Myth vs. Fact – Soft Golf Balls

Written By: Frank Simonutti, Wilson Golf

Differentiation of golf balls is a difficult proposition. The United States Golf Association rules for equipment set limits on ball initial velocity and overall distance which limits the design of the golf ball. Because all manufacturers design golf balls to approach the USGA limit for initial velocity and overall distance, it is very difficult to make a ball with significant distance advantage that conforms to USGA regulations. As a result, there is a significant level of parity in golf ball performance.

With most golf balls approaching the initial velocity limits defined by the USGA, the challenge becomes how to continually develop golf balls that are longer than the competition, are noticeably different from other golf balls, and stay within the USGA conformance regulations.

Options for golf ball differentiation include:

• Spin rate: Most balls exhibit comparable spin rate as well as distance within the same product category (2-piece Surlyn, 3-piece Surlyn, multi-layer Urethane). A large number players are unable to discern differences in spin rate. Further, for many players a high spin rate (specifically off the Driver) is detrimental as it results in magnification of hooks and slices. For most high handicap golfers, high greenside spin is not discernible, and the benefits of straighter ball flight is a more beneficial performance attribute.
• Dimple pattern differentiation: Golfers generally are not concerned with the dimple pattern, unless the pattern includes non-conventional shapes. Non-conventional shapes have generally not been well received or successful.
• Feel: A performance attribute that can be perceived by golfers of all handicaps.

We have conducted a significant amount of testing of golf balls to determine feel preferences.  Golfers of all ages and handicaps evaluated balls of different compression in blind testing – and test results have shown the following:

• 70+ % of golfers prefer a softer feeling ball compared to a harder feeling ball.
• This percentage is constant regardless of the handicap of the golfer.

There are multiple contributing factors that contribute to the feel of a golf ball, but the largest factor contributing to ball feel is ball compression.

What is Compression?

Compression is a measurement of the deformation of the golf ball under a static load. As the deformation of the ball increases, the compression value decreases. In more basic terms, the lower the compression, the more a ball deforms upon impact with the golf club, and the greater area of the ball that comes into contact with the face of the golf club.

• Compression is calculated based upon the deflection/deformation of the ball under an applied load of 200 lb. Every 0.001” increase in deformation is equivalent to a decrease of one compression point.
• Compression is calculated using the formula:

Compression = 180 – (deformation x 1000)

(A core or ball CAN have a compression of less than zero).

The lower the ball compression, the softer the feel of the ball.

Technology/Construction

To achieve the best overall performance it is necessary to optimize the ball construction to result in the softest feel with the longest distance and spin performance products for all levels of golfer.

To develop a soft feel, low compression 2-piece golf ball it is necessary to design the ball components as follows:

• Golf ball core: To produce a soft core that will produce low compression and high ball velocity, it is necessary to maximize the size of the core and to maximize the level of materials that are reactive components in the rubber core.
  • The largest possible core size is necessary to produce the low compression. The core is the primary contributing factor to producing a low compression ball and the volume of the core should ideally be at least 80-82% of the total ball volume.
  • Maximizing the level of reactive materials in the golf ball core is necessary to maximize the velocity of the core. The lower density of the larger core and the use of heavier non-reactive (inert) fillers allows for a core comprising greater than 96% of reactive material
• Golf ball cover: The cover comprises a Surlyn ionomer composition and needs to be as high modulus (stiff) as possible to provide ball velocity. The limiting factor is that if the cover material is too stiff, the impact of the club will result in excess flex of the cover and result in brittle failure of the cover.
• Dimple Pattern: To optimize flight performance, a dimple pattern needs to be designed to maximize the flight performance of the ball velocity, launch angle and spin rate of the ball that results from the construction. Low compression 2-piece balls will generally have low spin rate and high launch angle compared to harder compression balls, and the dimple profile needs to be designed to maximize carry distance of the golf ball.

The resultant golf ball provides exceptionally long distance performance. The combination of the soft core and stiff ionomer cover also results in a low spin rate which results in reduced sidespin and straighter ball flight.

There are players who prefer a higher spin rate and still prefer the feel of a low compression ball. It is possible, through use of a 3-piece construction, to develop a ball that has low compression/soft feel and achieves a higher level of spin for the players who desire this added performance. The design components for a soft 3-piece ball are:

• Golf ball center: The center of the golf ball is primarily to provide low compression/soft feel and maintain a low driver spin rate for straight flight. To achieve this, a smaller center with a very low compression (significantly softer than the 2-piece core) is required. As the center is not a significant contributor to the velocity of the golf ball it is not necessary to maximize the density of the core.
• Golf ball mantle layer: The inner layer of the 3-piece ball is designed to contribute both to the velocity of the golf ball and the spin of the golf ball. The material used for this inner layer needs to provide as much velocity as possible while also contributing to the low compression of the overall ball. Ideal materials for this inner layer are specialty high-performance terpolymer ionomers designed by DuPont specifically for use in golf balls.
• Golf ball cover: The cover of the golf ball can comprise either Surlyn to produce higher spin than the 2-piece construction, or Urethane to provide maximum spin performance.
  • Surlyn cover: A Surlyn cover for a 3-piece construction needs to be lower modulus than the cover of the 2-piece construction to increase the ball spin but still be stiff enough to provide ball velocity.
  • Urethane cover: A urethane cover needs to be applied to the core mantle combination to produce maximum spin properties. There are two types if polyurethane that can be used as covers for golf balls: cast polyurethane and thermoplastic polyurethane.Either type of urethane can be used, but cast urethane is preferred as it provides better abrasion/scuff resistance and better cut resistance than thermoplastic polyurethane. To achieve acceptable distance performance, the urethane cover needs to be as thin as possible as urethane is a “dead” material and needs to be molded as thin as possible to achieve the maximum possible ball velocity and distance performance.”

The 3-piece ball design performance, for both Surlyn and Urethane covers, is based upon the inner layer (core) having more of an effect on shots with high clubhead velocity (Driver, Fairway Woods, Long Irons) – the high impact on the ball resulting in the core having a significant effect on the ball performance resulting in lower spin rate and straighter flight. As the speed of the club impact decreases, the effect of the core is minimized and the outer two layers become the predominant contributors to the ball performance. This results in higher spin rates (comparatively) as the club head speed decreases – on short iron and wedge shots.

This results in increased greenside performance.

During development of low compression golf balls, we have received feedback questioning the performance of low compression golf balls. In particular, with competitors touting low compression balls for lower swing speed players this becomes more of an issue to try to dispel certain “myths”. The comments we have received the most regarding low compression golf balls are as follows:

• Low compression golf balls are for slow swing speed players.
• Lower compression golf balls are for play in low temperatures.

To dispel these myths, we have tested low compression balls and compared them to higher compression balls.

MYTH: Low compression golf balls are for low swing speed players.

We tested the Coefficient of Restitution of low compression and high compression golf balls at test speeds of 85 mph (125 ft/s), 102 mph (150 ft/s), and 119 mph (175 ft/s). As C.O.R. is a measure of the energy retained during a collision (such as a club/ball collision) this should correlate to the expected ball velocity at different clubhead speeds.

Test results show that there is minimal difference in the slope of the Coefficient of  Restitution between the low compression balls and high compression balls at varying test speeds, indicating no reduction in performance at  high test velocity (corresponding to high clubhead speed) and low test velocity (corresponding to low clubhead speed). This indicates the low compression balls will not have slower ball velocity at higher swing speeds and are not for “low swing speed players”.

MYTH: Low compression golf balls are for play in low temperatures

To disprove this contention, we performed Coefficient of Restitution testing at three different temperatures (30°F, 70°F and 105°F). Testing was performed on low compression balls and results compared to higher compression competitive golf balls.

The results of Coefficient of Restitution testing at various temperatures shows that the low compression balls have C.O.R. that is comparable to or greater than higher compression balls at all temperatures – indicating performance at both low and high temperatures.

Summary

Testing of a significant number of golfers indicates that low compression/soft feel golf balls are preferred by a majority of players regardless of handicap. With the correct design, low compression golf balls can be produced that have distance performance that is as long or longer than higher compression golf balls.

Wilson has been producing low compression golf balls since 1997, and has continued to make advances in reducing ball compression. This led to the introduction of the Wilson Staff Duo™ golf ball in 2012, and has led an industry shift to softer golf balls that provide exceptional distance performance and better feel properties.

Wilson continues to work to advance development of low compression golf balls through application of new, softer materials and improved manufacturing processes. Our goal is to be the low compression, highest performance golf ball in all product categories.