DOUBLE HAULING
You asked about a double haul---there are several things that need to be accomplished to get the most from a haul. Unfortunately, most fly fishermen only use one.
I'll talk about the forward cast--but of course it applies to either back or forward cast. When you are sweeping the rod forward it bends some. If you haul you add two more factors---you increase the line's speed and you create an even deeper bend in the rod---which means storing more energy in the rod.
This is what most people accomplish when they haul--but they neglect to add the other factors that will improve their haul.
It is important to understand that the hauling hand should replicate what the rod is doing. Re read this last sentence --it is the key to improved hauling.
A basic casting stroke--with any type of fishing rod is a relatively long acceleration of the rod, followed by a rapid speed up and stop. The only difference between fly casting and casting other gear is that in fly casting we UNROLL the line to the target--with other tackle the lure drags the line to the target after the speed up and stop.
When the angler accelerates the rod forward it stores in the rod energy and accelerates the line. The haul does the same to the line and rod. Ideally you should be ACCELERATING THE LINE HAND AND THE ROD TOGETHER. This rapidly accelerates the line and and bends the rod deeper--increasing the stored energy. The faster the rod is accelerated the faster the line travels--and if the haul speed is accelerated, additional line speed occurs.
If you go back to a basic rod stroke, there are two parts, the relatively long acceleration--followed by a brief speed up and stop. Forget the haul for the moment. If you accelerate a rod forward and release the line without a speed up and stop--the line will travel only a short distance in front of the caster. If you make another forward cast--but add the speed up and stop the line takes off. AFTER THE ACCELERATED FORWARD STROKE IT IS THE SPEED UP AND THE STOP THAT UNROLLS THE LINE TO THE TARGET.
The stop is vital to obtaining a good back or forward cast. What almost all double haulers do is they stop the rod hand to direct the fly at the target---BUT KEEP ON HAULING. Remember I said that you need to replicate the rod stroke with the line hand. If you continue to haul after the rod hand stops--the rod tip does NOT stop abruptly--and that is why many good casters have deep dip or sag in their forward cast. To improve your haul you should accelerate the rod and line hand together--and both hand speed up and stop together.
The major function of the rod hand in a casting stroke is to accelerate the line, form a tight loop and stop the rod in the target's direction. THE MAJOR FUNCTION OF A HAUL IS TO REPLICATE THIS-----BUT---WHEN YOU NEED MORE DISTANCE OR LINE SPEED IT SHOULD NOT BE ATTEMPTED WITH THE ROD HAND--this is what causes that lousy final cast when someone tries to throw a bit farther than the can comfortably.
INSTEAD, THE ROD HAND SHOULD CONTROL THE ACCELERATION OF THE ROD, FORM A GOOD LOOP AND STOP THE ROD IN THE TARGET'S DIRECTION. HERE IS WHAT I BELIEVE IS THE LEAST UNDERSTOOD PART OF THE HAUL; WHEN YOU NEED EXTRA DISTANCE OR SPEED____INCREASE THE SPEED OF THE HAUL___NEVER ATTEMPT TO DO IT WITH ROD HAND.
Try this exercise-----alternate your regular haul speed with one where the line hand moves at a much faster rate during the haul. You will see loops tighten and a rapid increase in line speed. The tendency when doing this exercise is to over power the rod hand spoiling the cast. When learning to increase hauling speed I have men hold the rod with only the thumb and first two fingers. That way they can't over power the rod. With women I usually suggest holding the rod with one more finger.
I hope that is not too long and that you can make some sense of this.
All the Best, Lefty