Recently I happened upon two pieces of information, an article and a catalogue, which got me thinking about how difficult it can now be to choose a weight forward fly line to match a particular fly rod, especially the newer fast action models.

The article was “Line ’em up” and it was written by the late Hugh McDowell for Fish & Game NZ back in 2002. It is an excellent summary of the issues faced in selecting fly lines and is possibly even more relevant today. McDowell used the experiences of a novice, an angler switching from fibreglass to carbon fibre and another angler switching from cane to carbon fibre to illustrate the importance of over lining the fly rod to improve flex and casting performance.

The catalogue was the Scientific Anglers 2015 fly line catalogue which showcases 61 pages of fly lines for just about every fly fishing scenario imaginable. This is the range of offerings from a single fly line manufacturer and this is mirrored by several of the other big players. The fly line options available today are mind boggling.

McDowall starts with the following two paragraphs:-

“If you look at the shaft of your fly rod just above the cork grip, you’ll almost certainly see a figure somewhere between 5 and 10 printed there, possibly preceded by the letters AFTMA, or perhaps something like “Recommended Line Weight”. Do you know what that means? Of course you do. It’s the best line weight to use on that particular rod, isn’t it? Everybody knows that and everything you’ve ever read on the subject confirms it. Until know that is, because I’m about to tell you that, just like the old song says: “It ain’t necessarily so”…

I’m not saying that it isn’t a good choice, because it usually is. What I am saying is that its not necessarily the best choice for you. You see, although the people who designed and built your rod are certainly both experienced and extremely competent casters, they cannot possibly tell exactly the circumstances involving how the rod will be used, or what level of experience the ultimate owner will have. And herein lies the problem”.

Fly rods are no different from spinning rods in that they have a progressive action and require a certain amount of weight and angler input to load and cast. The greater the mass used to bend the rod, the more the rod flexes. In fly fishing it is the fly line that must generate this flex and that is why the head (or front portion) needs to be weighted. Remember that there are two ways to force a greater flex into the rod, either casting with a heavier line or by aerialising more line outside the rod tip.

Depending on the fly you are casting and the fishing situation encountered it may be necessary to cast lines of varying weights. The AFTMA system was devised to properly match various weight lines to the rods that would best cast them. The system is based on the first 9 metres (30 feet) of line. Once this distance and weight was fixed it became a simple task to design specific rods that would work best with 9 metres of any specific line past the rod tip. The AFTMA line weights are shown in the table below:-

In 2002 McDowall used the table below to illustrate the anticipated casting range for each line weight. What is fascinating is that now fly rod manufacturers are designing #6 and #7 weight rods to cast much further and this has lead to some interesting changes in fly line construction.

In weight forward lines it used to be common for the head (or front taper) to be roughly 9 metres (30′) long and match the AFTMA line rating. However nowadays head lengths can range from 9 – 19.5 metres (30 – 64′) which means that you need to be careful how much of the head is outside of the rod tip during false casting.

For example, I have a Hardy Sirrus # 9 weight rod that was manufactured around 2004 and if I pair it with a #9 weight Airflo Ego Distance taper fly line with an 19.5 metre (64′) head then it flexes too much and the action becomes sluggish if all of the head is outside of the rod tip. In fact it casts best when only half of the head (30′) is outside of the rod tip. The rod is probably incapable of handling this line even though it is correctly weighted. The maximum casting distance with only half of the head aerialised is significantly less than the length of the fly line which is roughly 36 metres (120′).

Just to show how tricky all of this can be I also have a Kilwell Xantu #8 weight fly rod that can easily cast the same #9 weight Airflo Ego Distance taper without any problem. Casts over 100′ are routine with a minimal double haul. Why can a rod that is rated at #8 do something that a rod that is rated at #9 cannot? It just shows how far technology has moved in the last 10 years and how much variation there is in the AFTMA system.

I am also fishing a #7 – 8 weight Airflo Ridge Clear Slow sink Intermediate line on my Kilwell Xantu #6 Weight fly rod without any issue. Distance is critical when fishing on the saltwater flats and it is often windy. Using a slightly heavier line with a longer head makes casting into the wind so much easier.

The trick to understanding which fly line suits the rod you have and the situation you are fishing is to learn to fly cast by feel and use this to determine the optimum flex profile of the rod to suit your casting style. This is explained in detail in:- https://activeanglingnz.com/2015/11/30/fly-casting-by-feel/

The simplest way to make sense of all of this is to select a rod to suit the distance that you are most likely to be casting using the table above. Then choose an AFTMA line rated to suit the rod, preferably with a 9 – 12 metre (30 – 40′) head. If the rod has a fast action and you prefer one with slightly more flex then either up size the line weight by at least one (i.e. #6 instead of #5 on a rod rated for a #5) or choose a correctly weighted line with a longer head length.

Some dry fly anglers who are worried about presentation with weight forward lines drop the line weight by one AFTMA number and simply aerialise more line as by doing this they can bend the rod just as fully as otherwise, but they now have a thinner and therefore more aerodynamic fly line. The other option, that is more common, is to switch to a double taper line as these are generally thinner in the front third of the line and alight more gently, especially at close quarters.

I’ll leave the final word to Hugh McDowell:-

“Nevertheless if you’re experiencing casting problems, often a move up to a heavier line will make a surprising difference. I know fly lines are relatively expensive, but you can probably borrow a couple of different weights to the one you are currently using. Friends, or perhaps someone in your angling club, may be able to help you try a few experimental casts before you splash out. But do try it. You might well be astonished at the results”.