, you won't feel a thing. What you will see is the line jump due to the very low stretch. On the other hand, if you fish baits that keep tension on the line due to the way they are worked, you'll have very good feel, better than either of the other two lines under the same conditions, again due to the very low level of stretch (very high modulus of elasticity, 30X-40X greater than mono or fluoro).

Speaking of elasticity, also referred to as modulus of elasticity, Young's modulus, or elastic modulus, it is a reference to the tendency of an object to deform along an axis when opposing forces are applied along that axis, or what might commonly be referred to as stretch or stiffness. As mentioned in a previous post, fluorocarbon and monofilaments are not too different here when tested off the shelf. This was demonstrated in the stetch test graphs I showed. As far as actual measurements go, most monofilaments core constituents fall in a range between 1.3-2.6 x 10~3 MPa, and fluorocarbon comes in at 2.1-2.9 x 10~3 MPa (FYI, braid is ~110 x 10~3 MPa).

But there is a catch. These numbers refer to dry sample tests, and if you remember from the previous post, nylons absorb water pretty heavily while fluorocarbons don't. This has a very definite effect on modulus. Water has a plasticizing effect that facilitates molecular chain movement. This decreases stiffness (modulus) but increases flexibility. Even a few tenths of a percent of water absorption by nylon can decrease significantly the modulus value of nylon compared to its dry state reading. How much? Depending on the specific formulation, as much as a 30-40% loss in axial elastic modulus and, therefore, stiffness.

The chart above demonstrates this in a quick way. I took two nearly 20' lengths of 15# test Big Game and soaked one of them for 2 hours in water and left the other one dry. I then ran a stretch test documenting % elongation relative to their original lengths at every 1/2-pound of pressure. You can see that the soaked strand stretched further as a percentage of original length at every strain tested. What isn't nearly as obvious is by how much relative to the dry readings.

With the first half pound of pressure, % elongation doubled. At one pound it was half (50%) as much. Between 1-2 pounds it averaged 30% higher readings. From 2-3 pounds it was just over 20% more. From there all the way through to 6.0 pounds it averaged about 12.5% more stretch than the dry line. As an over all average across all strains tested, there was a 27% increase in stretch when comparing th two lines. My guess is that with the standard 5 hours of soaking that I've seen stated as a test condition before, things would have looked worse. BTW, permanent deformity over the 20' of dry line was 1" after 6.5 pounds of strain, while the deformity in the wet line was 0.5" after the same strain.

So while the two lines in a dry state start out similarly and react as such, with fluoro having a slight overall advantage, nylon quickly absorbs water and it's properties change. Since fluorocarbon is nearly impervious to water, it's modulus properties and hence its stiffness or stretch don't. And this is where the difference comes into play, and where people correctly identify most fluorocarbons as being stiffer or having less stretch, as much as 1/2 less. They stretch a lot, it's just all relative, and they don't necessarily make the needed connection to use and subsequent water absorption. This extra stretch monofilament gains also turns into an energy absorber, dissipating the transfer of energy from a hookset.

The final component is mass per unit length, which is just linear density. Here as I have pointed out, there is a big difference. Monofilament density is ~1.1 while most fluorocarbons come in at 1.78. Again, water is the standard of comparison typically mentioned with a density of ~1.0. For simplicities sake, if we ignore terms like “modulus of elasticity” for a moment and just accept the following to be generally true: "The density of a molecular structure has a lot to do with its ability to transmit energy", it will go a long way in explaining this aspect. Think in terms of getting hit equally hard with a wood bat versus getting hit with a Nerf bat :)

You can transmit energy through basically solid media, more or less at the molecular level, without any obvious motion. A desk-top toy is the best example of this. Newton’s Cradle has a row of steel balls hanging on equal length strings which serve as pendulums. When one ball at the end of the row is dropped, the ball at the opposite end of the row will move, without any perceptible motion to the balls in the center. It's a demonstration of one of Newton's Laws concerning the conservation of momentum and energy.

Fluorocarbon is about 2/3 more dense than nylon monofilament and about 80% more dense than braid. This means that under similar tensions, the fluorocarbon would be better at transmitting that energy (of a bite) to the angler, and the angler using fluoro would be better at transmitting the energy from a hookset back down to the fish. It's why you can fish a bait with "slight" tension and feel the "pop" when a fish sucks it in.

So you can see that there are a variety of factors that come into play when considering why fluorocarbon is largely believed to be more sensitive than traditional monofilaments. If I had to rank them, I'd probably place density as the primary cause with "wet" modulus somewhere in second. Keeping a straighter connection to your bait due to line sinkage would be a small percentage in my opinion, at least until I see swimming pool or very clear lake pictures documenting otherwise. I think the pros have switched so heavily over to fluorocarbon because it gives them an advantage in the "feel"/hookset aspect of their game, regardless to what degree, while still having the stretch as a cushion of familiarity similar to mono when it comes to playing and landing a fish.

So that concludes my look at fluorocarbon line. It bears repeating that every brand of line has its own formulation that will affect all these parameters mentioned. As such, it's hard to make very specific claims without actually comparing a pair of lines head-to-head, and that's where you as an individual angler has to step in and determine if fluorocarbon, or any other type specialty line is right for your style of bass fishing.

Comments

[Paul Roberts]

Very nice. Best review of fishing line materials I've yet seen.

[Big Indiana Bass]

Thanks Paul...

I've condensed all 4 parts into one large piece and placed it under the 'Articles' sidebar on the left hand side of the page for future reference.

[Paul Roberts]

A comment: With a little patience, one CAN make use of that 3X sink rate and get a more straight line connection to the lure.

I fish shallow ponds a lot -often from shore. Mono and braid keep the lure bouncing upward on retrieves, whereas the fluoro sinks creating a deep belly that pulls more downward on the lure. This can be a disadvantage in really shallow or vegetated spots when I need to keep the lure up -mono or braid are better here.

[Big Indiana Bass]

Agreed. Anytime you can fish on a relatively shallow plane but want a presentation down in the water column, fluoro will probably work. With things like suspending cranks or jerkbaits, it can actually be a big help in keeping these baits down. I imagine it would work well for getting things like Senko's or trickworms to fall faster or stay down better without added weight.

I played around last weekend throwing frog baits in the slop with fluoro and it was a disaster. Braids are definitely the way to go with those type baits.

As a side note, I added a little under the 'Odds and Ends' section in the 'Articles' version of this piece concerning knots, thermal qualities and bending strength.

[Paul Roberts]

I'm thinking in terms of sensitivity -a straighter line to the lure. Sounds like some time at a swimming pool is in order.

I also have wondered about fluoro's apparent thinner diameter. At least per "rated" lb test on the box. What really needs to happen is an industry standard of disclosure: diameter and break strength (however that is done) on the box. Then they go ahead and describe the particular properties the given line offers.

[Big Indiana Bass]

A standard would be great, but I don't expect to ever see one. I've seen some independent testing and you can throw out any comparisons based upon "labeled" or "rated" pound test between lines. They don't exist except as a generality. Fluoros appearing to be thinner than monos for a rated pound test is merely a marketing ploy.

Interestingly, and not surprisingly, at least not to me, there is a 75% correlation between diameter and break strength in fluorocarbons, and a 70% correlation between break strength and stretch. However, the relatoinship breaks down to less than 50% when comparing stretch to diameter. Additionally, fluorocarbon break strength when compared to monos of equal diameter is consistently 75% less than the monos.

Reads like another post in the making ;) Also got my hands on some cool UV degradation studies of monofilament.