Odds 'n' Sods of Information and Opinion

Full sinker control

Full sinker control:


We're familiar with mending sinktip systems to control depth and speed, Full sinkers obviously have limited opportunity for mending, so it's understandable that those who rely on mending sinktip systems to get the fly down, assume that the lack of mending a full sinker means lack of control. Not true. Mending can be accomplished via air mends, reach mends, or a water mend just as the line lands. Once the line is in the water, presentation and depth control are maintained through rod tip position, the distance cast, casting angle and line tension.

Sinktip users might think that the lack of mending capability of full sinkers impairs control. However, this overlooks one important consideration. With a sinktip system, the angler is trying to get the fly into the slow, bottom currents and keep it there while the floating belly remains stuck in the fast, top currents. Those fast, top currents are always dragging the floater belly and working at pulling the fly back up. The use of T-14 and heavy, weighted flies is a response to this problem as the density of the T-14 and the weight of the fly counters the drag of the current on the floater belly. It's a straightforward approach to overcome the problem of a lifting fly induced by current drag on the floater belly, and it works very well. It does a great job of keeping the fly in the zone, but such an approach isn't needed for a full sinker.

Full sinkers don't have this problem simply because they quickly get below the top, fast currents and the entire line ends up in the slower, bottom currents. There's no need to mend, mend, mend or apply gobs of weight on the fly, as there's no dragging floater belly trying to pull the fly back up. More importantly, there's no need to mend to slow the presentation down as the entire line is in the slower currents, so the fly is moving slowly without the need of a lot of angler intervention.

Current Speeds by Depth (1)
This diagram illustrates the difference in current speeds produced by a rough bottom contour. The greater the bottom friction from the roughness, the greater the disparity between top and bottom speeds. Full sink lines spend most of their time in the mid to bottom currents so they tend to run straighter. Since most of the line is within a band of current running at more or less the same speed, various sections of the line are not being pulled against the others. This differential in current speeds is the main reason why sinktips tend to develop a big curve or sag in the belly of the floater line as they swing around. The floater belly is stuck in the top, fast currents while the sinktip is dragging behind in the slower, lower currents. Adding a weighted, high drag fly makes this differential and the resulting belly sag even worse.

The full sinker also helps us to keep better contact with the fly. Without the droop of the sinktip and the current induced, downstream belly sag, the angler using a full sinking line, has an almost straight-line contact with the fly. We feel everything going on at the end of it. The slower bottom currents not only apply less force on the line, full sinkers also have less hydrodynamic drag as they are thinner than floater bellies. Consequently even without any mending, there is much less current induced downstream belly sag in a full sinking line, and even less in a short full sinking shooting head.