All I know is if I hit a ball with front or back it does not travel off the path, if use any other English it will travel off line and then back on.With an off-center hit, while the tip is in contact with the CB, the CB starts to move forward and turn. The ball turn pushes the tip away sideways causing the end mass of the shaft to move. Mass doesn’t like to move, so it pushes back during contact (because for every action, there is an equal and opposite reaction). That’s why the CB deflects (squirts) off line.
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Backhand english (BHE) and front-hand english (FHE) are aim-and-pivot methods used to adjust one’s aim for squirt and swerve (AKA “cue ball deflection”).
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@jasonlaus
you have to get squirt when you hit the cue ball off vertical axis
bhe and fhe only help to get the cue ball to go where you want it to with a vertical axis hit
for example
if right hand english would make the cue ball miss the target by 2 inches because of squirt
bhe/fhe help get you to aim that 2 inch difference so you hit the target
the above is from dr dave with some parts bolded and larger font for emphasis by me
I have demonstrated this to quite a few people