Knots in your leader comes from tailing loops. Which means that you are not stopping the rod on the way back, and then you start to go forward before the line had the chance to extend all the way behind you. The sound of cracking a whip come from the same thing when you accelerate the line going forward. That will snap off flies all day. You have to think about the movement, and when you bring the rod back you have to stop the rod and give the line the chance to basically unfurl all the way before you bring the rod forward. And with the size rod you are using, you are throwing some big flies so you will feel a slight tug back when the line is completely unfurled, and that is the signal to then take the rod forward for your cast. Think of a clock when you are casting back and forth. The rod in your hand should only go back to two o'clock and then forward to ten o'clock. So the rod straight up in the air is at twelve o'clock, behind you two o'clock, and then forward to ten o'clock. Your casting should be from your elbow to your wrist, with slight flicks of the wrist going back and forward. To get distance it's simple, remember, leave it high, watch it fly, leave it low, it won't go, meaning, if you leave you rod tip high when going forward, you fly will travel farther out. From the high point, the lower you bring your fly rod tip, the shorter the distance.
