With irons or any shot with the ball on the ground:
According to D Plane information, in order for the ball to fly straight, the normal to the clubface(the 3d location of the where the clubface is pointing) and the club path must point at the target at the hit. It is also a requirement that the ball is hit absolutely solid(right in line with the CoG). This location is basically a point and any mistake left or right will alter the shape of the club during the hit.
I mentioned in a previous blog that I am having some research done on this topic but hopefully it confirms my thoughts and trackman’s claims.
Back to the topic. Because the ball is hit with a downward angle of attack on a crisply struck iron shot, the club is still traveling downward and outward after hitting the ball until it reaches low point. Because the club travels to the right after the hit the path of the club(relative to the ball) is inside out. The impact path is right of the low point swing path.
This Picture will help you picture this is it doesn’t make sense.
It is for this reason that you must either aim or swing a little left for the ball to actually fly straight. Even though the club is swinging left, relative to the ball the club path can now point exactly at the target.
Keeping the club constant, the more down angle you have in your strike the more to the right the clubs actual path becomes. Thus, you will have to aim more left. The amount of left you aim depends on your angle of attack and what club you are using.
There’s a relationship between the shape of the swing plane and the amount the club is moving out after the strike. As the swing plane get’s more vertical the amount of out becomes less all while the amount of down is increasing. Ferris wheel would have all down and no out.
As the swing plane get’s flatter, the amount of out is increasing while the amount of down is less. A merry-go-round would have all out and no down.
Depending on a persons impact angles, it will depend on whether or not they aim/swing more left with shorter clubs or longer clubs. If someone hit all clubs with the same angle of attack, they would have to aim/swing more left with a 3 iron vs a wedge.
If the player’s angle of attack get less by more than 1 degree from wedge to 3 iron than that player would aim/swing more left with the wedge.
Most player’s will fit into this second category where they aim/swing more left with shorter irons than longer ones.