Posts Tagged ‘Matching fly rods and lines’

AFTM Numbers

May 15, 2022

What’s this?
A new initiative to post some information primarily designed for novice fly anglers, if you see “The Beginners Page Logo” it means that the post is primarily designed to help novice anglers but of course everyone is welcome to read and comment. I hope that you will, it might help end up with a better product overall.

The Beginner’s Page logo is designed to show that the post is primarily aimed at novice anglers.

The Beginner’s Pages: The AFTM system, it seems logical and sensible but the system has real problems which you should understand, at least a bit.

The AFTM system is nominally a means of matching line weights to the rod and on the face of it a pretty simple and sensible way of doing that. AFTM stands for Association of Fishing Tackle Manufacturers.  

You will almost definitely be aware that at least to some degree “the line should match the rod”, that is to say that if you are casting a weighted line then you need a suitable rod to cast that particular weight most effectively.

So, the AFTM system is designed to provide at least some sort of guidance as to which line to cast on which rod. The system defines the mass of any given fly line based on the weight of the first 30’ of line (excluding any level portion at the front) by measuring that weight in grains and then converting to a simple number.

In case you are wondering, a grain is a pretty small measurement of mass; approximately 64.79 milligrams. There are a thousand milligrams in a gram and a million in a kilogram. There are then approximately 15432 grains in a kilogram. Grains are small amounts of mass, that’s the point.

Taking the lines, weighing them and giving them a number is at least objective, you should find that any line measured as, let’s say, a five-weight line, should perform similarly to any other line with the same AFTM rating. You do know at least that the first 30’ should weigh the same.  (We will see in a minute that all is not necessarily as it seems, but at least we have a pretty objective test to start with).

The second part of the equation is that every fly rod has a designated AFTM rating supposedly showing the ideal line weight to be used with that rod, again it seems pretty straightforward, except that whereas the weight of the line is at least measured in some sort of scientific manner the designation on the rod is little more than a guess. There is no standardized means of determining if a rod is a #4 or #9, so unlike the weight of the line the designation written on the rod is highly subjective, pretty much just the opinion of the rod builder.

Much of the time that will still suffice for the novice angler, and as a base point it is probably the best option to simply mate the rod designation with a line of the same designation. (It is highly recommended that if you are a novice, you get some help from the guys at your local fly shop).

Where the problems come in:

Firstly: there is a very simply issue and that is that there is no standard as to what line casts best with which rod, one angler may prefer this and another angler prefer that. Not to mention the guy on a small stream is casting a lot less line than the angler on the side of a lake. In reality you can (perhaps with some difficulty) cast any line on any rod, so the numbers aren’t set in stone. 

Secondly: The line weights as designated #4, #5, #6 etc include lines within a band of weights, so, even measured correctly two different #5 weight lines may not actually have the same weight for the first 30’. Looking at the table above you can see that the maximum variation for a #5 line to still be a #5 line is approximately 8%. Imagine if you and your mate both ordered a beer and your glass contained 8% less beer than his, you might feel rightfully miffed. 8% is a pretty large variation.

Thirdly: Even if the weight of the first 30’ of two different lines is exactly the same there is the issue of the taper. The taper, is the shape of the fly line; fly lines are universally tapered, they don’t work properly if they are not. But there are hundreds of variations of taper, usually designed for different casting or fishing situations. In essence what the taper and the AFTMA number mean is that if you are casting 30’ you should be casting the same overall mass. BUT, and it is a big BUT, if you are casting 20’ of line with two different #4 fly lines the mass most likely won’t be the same.

Fourthly: There is no clear means of defining which rod works best with which line, for a start, a lot of that is up to the caster, the way they cast, the distance they want to cast etc.
In fly casting, it should be obvious that there is no one ideal weight to be casting with any given rod. We are casting different distances all the time and as the line has mass each time we change the distance we change the mass we are throwing. So, with the best will in the world there is no ONE weight that can be said to be correct. (if lines were level and not tapered a #5 line would weigh 4.66 grains per foot. If you cast 30ft the line would weigh 139.8  grains and would behave like a  #5 weight, BUT, if you cast 35ft it would weigh 163 grains equivalent to a line designated as #6 weight. As Simon Gawesworth at RIO fly lines often explains, the difference between a #5 and a #6 line at 30’ is about the mass of a standard business card !!! (about 25 grains). The whole system, although at first glance simple, is actually complicated and confusing I admit.

MORE PROBLEMS:

The above issues are problems which are entirely built into the system as it stands, an error allowance of something like 8% and the fact that we cast different distances and therefore different mass all the time. Plus that there is no specific means of measuring the AFTM number of a rod in the first place, that all makes it more tricky that it looks at first, however there are further problems with the way it all works.

For some time, fly rod manufacturers have been driving demand for what they refer to as “fast action rods”, supposedly they recover from bending more efficiently but at the same time they are to all intents and purposes simply stiffer. Perhaps one way of doing so, although I couldn’t prove this actually happens, would be to simply take a rod that was previously designated as a #5 weight and call it a #4 weight. With a #4 line on it, it would seem stiffer when casting and this has been something of a trend now over a number of years. One equally needs to bear in mind that fly rods are flexible levers which bend in a progressive manner, the more force applied the more they bend into thicker sections of the blank, so again there is no ONE answer to what mass works best. Push that too far and the average angler can’t cast rods that are that stiff, (fundamentally because they don’t match up well to the lines being used).

So, the line manufacturers started to come up with lines which are heavier than designated by AFTM. Generally, they give them some sort of additional notation such as AFTM + or similar, but in effect they are cheating the system. Also, they often don’t tell you, so you have no idea that your lovely and easily cast #5 weight line is in fact a #6 with a different label on it. (I have to admit though that the line manufacturers have to some degree been pushed into this by the rod manufacturers, because actually few people can cast these “fast” action rods, which they keep pushing, without “overloading” them)

As a general rule, particularly if you are a novice ,it feels much easier to cast a line heavier than the one specified on the rod, a LOT of that is due to poor casting technique but one expects that with a beginner. What has happened though is that this “overloading” either intentionally or otherwise has become almost standard.

It is a bit of a joke because the rod manufacturers are all saying “people want fast action rods” and the line manufacturers are saying “overload them to slow them down”.. Who is right?

I would still say that as a general rule if you are a novice you should go with a line nominally rated the same as the rod, if you can get expert advice from a pal, the fly shop or whatever go with that. But beware, what was once a rather subjective but at least simple system has become a minefield of complexity and I might be tempted to add, dishonesty too.

As things stand, about the best that can be said for the system is that it offers a loose guideline to matching lines and rods, a very loose one. If it is at all possible you want to test out different lines with different rods before you purchase them. Equally if you are a novice, I highly recommend that you don’t get trapped by the “fast action rods are better” mantra of the marketing department. It is true that they perform more effectively when an expert caster is aiming to cast the furthest in a casting competition, but that in no way relates to what you generally want when on the water.

The top end of competition but not much good for a trip to the shops.

It may well be the case that Lewis Hamilton’s Formula One Mercedes is the quickest thing on the road, one could reasonably perhaps prove that to be true. However, it probably isn’t going to be the ideal transportation for a family of four, heading to the shops for some retail therapy. Even if you could manage not to stall it when leaving the driveway, where would you put your parcels? or for that matter the kids? The point is that what might arguably be “the best” in one situation, is undoubtedly NOT the best in another. Super fast (stiff) fly rods used for distance casting competition have no place out fishing and there is little if any reason to assume that they would be of any benefit to the angler, novice or not.

To my way of thinking this obsession with super fast action rods simply doesn’t make sense when compared to most fishing situations, after all, these things are fishing rods not casting rods. They need to provide the angler with some “feel” and control and to be able to perform at different distances with some level of comfort. In general rod and line combinations which are “slower” in action and provide more feel for the caster, particularly the novice caster, are going to perform better and feel much more pleasant to fish.

For a more humorous discussion on the subject you may also enjoy reading a post from this blog from some time back. https://paracaddis.wordpress.com/2012/03/15/an-aftma-fairy-tale/