Drop is used to refer the angle and speed of the drop of a subsurface fly.
Having a steeper drop angle means subsurface flies are drifting in the feeding zone longer which allows for more takes. There are several ways to increase the drop angle:
- Weight -- the most direct way to increase "drop"
- Target -- Casting your flies into slower water will allow them to drop. Pro tip: We all have an intuitive tendencey to pull back when the flies hit the water. If you can push forward instead the flies will be "allowed" to drop.
- Drift technique -- line mending, suspension indicators; anything that will prevent the line from pulling up the flies. Pro tip: When Euro nymphing (especially at a distance or across fast water) underline your rod so that the lighter line has less drag
- Tippet Material -- Fluoro tippet has a higher specific gravity than water and therefore drops more easily than mono.
- Tippet Diamter -- Thinner tippet slices through the water more easily (quickly) than thicker tippet. Small changes (changing to 6X from 5X) can have remarkable effect on drop.