lag
shot Dr.
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What's the best way to hit a lag shot?
Obviously, the goal is to leave the CB as close to the head rail as possible as often as possible. For the best and most consistent speed control, it is better to hit above center for immediate roll. If you hit at or below center, you need to judge the speed loss due to drag on the cloth, and this will vary with cloth and ball conditions.
When the CB rebound off the rail, it will lose speed due to rail inefficiency. Also, roll into the rail typically converts to stun on rebound (e.g., see HSV 7.16), which slows the ball (due to skidding) even more. That's why it is generally better to try to hit the head rail with your lag shot. This will generally result in the best average lag results (i.e., proximity to the rail). If you are a little short, you will be a little short. If you are a little long, the CB will lose speed off the rebound, and end up very close to the rail ... closer than if you are a little short.
from Bob_Jewett:
There is a certain
height to hit the cue ball that makes it insensitive to how high you hit it. That
is about 60% of the height of the cue ball. Suppose you hit with some draw. If
you hit a little lower, you will first have more draw on the ball which will slow
it down, and second, you will have less initial speed in the cue ball, due to
the more off-center hit. The conclusion is that it is very bad to hit a lag with
draw unless you can hit very, very consistently at the height you want.
On the other hand, if you hit somewhat above center, the cue ball starts out with some forward roll. If you hit higher, it will have more forward roll so there won't be as much slowing as it acquires full roll, but it will not start as fast because you are hitting the ball more off-center. These two opposite effects will cancel exactly at a certain height and that is the height you should hit the cue ball. The actual height depends on the weight of the stick, as I recall, and the springiness of the tip, but for common values, you want to hit about 1/4-inch above center or at 60% of the height of the ball.
You would start with smooth rolling by hitting at 70% of the height of the ball, but that's not best for this purpose because a little higher or lower will change the total distance traveled more.