Golf is considered a difficult game because of the considerable uncertainty about how far and in what direction a golf ball will fly. The cause of this lies in the fact that the ball is forcibly struck by the golf club, which comprises, relatively heavy club-head affixed at one end of a long shaft so that the club-head juts out. In a golf swing, the body forms the axis for a turning action of an object having a length formed by the golf club linked to the arms. Of most important at the moment of impact is the angle formed by the golf club and the straight line formed by the left arm and the left-hand grip portion where the left arm joins the golf club. While describing the body as an axis of rotation, the human body is not a fixed axis which is rotated by a force applied from without, but is instead a movable axis possessing sentient faculties which is autonomously moved in delicate curves for alignment with the golf ball. Similarly, the arm does not form the type of simple swing plane such as is applied by a swing machine. That is, functionally the position of the gold ball is visually ascertained and mental calculations are then undertaken by the golfer to form a mental picture of the swing that is a composite of the club-shaft swing plane and the distance. At this time it is the club-shaft which forms the mental picture of the swing plane. It is considered that the ball can be hit farthest and with accuracy when the tip of the swing plane described by the club-shaft coincides with the center of gravity of the club-head, or the sweet spot. However, notwithstanding that there is always a slight discrepancy between the plane of the club-shaft swing path and the path of the center of gravity of the club-head because of the shape of the golf club, because the swing by a human being is based on his image of the swing path described by the club-shaft, it is not possible to strike the golf ball when the tip of the swing plane coincides with the center of gravity of the club-head.
That is, the club-head is jutted out to maintain a lie (the inclination of the sole of the club-head relative to the club-shaft) and as such it is difficult to have the point of impact, which is at the tip of the swing plane that is described by the club-shaft, coincide with the sweet spot (center of gravity) of the club-head. It is the whippiness or flex of the club-shaft in the course of the swing that removes the slight discrepancy between the plane of the club-shaft path and the path of the center of gravity of the club-head. The whip of the club-shaft during the swing is as shown in FIG. 5. Here, as the club-shaft 14 moves from the top of the backswing A to the beginning of the downswing B, the club-shaft 14, being lighter than the club-head 16, is ahead of the club-head 16 as the club-shaft 16 flexes toward the backswing portion. At position C, the acceleration of the heavier club-head 16 is starting to bring it ahead, and the club-shaft 14 is starting to whip toward the forward part of the swing. In this flexed state, the club-head 16 is turned as it moves through position E to position F. In the transition through position E and F, the club-shaft 14 and the club-head 16 are rolled through 90 degrees, bringing the club-head face into square alignment with the golf ball 11. It is the way the club-shaft whips during this rolling of the club-head that has the most influence on the impact timing of the swing. FIG. 6 is a plane view of the relationship between the center of gravity of the club-head and the whip of the club-shaft during the part of the swing plane in which club-head is rolled to produce optimum impact. FIG. 6B shows the ideal whip of the club-shaft to enable the ball to be struck with the optimum impact. That is, the grip 12, the club-shaft 14 and the center of gravity 18 form a straight line along a line of extension 20 of the club-shaft 14 when the club-shaft 14 is in a non-flexed state, with the center of gravity 18 at the tip of the swing plane described by the club-shaft 14 and wherein even if the center of gravity 18 of the club-head 16 is rotated by b 90 degrees, it does not deviate from the swing plane. (In FIG. 6B, for illustrative convenience, the club-shaft 14 is shown as whipping below the line of extension 20, but the actual whip is a composite of the whip in the horizontal direction relative to the plane of the swing path, and the vertical whip, and is a diagonally downward flex relative to the plane of the swing path.) In this state the impact will be optimum. This optimum impact cannot be achieved if the amount of whip either exceeds or falls short of this ideal whippiness. With reference to FIG. 7 which is a plane view of the relationship between the center of gravity of the club-head and a club-shaft exhibiting excessive whip as it approaches the part of the swing plane in which the club-head is rolled, if the club-shaft 14 whips too much, as shown in FIG. 7B, the toe portion 22 of the club-head 16 will lie on the line of extension 20 extending from the grip 12 down along the club-shaft 14; striking the ball with this portion will produce a hooked shot. FIG. 8 is a plane view of the relationship between the center of gravity of the club-head and a club-shaft exhibiting insufficient whip as it approaches the part of the swing plane in which the club-head is rolled. As shown in FIG. 8B, here, the heel portion 24 of the club-head 16 lies on the line of extension 20 of the grip 12 and club-shaft 14; striking the ball with this portion will have a gear-wheel effect that will result in a sliced shot.
In view of the foregoing, in order to achieve optimum impact, the whip shown in FIG. 6B is necessary, with the sweet spot located on the line of extension of the club-shaft. In order to have the club-shaft whipping as shown in FIG. 6B at the moment of impact, it must be securely fixed to form an angle of around 155 degrees between the straight left arm and the club-shaft. This is also the ideal angle to maintain because when held straight the human wrist joint is prone to impact in the direction in which the ball is sent. With the club-shaft brought into impact in the state in which the grip is maintained at this angle, at the stage of impact the ideal whip such as is shown in FIG. 6B is generated by the momentum stored as the inertial moment of the club-head in its descent in the downswing. The effect of this whip in the follow-through to the swing along the line of flight is to lift the ball and increase the distance of its flight.
It is therefore necessary to limit precisely the whippiness of the club-shaft. Optimum impact cannot be achieved if there is too much whip or if there is too little. Expressed another way, what is difficult golf is the adjustment by the golfer to an optimum whip for the swing so that the club-shaft does not whip excessively or insufficiently; this can also be referred to as the technique of golf.
With conventional golf clubs, in order to impart the ideal whip to the club-shaft and have the sweet spot at the moment of impact located on a straight line extending from the grip, it has been necessary to strike an optimum balance among four conditions: the speed of the downward swing, the weight of the club-head, the degree of elasticity, and the lie angle. However, because the weight of the club-head, the degree of elasticity, and the lie angle have already been fixed during the manufacture of the golf club, it has been necessary for the golfer to produce the ideal whip by regulating the speed of his swing. It is not, however, easy to consistently produce this ideal whip of the club-shaft. Even with respect to those persons who are considered to have adequately mastered the technique of producing it, there still remain elements of uncertainty that can cause variation in the degree of imparted whip, such as physical condition, atmospheric temperature and the like. In fact, ordinary golfers can only be described as lucky if they, unable to find a golf club which matches their strength, happen to purchase a club which results in the requisite balance being achieved between their swing speed and the weight of the club-head, the degree of elasticity, and the lie angle for producing the ideal club-shaft whip. Instead, the majority are obliged to use unsuitable clubs.