At PRGR, a studio equipped with computer-developed swing analysis systems such as Science Fit has been used to accumulate data from a large number of amateur golfers who have come to the studio for evaluation. Akira Yashiro of the Sports Division developed the plan for the GN502 series based on analysis of this accumulated data.

“First, we focused attention on grip speed. In up to 70% of the data, the golfers are what can be called body turn type golfers. These golfers have an early release type swing where kicking occurs according to how fast the club is cocked in the downswing. Also, from the analysis data of the direction of the face at impact, we saw that the face was open with these golfers. This causes a right side spin on the ball, which results in slicing. This reduces distance and destabilizes the ball direction. We thought about what kind of club we needed to design to allow this type of golfer to be able to achieve a square impact. In addition to the shape and features, we also included consideration of the visual effect of the clubs when we started development.”

Tour pros and highly-skilled amateurs possess the skill needed to achieve a square impact with the ball. These players excel at gripping the ball. Put in another way, these players could simply say that they grip the ball at impact and turn the head of the club. These actions clearly show the intent of the golfers. And, with clubs also, there is a strong desire for ease of use with clubs in line with these intentions. One example is with the centre of gravity distance for clubs. Turning the head and gripping the ball feels easier with models in which the distance from the shaft to the centre of gravity is short.

So how does this affect the 70% of golfers identified with the accumulated data? This type of golfer lacks the skill to achieve a square impact just through their own effort. For this reason, Mr. Yashiro started from the idea of including features that would allow these golfers to overcome their skill deficiencies. This was one of the major development themes common to the driver, fairway woods, and irons of the GN502 series.

Instead of making it easier to grip the ball, make it more likely that the ball will be gripped. Instead of making a club that is easy to turn, make a club that turns easily.

The centre of gravity distance of the GN502 driver is designed to be long. The toe side, in comparison with the previously manufactured T3 502 Silver driver, has a greater volume. Moreover, the centre of gravity angle is 30 degrees. These specifications can be called hybrid features which, for all golfers with an early release type swing, create the maximum amount of centrifugal force while at the same time making it easier for the head to turn naturally in that type of swing and allow for a square impact to be achieved.

Mr. Yashiro, holding the completed GN502 driver in his hands, stated the following with an air of gratification: “This driver allows you to overcome skill deficiencies and grip the ball squarely. At the same time, with early release type swings that have a large arc from the downswing, it lets you aim for improved distance by allowing for smooth acceleration. Even with a deep centre of gravity, instead of letting you hook the ball, the intention of the design was to improve features that allow you to hit extremely straight shots. The ease of use we aimed for was targeted at golfers who worry about slicing or golfers who hit the ball with an open club face and experience loss of power, and the result of those efforts is this product.”

For the previously described 70% of golfers, what is their image of the 3 wood? In the survey, these golfers overwhelmingly answered that the 3 wood is a difficult club. Specifically, many golfers answered that it is difficult to lift the ball, they can’t hit the ball cleanly, and they often have bad shots with the 3 wood.

For this reason, Akira Yashiro based development of the GN502 HIT on the idea of making it easy to lift the ball, making it easier to hit the ball cleanly, and eliminating the image of the 3W as a difficult club.

“We thought about what shape would visually give golfers a sense of stability. Also, we thought about what kind of head would make it easy to lift the ball and, at the same time, make it possible to hit extremely straight shots like with a driver. We used a shallow head with maraging steel in the face. We also made the crown thin and lightweight (12 g lighter in comparison with conventional crown), and we took that weight and distributed it to the sole and the rear area. We mounted heavy tungsten in the sole. By doing these things, we were able to set the centre of gravity height at 23 mm.”

With the shallow head and low, deep centre of gravity design it is consistently easy to lift the ball, the ball is gripped, and the effect of maraging steel provides shots with high initial velocity and a high degree of straightness.

“The short woods are designed so that the ball is gripped but it doesn’t catch.”

If the swing characteristics of 70% of golfers are applied to irons, these golfers will tend to have a swing path that sweeps the ball rather than hits down on the ball. Regarding this, Mr. Yashiro stated, “With this being the case, we aimed to create irons where, even with this swing path, a square impact could be achieved, the ball could be easily lifted, and sufficient flight distance could be achieved.”

The centre of a ball is at a height of about 21 mm. If the head centre of gravity for irons can be made slightly lower than this height, the trajectory will be high even with a sweep shot and, moreover, shots will have an appropriate amount of spin. The resulting design was a structure in which plastic is inserted in the head upper part and below the top blade (3-9 iron). This created a 5 g margin with weight. By distributing this weight to the sole portion and mounting maraging steel in the face as with the fairway woods, a low and deep centre of gravity was achieved. The soft feel at impact is also one more effect of maraging steel. Even with a deep centre of gravity, care was taken during design so that the rear part of the sole that sticks out cannot be seen when addressing the ball (a surprisingly large number of golfers don’t like this). The semi-large size head was also designed with aesthetic appeal in mind.

There is an important key point when it comes to irons. This key point is that it should be possible to hit all irons with the same rhythm and timing. Mr. Yashiro stated the following: “All of the irons, while maintaining a centre of gravity height of 20 mm, are designed so that there is a centre of gravity (distance) flow in which the internal cavity is uneven. This was done so that, with all the irons, the head returns and the ball is gripped as with long irons. The short irons are designed so that even though the grip is good the ball does not catch.”

The driver, fairway woods, and irons of the GN502 series were all planned and developed with the previously mentioned 70% of golfers in mind.

Next, we'll hear about how shafts were developed to further utilize the characteristics of these heads to create synergistic effects. (Continued)