How to fly cast is the subject of many books small and large. I choose to give a short description of a basic fly cast, but this text does not cover the subject of fly casting fully. It only serves as an introduction.
The longer your rod the farther you can cast. We can manage 11′ one handed but rods longer than that become difficult to manage with one hand. The magic rod length for one handed casting seems to be 9′ for normal sized folks.
You can cast a line with a broomstick. The Inuit use an Atlatl to cast their spears. The Atlatl becomes an extension of their arm, so the casting stroke becomes longer.
When we load or bend a rod it shortens (measured from tiptop to handle). Then it straightens on the forward cast thus we can view it as spring. Now we can say that our rod is a lever with a spring action. When a bent or loaded rod unloads on the forward cast it will become straight (RSP – rod straight position), then it flexes past the RSP and then it recoils to the RSP again. The best rods are those that are damped with small oscillations, but all rods will oscillate. The sequence runs like this. We cast the line behind us and the rod straightens. Now as we move it forward it will bend (load) against the resistance of the line behind. The rod tip moves in a straight line and then we stop the rod. and it straightens again. The path that the rod tip traces out should be as straight as possible in both the vertical and the horizontal plane. The backcast and the forward cast must adhere to the 180-degree rule i.e. both in the same straight line.
The bent or loaded rod casts the line when the top straightens. The best casters can stop the rod “on a dime” but beginners will have a slower softer stop. Imagine you are driving your car at 45 mph and you slam the brakes. The car itself will stop but you will be pushed against the seat belt and loose objects in the car will fly forward. (Rod is car and the fly line are you and the loose objects in the car). The harder the stop, the faster and farther the line will travel over the rod tip and form a loop. The more bend or load in the rod the longer we cast. The loading of the rod is important and the speed by which the top straightens is important for the length of the cast.
Our goal when casting is to produce a straight top leg, that leads to a narrow aerodynamic loop when the rod tip is “stopped on a dime”. When we load the rod, and stop it, the line starts to travel over the rod tip and the loop forms. If we pull the rod tip down, we will open our loop which will result in a wide loop that does not travel far. The loop itself is a result of our movements and the properties of the rod.
The upper part of the loop is the fly leg and the lower part is the rod leg. The leading part of the line is the loop. The fly leg needs to be straight for a good cast.
When we cast a stone, we follow through with our arm in the direction of the cast. If we do that when fly casting the loop becomes wide and inefficient. Beginners should try to stop their hand hard and high to produce a narrow loop. Stop the hand hard at about eye level and keep the rod high then a narrow loop will roll out.
The pick-up and lay down cast.
Lay the line out straight 25´ in front of you and keep your rod tip down. Start your cast by peeling the line from the surface by moving your tip to about eye height. Go immediately into the back cast where you fling the line up, and back over your shoulder. Stop your arm just past the vertical. Now we need to pause a little for our line to straighten behind us. Then we cast the line forward and stop our hand hard at eye level, and the line rolls out. Wait with your rod tip high and when the line is straight in the air in front of you follow it down.
I recommend strongly that you seek quality teaching at the outset. It will lay a solid foundation for your cast. I struggled for years mostly on my own. Double hauling the line did not occur to me until after some years. With the methods we now use for teaching fly casting this progress is much shorter and smoother.
The Fly Fishers International has a certification process for casting teachers. There are qualified FFI teachers in every state and then there are local fishing clubs with great casters.
Where you find certified casting instructors.
After laying a solid foundation for your casting stroke you can practice and practice until you get it. This is one of the few sports where you can become better as you get older.