I often hear people telling me that a particular fly rod of theirs will not cast well. With a little probing, I can usually determine the main issue pretty quickly. I’m here to tell you a few secrets to making any fly rod work better to your liking…hopefully in layman’s terms so you can put these ideas into immediate practice and increase your success.
Both the forward and back casts work exactly the same. 
When a fly rod receives it’s rating (i.e. 5wt/Fast) the numbers are based on a test of that fly rod with the weight of 30 feet of a specific fly line (this base tells us it’s line weight…and can start as an arbitrary number). The amount the fly rod flexes as a percentage of distance from the tip tells us it’s action (Fast rods flex less than Moderate action fly rods).
Since a fly line has a specific weight per first 30 feet, based on AFTMA standards, it stands to reason that a certain length of fly line of a different weight will give us the exact same characteristics of action as what the fly rod is rated for.
One of my favorite small creek fly rods is a 2 weight, though I have never fished it with a 2 weight line. It is typically used on waters that are 10 – 15 feet across, so besides a leader it is rare for more than 15 feet of fly line to be outside the top guide. This fly rod is always fished with a 4 weight line under these conditions and performance is superb. The main goal being to have enough line weight to cause the fly rod to flex properly, which allows you to throw perfect loops.
When you are on large open water and trying to make a lot of long distance casts over 45 feet, do the opposite and drop your line weight one size to reduce the amount of weight you are trying to move through the air, while still having enough weight to flex the fly rod properly.
Another aspect of altering line weights allows us to affect the action of a fly rod. If you have a fly rod that is too fast for your liking (will not load the fly rod properly) try going up one line weight. The added weight, when compared to it’s rated line weight, for the same length of fly line will cause the fly rod to bend more deeply and effectively change the rated action. The same thing works for a fly rod that feels too soft…go down a line weight and the fly rod will effectively become faster in action.
For all of the reasons listed above, you will rarely find me with less than 2 spools for the fly reel I am using that particular day. It takes just a few minutes to swap a reel spool, install a different line weight and eliminate some of the frustrations of dealing with a particular piece of water.
