This is a tackle tip that I haven't run for sometime, but this month's Fly of the Month reminded me so here it is.
Big flies like the Daddy Longlegs can cause a phenomenon called "helicoptering" when the fly twists in the sir, twisting the leader and creating a sort of open -spring effect. You also get problems if the leader material retains "memory" from its packing spool, either way the effects are the same, a problem that usually affects fly fishing rather more than other methods, - the Pig's Tail leader. You will have seen this, when there is so much memory in the leader material that it coils across the surface of the water. It won't sink, it stands out a mile and no self-respecting trout will come within 30 feet of it! We talk a lot about how good fly lines are at resisting memory when on the reel, but the same problem applies to leader material that has been stored on a spool too. So what is the solution?
One way to deal with this is to use a line straightener - usually made of rubber, you draw the line through the device. This action stretches the line slightly, but also straightens it. Of course, you may not have such an item in your bag (make a note for Christmas), and I am indebted to Kevin Struthers of Whitecross for the answer. Wet your thumb, then draw the line between your thumb and the cork handle of your fishing rod - works a treat, but always work towards the fly. Watch the end of your line as you do this, either with a line straightener or using the thumb and handle method, and you'll see the line untwist as you pull it through.