The following Figures 6 and 7 show the affects of centrifugal force on the golf club. Centrifugal force is that force that you experience when you put a weight on the end of a string and whirl it around. When the weight gets to a certain speed it will pull the string straight and stay in a circle about your hand. the faster the speed gets the higher the force trying to pull the string from your hand. In the case of the golf club the head is the weight on the end of the shaft/string. In Figure 6 the centrifugal force is causing the shaft to deflect into a toe down or a shaft droop direction. Also shown in figure 6 are two clubs the top one with a high flex point and the lower one with a lower flex point.
Figure 6 Figure 7
The maximum deflection from the centrifugal force will align the grip end of the club with the Center of Gravity (C.G.) of the head. When you turn the club around, from back swing to down swing, you will load the shaft in a toe up direction. This toe up shaft deflection will snap back during the down swing and will add positively or negatively to the toe down position of the head at impact dependent on when in the down swing that toe up load is released. Both of these deflections depend highly on the stiffness of the shaft. Therefore when being fitted for the lie angle of your clubs the testing must be done with the club you will play with. This toe up toe down affect will affect all of your club but will have less affect as the shaft gets stiffer. In Figure 7 we show a face up club head rotation caused by the centrifugal force. Again the maximum deflection induced by the centrifugal force will not be greater then when the head’s C.G. is aligned with the grip end of the club. The flex point of the shaft as well as the stiffness of the shaft will have an affect on this deflection. This deflection is much more predominate in wood heads then in iron heads because of the G.G. location with respect to the shaft. This affect is why the club manufacturers have placed more weight back in the head to help the player get more effective loft. The fallacy with this is that the average player that can use the greater loft does not have the club head speed to produce the affect.
Figure 8 Figure 9
If we closely look at many pictures of players swinging a driver we can see that the forward shaft deflection has the head well ahead of the position where the grip end of the shaft is in line with the head’s C.G. as in Figure 8 and 9. This condition is caused by the combination of centrifugal force and the shaft being too stiff and being released too early for the player’s swing timing. This not only leads to inconsistencies in the players drives but a loss in efficiency of ball impact. Not only has the club loss some effective club head speed by being so far ahead of the shaft it has also built up a load in the shaft that wants to pull the head away from the ball if it should lose club head speed. At Ball impact the club head does lose some speed as it compresses the ball and transfers its energy into the ball. Because the shaft is trying to pull the head away from the ball at this time the efficiency of this energy transfer is reduced and results in the loss of distance.