Thin-face clubhead designs are winning popularity on and off the Tour. But do clubmakers have all the answer to this new, hot technology?

The golf equipment probably couldn't exist if some "hot-technology" did not come along every year or so to stir up golfers' interest. This year, thin-face metal wood designs are the latest "hot" technology and it's no surprise that golf companies are positioning themselves to take full advantage of that.

In short, If clubmakers believe that they are seeing a lot of thin-face clubhead designs in the industry today, they ain't seen nothin' yet. Clubhead production foundries around the world report that a large number of new thin-face drivers, woods and even irons are being tooled in preparation for release later this year and in 2001. As a result, clubmakers need to know how to inform their customers about the facts and fallacies if thin-face clubheads if they ever hope to deliver the best product for each customer's individual game.

Do clubheads with thinner faces hit the balls farther?
With the marketing hype that surrounds thin-face clubhead designs' most golfers will be misled to believe that any thin-faced club made is going to hit the ball farther. This assumption is absolutely false and represents the first point that clubmakers should explain to their customers.

First of all' a thin face can generate a small increase in ball velocity and distance if the face thickness is tailored expressly to the type of metal, the size, loft, bulge and roll of the face and the swing speed of the golfer, In short, just because a clubhead is said to have a thin face, there is no guarantee that the face thickness of that clubhead will make any difference in performance for the golfer.

Are drivers the only club which can successfully be made into thin-face clubs?
Irons are not good candidates at all for a thin-face design, but designs for fairway woods can take advantage of the thin-face technology almost as well as drivers.

Primarily, the reason for the difference involves the club's loft and the area of the clubface that can be made more flexible. For example, imagine the difference between a large and a small trampoline. With the exact same springs and the same person jumping, the large trampoline will deflect more and generate more 'spring'. With same concept applied to golf technology, a larger unsupported face area of the clubhead has more potential to deflect the face inward and improve the energy transfer to the ball.

Taking this example a step further, imagine jumping on the large trampoline while it is positioned at angle. This is similar to what happens when the ball impacts a less-lofted clubhead compared to one with more loft as in the case of irons. The more the force of deflection is angled to the face surface, the less that surface can deflect. Hence, the smaller the face area for flexing and the more loft of that face, the less the face deflection can be. And the less the face deflection, the less the game enhancement effect of the thin face can be for the golfer.

Remember, this is not simply a matter of how large the entire face area may be, but how much of the face area can be flexed inward.

What is the difference between a thin-face steel clubhead and a thin-face head made from another metal?
How much a clubface flexes inward without breaking is certainly a product of its face area, loft, bulge, roll and thickness, but it is all ultimately controlled by the mechanical properties of the metal used in its construction. The best materials for thin face or rather, spring-face construction are the ones that have the highest strength and the best elastic modulus together at the same time.

Highest strength alone does not make a good material for a high performance thin-face clubhead, and a materials needs to have decent strength along with elasticity to perform. While high-strength steels have a little better elasticity than other steels, it appear that the higher strength beta grade titanium alloys offer even more because titanium has twice the elastic property of steel. Even though some steel alloys are as much as 50 percent stronger than the strongest beta titanium alloys, the fact that the titanium has twice the elasticity as any steel is the factor which eventually swings the tide of thin-face back to titanium in 2001. Because of this elasticity difference it is possible to make a titanium driver with a thicker face than a steel drivers and which flexes inward more than a much thinner steel face. And the amount of face flexing is the key to how much better the clubhead will perform.

What is thin for a clubface?
Face thinness depends on many factors, not the least of which is the strength of the material and the face area. Before information about thin-face clubhead design surfaced, virtually all 17-4 grade stainless steel metal woods were made with a 3mm thick face. This was because foundries and golf companies discovered through years of experience that a 3mm-thick face on the stainless drivers and fairway woods made in the 1980s and early 1990s did not break when used by even high-swing speed golfers.

When titanium woods appeared in the mid-1990s, the vast majority were made with a 3mm-thick face on traditionally sized woods and 3.2mm face thickness on larger wood faces. Today, clubmakers cannot think of the thinner face providing better performance. Face thickness has to be chosen carefully for the area, loft, bulge and roll, the material strength in the face construction, and the golfer's swing speed (how much stress will be applied to the face). It might make a customer think that one driver with a 2.2mm-thin face will hit the ball farther than another with a 2.6mm face thickness, but this might not be the case. If the 2.6m-face clubhead has 50mm tall face made from a higher strength beta grade titanium, it will flex inward more than 2.2mm face made from any high strength steel.

How does a thin face generate more distance?
In the collision of the clubhead with golf ball, no matter the player and how good the impact, there is always a loss of energy. This is because the ball squashes a little bit against the clubhead, as well as because the face itself deflects inward in response to hitting the ball. So, no matter what, there is a loss of energy in any golf club to ball impact.

Between the clubhead and ball, the vast majority of the energy loss comes for the ball because it is compressed and squashed much more to its size and mass than is the clubhead. High speed photography shows that a two-piece ball squashed up to 20 percent of its diameter while a wound-center ball flattens as much as 30 percent. That 'squashing' is a loss of energy. If the ball can be designed to deform less because the clubface deflects more, the result will be an overall reduction in the loss of energy at impact.

Hence, the goal of thin-face clubhead design is to increase the face deflection to the point that it reduces the amount of ball squashing. If that happens without causing the face to break or permanently bend inward, the amount of energy retained in the impact will be greater and with it, the velocity of the ball off the face will increase. This in turn translates into greater distance.

How do designers know how thin to make a clubface?
Most designers do not realize that for thin-face technology to work, the face thickness has to be tailored to the swing speed of the golfer. In other words, the clubface for a 75mph swing has to be thinner than it is for a 90mph golfer and thicker yet for a 110mph player. This is because the higher the swing, the greater the amount of force that is applied to the face at impact.

For a slow swinger to gain the same benefit as a high swing speed golfer, the face of both drivers should flex inward by the same amount. When two golfers of different swing speeds hit a club with the same face thickness, it is impossible for both swings to cause the face flex inward the same amount. The clubface that flexes inward the most gains the most in terms of reducing the loss energy.

Therefore, if a company makes a clubhead with only one face thickness, that the club benefits the high swing speed player far more than the average-to-slow swing speed player.

Can a thin-face driver provide more distance?
As the thin-face boom gains momentum, there will be wild reports of perceived distance increases from thin-face clubheads, most notably drivers. When reacting to such reports, clubmakers must remember that face thickness is not the only factor which has an effect on distance.

Therefore, if a golfer makes a switch to a thin-face driver that also has a different loft, length and other specifications from his or her previous club, there is a distinct possibility that the club specs other than the face are contributing to the overall performance improvement.

But with all things being equal between a thick-face driver and driver with its thinner face correctly matched to the golfer's swing speed, the real improvement in carry distance will not be greater than 10 yards. The primary reason for this is because there is a limit to the head's Coefficient of Restitution (COR), the scientific phenomenon that describes the collision's efficiency between the clubhead and the ball.

The COR is a numerical rating of the elastic nature of a collision between two objects. A perfectly elastic collision between two objects has a COR value of 1.0, however, that COR value is impossible to achieve because clubheads and balls are so different in their weight and material. The old, traditional driver with 3mm-thick faces have a COR in the range of 0.77 while the USGA has applied a limit of 0.83 on drivers today.

Doing the math, a driver with a perfect 1.0 COR, would have a distance increase over driver with a 0.77 COR of about 30 yards. But because the theoretical limit is 0.90 COR, that places the distance increases at about 17 yards. Drop that down to the real 0.85 for the highest COR of a club known today and the maximum distance increase for golfer would be around 10 yards. In real terms, the distance increase would be about 8 yards.

However, launch angle and roll have a huge effect on the golfer's realization of distance. If the new thin-face driver delivers a better launch angle with less backspin and generates a more driving trajectory that carries some 8 yards with higher ball velocity could deliver as much as 20 yards more distance.

Is there difference between thin face and variable thickness faces on wood heads?
While no real definitive between testing has been done on such a comparison, there is a difference. Some of the thinner face drivers are made with the face all one thickness while others are being made with the face varying in thickness.

Currently, the Callaway ERC drivers - sold in Japan and Europe - heated up the spring face debate, and is the only driver of which the Golfsmith team is aware with variable face thickness. The ERC face is a little thicker in the center than the outer periphery Callaway say this spreads out the maximum face deflection.

No matter whether a face is consistently thin or intentionally variable in thickness, the impact with the ball is still dictated by the head's COR, which has a real limit imposed by the side difference between the weight and material of the clubhead and the ball. In addition, because there is only a difference of 8 to 10 yards between the highest COR driver today and the tradition thick-face woods of five years, any performance difference between a consistently thin and a variable thin-face driver would be minimal at best.

What will I feel when I hit a thin-face driver?
While the sensation of feel during impact between the clubhead and the ball varies from golfer to golfer, most people who are matched to a thin-face clubhead that is right for their swing speed use the term 'hot' to describe the feeling of impact to the ball. To translate 'hot' into a more realistic description, the 'hot' feel equates to the clubface flexing the face with a higher velocity.

Regarding of whether the face is thin, if that particular level of face 'thin-ness' is NOT matched to the golfer's swing speed, the impact will feel pretty much like any other thick-face clubhead.

But two things are certain when it comes to thin-face designs, particularly with drivers and to a lesser extent with fairway woods. First, the right ones increase distance and the wrong ones don't. Secondly clubmakers still have to fit all the club specification as correctly as possible as to the player's needs. That's one rule that can never be overlooked, no matter how thin you slice it.

Philip Ang 1999-2000 Winner International Clubmaker of the Year
conferred by Golf Clubmakers Association (GCA) - USA compiles this article from Golfsmith Tech Report.