Underline or Overline (24 of 35)
How many line sizes can a fly rod handle? Can you underline or overline a fly rod? What will going up or down on a line size do to a fly rod, and how will it affect your casting? In this short video, Tom Rosenbauer shows what happens when you change line sizes, and gives you reasons for doing it—and when not to do it!
Video Transcript:
So, what is line weight and why is it important?
Line weight is important for two reasons. One, that it needs to make your rod flex. Because when you cast a fly rod, the line needs to bend that rod enough to build up some energy to drive it out there. Now, I have a four-weight rod here. Four-weight is a fairly light line. It's used for smaller flies. And a four-weight line gives you a lot of delicacy when you put a fly on the water. So, it doesn't spook fish, it doesn't land very hard. And that's great. And this four-weight rod handles this four-weight line really well. Manufacturers build their rods to a specific line weight. Now, if I were throwing a really big heavy fly, then I might wanna go to a five or a six or even a seven-weight rod because the bigger mass of those heavier fly lines will throw those bigger or more air-resistant flies better. But here, for this rod, I'm gonna fish small flies, nice delicate presentation. And the rod handles the line really well. Even in this wind we have today, I can make a nice cast and I can deliver that fly where I want it to go with this four-weight.
Now, can you overline a fly rod? Yes. You can overline a fly rod. I could probably put a five-weight on here and be okay. What's gonna happen when you overline a fly rod is that it's gonna slow down the rod a little bit. The rod is gonna bend a little bit more. Casting motions might be a little bit easier, but you're gonna struggle on longer cast. So, you can overweight a rod by about one line size. Depending on the manufacturer. You have to try each rod with a heavier line. Now, can you underline a fly rod? That's a different question. When you underline a fly rod, that fly rod isn't gonna flex enough. It's not gonna develop that energy. When you underline a fly rod, you're gonna have to work harder. You're gonna have to push that rod to get that line out there. So, underlining isn't such a great idea. Overlining by one size may work okay for you. So, let's put a five-weight line on this four-weight rod, see how it works. And then we'll put a six-weight line on here and see how that looks.
Okay. So, now I've got a five-weight line on this four-weight rod, and it's pretty pleasant. Got a lot of wind, I can still drive it into the wind. But when I start to pull more line and try to make a long cast, the rod is gonna start bending a little bit more and it's gonna put a little bit more stress on that rod. It's not gonna hurt the rod, but I'm just gonna struggle when I'm trying to throw a really long cast. So, graded short distances, it's gonna work just fine. I kinda like it. I still like the four-weight line better, but the five-weight line will definitely work on this rod.
So, now, I have a six-weight line on a four-weight rod. Let's see how this goes. So, again, just like with the five, in short, it's fine. If I'm 15, 20 feet out there, yeah, it works well. Let's pull a little bit more line off here and see what happens. And it's working. You can make it work, but it's starting to flex that rod a little bit too much, it's starting to bounce a little bit. It's kind of overloading that rod and I can see where... I wouldn't wanna fish this all day long. But you can make it work if that's all you got. It depends on the fly rod, it depends on the design of the rod, but some rods will handle a couple of line sizes.
Now, I'm purposely underlining a rod. I've got my four-weight line on my six-weight rod. See how that goes. And yeah, you know, you can make it work. You can throw this four-weight line on this six-weight rod, but I really have to force the rod to get that rod to bend because there just isn't enough mass to bend the rod. And the rod really has to bend for you to cast properly. So, I have to push it. I have to push it a little bit harder. And yeah, you could fish this way for a day. You could make it work, but it's hard work. It's a struggle. You just have to get that rod to bend, you just have to push that rod harder. So, you can underline a rod, you can overline a rod within one line size, not too bad. But if you're gonna air in one direction, I would go with overlining a rod by a line size or maybe two, depending on the rod.
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Did you get all that? Aargh, too bad. Well, we got the fish anyway.
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