Information Courtesy of Capt
Fly rods are classified by line weights, a designation of how strong the rod is. Your choice of rod weight will be dictated by two items:
1) The size of the fish you will fight and need to lift to the surface or…
2) The size fly you will need to cast.
Choose the heavier rod from the two choices. For instance tarpon flies are small and can easily be cast on a rod too light to fight the fish.
The most common in-shore rod ratings used are 7-8 & 9 weight rods. These rods weights will handle most sea breeze winds so you can make a cast and are sufficient to subdue most common fish such as trout, redfish, snook, bonefish, spanish mackerel etc. The fly fisherman who chases tarpon will commonly use a 10 weight rod for smaller back country fish and will want a 12 weight rod when fishing the spring migration of adult fish of 100+ pounds.
AFFTMA (American Fly Fishing Tackle Manufactures Association) has an established standard for line ratings based on the weight of the first 30 feet of the fly line in grains.
Rods are rated based on how well the rod casts 30 feet (9.1 M) of designated fly line outside the tip of the rod. This standard has gotten a little “fuzzy” over time since fly rods are now capable of casting more line. It has been suggested that manufactures now label a rods weight on how well it casts 40 – 50 feet of line or more. Today it is not uncommon to “up-line” a rod by using a line one weight heavier than the rods designation, especially if most of your casts are short.
Dual rated rods handle more that one line weight (as all rods can). They once were more common but are still found today, usually on less expensive rods. Which line is used on dual rated rods depends on the distance of your typical cast i.e.…less than or greater than 30 feet.
Line Weight Ratings in Grains – AFFTA
|LINE NUMBER||WEIGHT (GRAINS / 30’)||TOLERANCE|
|1||60||+ OR – 6 GRAINS|
|2||80||+ OR – 6 GRAINS|
|3||100||+ OR – 6 GRAINS|
|4||120||+ OR – 6 GRAINS|
|5||140||+ OR – 6 GRAINS|
|6||160||+ OR – 8 GRAINS|
|7||185||+ OR – 8 GRAINS|
|8||210||+ OR – 8 GRAINS|
|9||240||+ OR – 10 GRAINS|
|10||280||+ OR – 10 GRAINS|
|11||330||+ OR – 12 GRAINS|
|12||380||+ OR – 12 GRAINS|
|13||450||+ OR – 15 GRAINS|
|14||500||+ OR – 15 GRAINS|
|15||550||+ OR – 15 GRAINS|
Note: 1 Grain = 64.8 milligrams
All rods must be able to handle a wide variety of line weights while casting. Let’s take a 6 wt. fly rod as an example. Per AFFTA, the first 30′ of a 6 weight fly line is 160 grains. If you are casting with half that much or only 15′ of fly line it would weight only 80 grains which is equal to only a two weight line. What happens when you make a distance cast to 70 feet? We know that the first 30′ of our 6 weight line weighs 160 grains, but carrying another 40 feet of running line in the air (at approximately 3 grains per foot x 40 feet = another 120 grains) for a total weight of 280 grains of fly line. That is equal to casting a 10 weight!