Keeping flies in the strike zone is not enough; they need to look like natural insects. An effective nymphing system requires drag-free drifts. This means controlling the speed of the nymphs in any type of water, even in fast, complicated waters.
It is important to consider that trout are as sensitive to underwater drag as they are to surface drag. Getting dead drifts is as important to nymph fishing as it is to dry fly-fishing, and the path and speed need to be controlled in order to not spoil the presentation. The drift speed is driven by the current at the depth of the insect. Insects have a natural movement, drifting freely. That is what is called a dead drift.
A river’s water column has an important characteristic that the angler needs to understand and master. There is a difference in speed between surface current and the current close to the river bottom. The fastest-moving water is located just below the surface, and it gradually decreases the closer you get to the bottom. Very close to the bottom, the water speed is almost zero because of friction and the hydraulic cushion created by structure. The different speed layers form a parabolic shape that is copied by the tippet under the water.
This difference in current speed creates a very important complication in traditional nymphing techniques. Nymphs must drift at the speed of the current at the nymph’s depth, but they are attached to a floating indicator, which is affected by faster currents. The speed difference in the water column creates drag.
The currents push the tippet and any floating devices downstream like a sailboat driven by the wind. Wind is blowing the sail, creating forces that pull the hull. The wind speed is higher than the sailboat’s speed, and the bigger the sail, the faster the speed of the boat. The floating indicators suffer a similar fate and are pushed by the currents.
This push force is transmitted to the flies through the tippet, affecting the speed and the path of the flies, which creates drag. This drag pulls the flies and lifts them from the bottom. Also, since the indicator is affected by currents that are faster than the current speed at the nymph’s depth, the nymphs are accelerated. Both effects ruin the presentation and make the flies drift in an unnatural way. This negative acceleration and lift from the bottom is worse with fast currents, since flies are accelerated to the speed of the fastest current at the surface.
Lift and acceleration forces spoil the dead drift of the flies. Therefore, an effective nymphing system requires a disconnection of the speed of the nymphs from the current speed at the surface. This requirement forces you to not have any part of the ring floating on the water surface.
The goal is to prevent the flies from being pulled downstream by anything in the rig moving close to the water’s surface speed. To achieve this goal, there is no floating indicator, and even the floating line can be eliminated, using a very long leader instead. By using monofilament as a substitute for fly line, the rig can be cast at remarkable distances and held out of the water for a good drag-free drift.
Drag-free drifts are attained by putting the right tension on the leader. It is neither tight nor slack—just a gentle bow keeping contact and control while permitting the flies to drift freely. Dead-drift attainment is one of the keys to success in contact nymphing.
Compared with indicator nymphing, contact nymphing has these advantages related to the deadness of the drifts:
Requires no mending, because the leader is off the water at all times, allowing you to fish the most complicated waters.
Drag is minimized because there isn’t any floating element. There is certainly contact with the flies, but it’s not so tight that the fisherman interferes with the presentation of the fly in dead drift.
