Since fly line is so thick and visible, you don't tie the fly directly to it. You must use a leader which is comprised of different diameter lines such as monofilament or fluorocarbon. Using a leader not only allows you to actually tie on the fly, but it also allows the fly to be presented in the most natural manner possible. There is no ONE leader for all species and situations, so you must tailor the configuration to your specific fishing.
A leader is typically tapered; it starts off thick and ends thin. Leaders can be purchased knotless or can be constructed using different lines tied together in a certain order to form the taper. Along with a good cast, the right leader will propel the fly away from the end of the fly line. Having this proper "turnover" is important for getting a solid presentation.
The size of the fly and the stiffness of the leader will impact the ease of turnover. A long leader tapering to a supple tippet may be perfect for presenting a tiny #18 dry fly in a quiet creek, but it won't be good for tossing a much bulkier fly. A stiffer, shorter leader will transfer energy from the fly line more effectively for better turnover of larger flies.
Sections of a Tapered Leader
Butt: This is the only section that is directly joined to the fly line. The butt section is the thickest portion of the leader and is usually made from stiff line that is about the same stiffness as the fly line. Turnover power increases as the length of the butt section increases, while too short of a butt section in relation to the midsection and tippet may not provide proper turnover power for heavy flies.
Midsection: The midsection is the middle of the leader and helps transfer energy from the stiff, thick butt portion to the more supple, thinner tippet. A long midsection and/or tippet can help provide a softer presentation and more natural drifts.
Tippet: This is the thinnest end of the leader where the fly is tied onto.
A few variables come into play here including the type of fly line being used and size of the fly. Leaders can commonly range from just a few feet to well over 10-feet, but a length around 9-feet is a pretty standard starting point for many situations with a floating line. With sinking fly lines, leaders are typically on the shorter end of the spectrum for two good reasons: a shorter leader allows the sinking fly line to pull the fly down faster, and sinking lines usually have naturally-colored sinking portions that likely won't spook fish as readily.
As eluded to earlier, a tapered leader has a gradual transition of diameter/poundage/stiffness throughout its taper. Folks make them in many different combinations, but an old baseline formula is the 60/20/20 rule. This means you'd use a butt section that's 60% of the length of the entire leader, followed by 20% midsection and 20% tippet lengths. To briefly model this formula, the following is a very basic example of a 10-foot leader and its corresponding (diameters) in inches:
Butt Section: 6-feet of 25-pound (0.024")
Midsection: 2-feet of 20-pound (0.021")
Tippet: 2-feet of 16-pound (0.018")
Despite the simplistic example, the leader is often constructed not just with different overall lengths and varying section lengths, but it may also use more pieces of line per section as shown above. The leader will still have the 3 main sections, but more than 1 piece of line will be used per section to achieve the gradual, progressive taper down to the tippet. This can be especially common if trying to create a taper down to a very fine diameter tippet. With these delicate leaders, presentation and knot strength can suffer if the difference in diameter between each piece (especially in the lighter midsection to tippet portions) is too great, so extra pieces are used to keep the taper more gradual. Tying a leader like this can be quite a chore, but knotless leaders provide a nice alternative....read about them below!
Tippet materials are labeled by their breaking strength in pounds and some also carry a numerical "X-rating" on the package that's based on the diameter. Packaged tapered leaders will also show this X-rating to represent the tippet diameter used in the leader. Below is a breakdown of common X-ratings to their equivalent diameters (in inches):
0X = 0.011
1X = 0.010
2X = 0.009
3X = 0.008
4X = 0.007
5X = 0.006
6X = 0.005
7X = 0.004
8X = 0.003
- Each time the X-rating goes up, the diameter decreases by 0.001.
- A fast way to determine diameter is to minus the X-rating from where the scale begins at 0.011. So, a 7X tippet is 0.004 in diameter because 11-7=4.
- Heavier/thicker tippets (like those commonly used in saltwater) are often just referred to by their breaking strength rather than an X-rating.
- The X-rating of a certain tippet size won't always be rated at the same poundage. For instance, a 4X tippet from a certain series may be weaker than the 4X tippet of a different series from the same or another manufacturer.
Aside from constructing your own leaders, knotless leaders are convenient options. These one-piece leaders are already tapered so there's no wasted time tying knots and thus no extra knots to hang up in your rod guides or get fouled by debris. A spare tippet spool or two is good to carry, though. Knotless leaders only have so much tippet portion built-in, and after you change flies a bunch of times the tippet gets too short. In many cases, it's actually a good idea to add on a length of your own tippet to the end of the leader before the first cast is even made. This gives you more tippet to play with and makes for better drifts with small flies.
Nylon Mono vs. Fluoro
Common nylon monofilament is generally cheaper in price than fluorocarbon. For many instances it works fine as long as you choose the line size properly. With that said, fluorocarbon is often touted to offer advantages like added durability, less stretch, and less visibility to the fish which makes it very popular. Fluorocarbon also sinks slightly faster than regular monofilament which can be a good thing depending on where and how you're fishing.