A Post About Nylon Casting LInes

Nylon lines in tenkara intrigue me. One of the lines that helped me make the transition from furled lines to fluorocarbon level lines was a tapered nylon line. At that point in time I didn’t really understand much about the differences in materials. I recall reading a post on the Discover Tenkara website about how nylon level line could really help with one’s casting because it is notoriously difficult to cast and tends to highlight faults in one's technique.

As I’ve put more years behind me and gained experience fishing with a tenkara rod, I have come to try quite a few different casting lines. I’ve experimented with different profiles, tapers, materials, and compositions. Recently I have recently spent some time exploring some little nuances revolving around nylon lines. More specifically, how soaking the line changes how we interact with the line.

I think a good place to start is with the “why?” of it all…

Why Use a Nylon Casting LIne?

Nylon fishing line is less dense than fluorocarbon, making it both lighter and more buoyant. When comparing a section of #3 nylon level line to an equivalent diameter #3 fluorocarbon level line*, the nylon weighs in at just under 0.007g (0.0068g to be exact) per 10cm, while the fluorocarbon line weighs in at 0.013g per 10cm. So what is the benefit of having nylon line that weighs about half of what fluorocarbon line does in the same length? Less sag.

With less sag, your flies are less influenced by the weight of the line when trying to suspend the fly in the current - whether it’s in a riffle, or an eddy near the bank. Less influence from the line will offer a more natural drift when the angler seeks it.

Of course, there is a flipside to contrast the benefits of a light line. The first drawback is that nylon line holds more memory, so you’re more likely to have your line coming off the spool with a significant amount of coil that needs to be stretched out if you want to fish with a straight line. Along with that, a lighter and less dense line is noticeably harder to cast.

But… There may be a way to get somewhat of a compromise…

(*For the fluorocarbon line, I had to measure a few lines to find one that was actually the same diameter as a few that are labeled as 3 Gou actually had the diameter of 3.5 Gou.)

Nylon Line and Water Weight

Because nylon line is absorbent (to a certain degree), the weight and flexibility of the line will change over a fishing session.

According to the internet, nylon line can absorb about 10% of its weight in water. When the comparison between the two material of lines shows that the nylon level line weighs only 51% of the same measured diameter* of fluorocarbon level line, a 10% increase in weight will still have you fishing at 61% the weight of fluorocarbon.

Along with the added weight, which may make it easier to cast a nylon line, the water absorbed into the line also makes the line more supple.

So what is the best way to get the line to absorb water if one wants the benefits that come with a little more weight and suppleness?

Of course, you could just go about your fishing and let your line absorb what it will over the duration of your fishing session, but this would mean only part of your line would absorb water. The other option is what seems to be a common practice amongst anglers in Japan - soaking your nylon line prior to fishing.

Testing Water Absorption

In order to gain a better understanding of how much water nylon line really absorbs, and how it may affect the use of the line I decided to break out a few tools and do a little test before actually casting some lines. In this first test I compared the two lines I referred to earlier. 

I cut a couple 10cm sections of the Sunline - Troutist Wild 3 Gou Line. The diameter of the line is 0.285mm (True to advertised Gou), and the weight per 10cm is 0.007g. After getting the base measurements, I soaked two sections in two separate containers - one with room temperature water, and the other with warm water (98F). I set a timer for 10 minutes, weighing and measuring the diameter of the line after 3 intervals over 30 minutes total time.

After 10 minutes, both sections (room temp, and warm water) weighed in at 0.008g with no change to the diameter. There were no changes at the 20 minute, or 30 minute timers. 

The initial test shows a little over 14% increase after the first 10 minute soak.

While the weight did increase by 0.001g for the 10cm section of line there was no difference in water absorption between the room temperature and warm water soak as far as the weight goes. I will mention though, that the line soaking in the warm water was noticeably softer than the room temp soak.

Comparing The Numbers

As for a fluorocarbon level line of the same diameter, I found Tenkara USA’s 2.5 Level Line to have the same diameter (0.285mm), and a weight of 0.013g for a 10cm section.

To help put it all into perspective, if we were to attach a 360cm fluorocarbon level line using the Tenkara USA line mentioned above, the casting line itself would weigh 0.472 grams. It’s really not a lot of weight. But, if we compare it to the same length of dry nylon level line from Sunline, you would have a casting line that weighs 0.244 grams.

While this may be a tough line to cast being that it is so light, you could soak the line and get a weight of 0.288 grams for the 360cm length. Not a huge increase, but it may help.

Casting a "Saturated" Line

All the numbers and mathematics are really only part of a bigger picture. I think they’re more helpful when we can use them to associate the feel of something in a way that helps us understand how it all translates. To do so, we gotta cast it, and preferably fish it.

Before I get into it, I have to recommend that you, the reader, try this yourself if you’re at all interested and able to get your hands on some form of nylon line.

At home, I took some time out of my morning to cut a 320cm length of line that weighed in at 0.227g by itself (dry). I then went into the yard and cast it using three rods - Tenkara Tanuki Ninja 2 (350cm), Nissin Royal Stage 7:3 (320cm), and the Tenkara Tanuki Kunoichi (310cm).

Starting with the 350cm rod, the casting felt very manageable. So I went to the 320cm rod, and after a little adjustment of my casting stroke I was able to find the feedback in the cast that I was looking for. Lastly, I tried the 310cm to see if it was going to be any more difficult with the line being slightly longer than the rod, and found it was almost easier than the 320cm, but that’s probably just how the rod loads and flexes.

After casting the dry nylon line with all three rods, I soaked the line for 10 minutes and weighed it, recording a new total weight of 0.284 grams - a 25% increase in weight this time.

I went out and cast it with the three rods. I didn’t expect to notice as much of a difference with the 350cm rod, but the line was clearly more supple and seemed to cast a little smoother. This was the experience with the other two rods as well, and the line did feel easier to cast with both the 320 and the 310.

Fishing With The LIne

It seemed logical that the next step would be to go out and fish with the line, both dry and soaked. During the session, I only used the 320cm rod just for consistency purposes. The casting of the line changed when a fly went on to the end. I started with a size 12 futsu kebari at the end of a section of tippet tied to the dry nylon line and immediately noticed the line didn’t quite push the fly in the same way a fluorocarbon line, or thicker nylon line would. The amount of sag and influence the line had on the fly was very minimal.

After the futsu, I switched to a size 14 soft hackle to see if the line would have much influence on a smaller fly with less characteristics that anchor it in the current. It cast a little easier, and drifted well with very little influence.

I then soaked the line for a little bit and tried both flies again while fishing the same runs. In all honesty, I didn’t notice much of a difference in performance with the line soaked. Yes, it was more supple, but it didn’t really change the difficulty of the cast, or the amount of influence over the fly. I did notice that the line did dry relatively quickly in the 87f heat, bringing it back to a more rigid state. I even played around with soaking the lower third of the line closest to the fly to see if it would change how well it anchored, but found little to no difference in the drifts.

I did hook up on a couple fish, but felt I didn’t quite get a good hook set and the two fish both spit the hook after very brief fights. It’s hard to say if the gentle hook set was due to stretch in the line or just poor timing or technique. But this brings up something else to consider when soaking the lines…

The Downsides of a "Saturated" Nylon LIne

Of course there are downsides. With water absorbed, the line will lose a portion of its tensile strength. The internet suggests a 25% or more reduction in the line strength. 

The extra water also changes the stretch of the line. Though, I did measure the line again after soaking it at home and saw no change in length - but I did not pull on it in any way. Having a fish on the line may change that. I also measured the diameter of the line again after it was soaked and saw no change in the diameter.

One last disadvantage to soaking the line is just the overall durability of the line decreases. I think that is reflected in the amount of stretch and decrease in tensile strength that is said to take place, but with a softer line also comes less resistance to abrasion.

Final Thoughts

I will say that after fishing with a thin and light nylon level line, I could see where it would have a place in slow moving streams where you want a delicate presentation of a small fly. Even with a bigger fly hinging during my casts, I noticed how little the line affected the drift after the fly was in the water. But… I don’t see myself utilizing this #3 nylon level line often.

I say this because I am someone who enjoys casting. I like having a line that pairs well with the rod in a way that makes the experience of casting smooth and as close to effortless as it can be. With that, I don’t see the perks of an extremely light line outweighing (or underweighing) the performance of a line that is maybe a little heavier.

With that said, I do really enjoy fishing the tapered nylon lines offered by Fujino. I have found them to work well with my casting stroke in many situations. They are responsive in times when I may need to make more creative casts to get the fly into tricky spots. Yes, they are thicker and ultimately heavier than fluorocarbon level line in many instances, but I still find them very enjoyable to fish.