How Golf Clubs Work


Golf clubs come in woods, irons and putters. See more sports pictures.
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When Tiger Woods won the 2000 U.S. Open, it took four days for the championship to be decided. He was on the course for several hours each day and he finished with a score of 272, which means he hit the ball 272 times. We also know he moved the ball at least 27,372 yards, because that's the length of the Pebble Beach course multiplied by four. But the total amount of time his clubs were in contact with the golf ball during the four days adds up to only about one-tenth of a second!

How can this be? What actually happens when a club hits a golf b­all? Does it really make any difference how the club is designed, or are the new high-tech clubs just so much marketing hype? In this article, we'll examine those 450 millionths of a second that make up a single strike of a golf ball to learn how golf clubs send a golf ball sailing from tee to green.

Types of Clubs

Different clubs in the golfer's bag are designed for different uses on the course. We'll explain more about what makes them different when we describe the parts of a club, but here are the clubs:

  • Woods are the longest clubs in the golfer's bag, the clubs with large, bulbous heads designed to send a golf ball sailing hundreds of yards with a single swing.
  • Irons are present in the greatest variety, from the low-numbered clubs designed to hit a ball nearly as far as a wood, to the high-numbered irons and wedges designed to send the ball a short distance in a high, arcing trajectory.
  • Putters are built for finesse, designed to help guide a golfer's aim and steady her hands as they send the ball rolling into the cup from a short distance.

Parts of the Club

Any golf club has three basic parts:

  • The grip - the part you hold
  • The shaft - the part that connects the grip to the head
  • The head - the part that actually hits the ball

If you walk down the golf club aisle of a large sporting goods store, you'll see a variety of designs for all three of these parts, but you'll also notice that all clubs have certain similarities. That's because every golf club used in a round of golf that's either part of a tournament or that might count toward a golfer's handicap must conform to rules established by one of two organizations. In the United States, the rules of golf, including golf club regulations, are established by the United States Golf Association (USGA). The rules of golf for the rest of the world are established by The Royal and Ancient Golf Club of Saint Andrews (in Scotland). For the most part, the rules established by the two bodies are the same, though there are some differences. Now let's look at the main parts of the club.

The Grip

The grip of the golf club is important because it connects the club to the golfer's hands. According to the rules of golf, recognized by both ruling bodies, the grip has to be round, without obvious bumps, lumps or hollows. You'll see grips made of rubber or leather with an assortment of small holes, grooves or ridges. All of these qualities are designed to make it easier for the golfer to hold onto the club without making the grip so large that it will run afoul of the rules. There are various sizes of grips to accommodate different hand sizes and grip styles. According to most experts, the ideal material and design of the grip are a matter of personal preference.

The Shaft

The shaft of the golf club connects the grip to the head and, like the grip, must be basically round in cross section. Most modern golf club shafts are made of either steel or a carbon-fiber and resin composite. Carbon fiber has the advantage of being lighter than steel, but clubs with carbon-fiber shafts also tend to be more expensive. In addition, some golfers say that hitting a golf ball with a carbon-fiber club feels different than hitting the ball with a steel-shafted club. This difference arises because steel and carbon fiber transmit vibrations differently. As in grips, shaft material tends to be a personal preference.

The stiffness of the shaft is another variable. Most manufacturers rate their shafts in one of six degrees of stiffness. From least to most stiff they are:

  • L - Ladies
  • A - Seniors
  • R - Regular
  • F - Firm
  • X - Extra Firm
  • S - Stiff

As you can see, there isn't a grade for "wobbly" or "limp." Most golfers, at least in the United States, seem to prefer a shaft that is stiffer, and manufacturers have obliged. But if golfers prefer stiffness to limpness, why not make everything super-stiff? The answer has to do with distance and strength.

If you're Tiger Woods, or if you swing a golf club as he does, your body will coil and uncoil during a golf swing so that you apply plenty of energy to the face of the golf club when it meets the ball. If your swing is this good and if you are this strong, you want a very stiff shaft so that every bit of energy you generate in your swing is delivered to the ball, and none is absorbed in making the shaft of the club bend and vibrate.

If, on the other hand, you do not have a Tiger Woods swing, then you can get a shaft with some flexibility to do some of the work of sheer muscle with a well-timed "whip" motion that stores energy from the top of the swing in a bent shaft, then releases it in time to deliver that energy to the ball. How much flex might you need for your particular swing? If you're serious about answering this question, then you should have a golf pro (a club professional who's a member of the PGA of America) analyze your swing and make a recommendation.

The Head

The head of the golf club is where all the energy of the swing is transferred to the golf ball. There is more variation in the appearance of golf club heads than there is in either shafts or grips, but all the variations fall into one of three broad categories: the heads of woods, irons and putters.

A club's "sweet spot" marks the middle of the club face -- the ideal place to hit the ball. A club's "sweet spot" marks the middle of the club face -- the ideal place to hit the ball.
A club's "sweet spot" marks the middle of the club face -- the ideal place to hit the ball.

Woods

Woods have the largest heads of any golf club. These large clubs are designed to send the ball 300 yards or more with a single swing. What is it about the bulbous shape of the wood that suits it for these long-distance strikes? The answer has to do with the wood's shaft, especially in the largest wood, called the driver. Wood shafts are considerably longer than the shafts of most other clubs. This length increases the power that can be transferred to the ball, but it also makes it less likely that the ball will meet the the quarter-sized sweet spot in the middle of the club face. When an off-center hit occurs, the head of the club tends to twist, pointing the face in an unintended direction, and sending the ball the wrong way.

A golf club designer has to balance a number of factors. A heavy club head best resists twisting and so suffers the least from a less-than-perfect swing. On the other hand, a golfer can generally swing a club with a lighter head at a greater speed, which generates more energy to be transferred to the ball and so sends the ball a greater distance. Over the past 100 or so years, golf club designers have attempted to strike a balance between light and heavy clubs. The large head of a driver and the combination of metals like steel, titanium and bronze that go into various drivers, are attempts to balance stability and light weight. The driver head shape allows designers to move the weight in the head to points that enhance stability (points that are different for each brand of club, and provide one of the differences touted by manufacturers when claiming superiority for their clubs). The driver head shape also allows the head to glide over grass and ground rather than digging into the turf.

Irons

Irons are designed for a greater variety of shots than woods. Where woods tend to be optimal for long to very long shots, the shots made using irons range from 200 yards or more, in the case of 2 irons, down to 40 yards or less in the case of the various wedges. Club designers must cope with the same issues in irons as in woods, but their shorter shafts and the less exaggerated swings with which they are used have led to different solutions for different types of players.

Only 25 years ago, most companies' irons were very similar -- a blade-shaped head with most of the weight concentrated low and in the center of the club. This design gave an additional emphasis to shots in which the ball was hit with the club's sweet spot. The heads of these clubs were steel, and usually shaped by forging -- hammering hot metal under great pressure. When a golfer hit the ball off-center, there was very little in the club's design to prevent it from twisting and delivering a disappointing shot.

In the last 25 years, designers have developed clubs that have approximately the same weight as the older clubs but have it distributed around the perimeter of the club, so that the head is far more resistant to off-center twisting and therefore far more forgiving of golf swings that are off line by a few millimeters. In addition, modern metal alloys have allowed for larger iron heads, which increases the size of the "sweet spot," thereby increasing the possibility of good results with a less-than-perfect swing.

If you look in the golf bag of a PGA Tour player, you'll probably see the same sort of forged blade-style irons you would have seen 25 years ago. That's because their concentration of weight behind the sweet spot make the most of a professional's very consistent, very accurate swing. Recreational golfers, on the other hand, have embraced the perimeter-weighted iron for the good results they get even with less consistent swings.

Putters

Putters have a relatively simple job: to strike the golf ball with a face perpendicular to the path of a gentle swing and cause the ball to roll along the ground until it falls into a hole. Twisting is still a concern with off-center hits, but a putter is designed to transfer far less energy to the ball than either irons or woods. It's interesting, then, to note the incredible array of shapes taken by the heads of putters -- blocks, blades, short, long, thick, thin, etc., and the various patterns of lines found on the faces. So why is there such variation in a club designed for such a simple task? Because the mechanical simplicity of putting places most of the pressure on the golfer's mental processes, where there is room for far more variation than in any golf swing.

The Parts of the Club Head

The head of the golf club has several parts: the hosel, where the head connects to the shaft; the face, which actually strikes the ball; the sole, which is the part closest to the ground; and the back, which is on the side opposite the face. We've talked a bit about the design of the back, and there's not much to say about the hosel, so let's look at the face and the sole.

The Face

When you hear an announcer for a golf tournament talking about the player's selection of a club, you'll generally hear whether the player has chosen a wood or an iron, and then a number. The number is related to the angle at which the face slopes back from vertical when the club is held in its normal position facing the ball. A higher number for the club represents a greater degree of slope away from vertical, generally resulting in a higher, shorter shot. There are some slight variations between manufacturers, but the club numbers and their related slopes generally look like this.

The slope is important for two reasons. First, the face will launch the ball on a path perpendicular to the plane of the face at impact, so a more "laid back" face will start the ball on a higher trajectory. This is crucial when a golfer tries to send the ball over some obstacle, or when the golfer wants the ball to come back down at a steep angle, which tends to result in a shorter roll after landing. The second important aspect of the slope is spin -- the greater the slope, the greater the spin.

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In the 450 millionths of a second that the ball and club are in contact, as shown in the animation to above, the ball does several things. First, it deforms quite a bit, flattening against the face of the club. As the ball begins to rebound to its normal globe shape, it starts to slide up the club face. Finally, just before it leaves the club, the ball returns to its familiar shape and begins to roll up the face. By the time the ball has left the club face, it is spinning quite rapidly. According to the USGA, a ball hit by a wood or one of the longer irons (3 to 5) will be spinning at approximately 3,600 RPM when it leaves the club. The same ball struck by a pitching wedge will spin at nearly 6,000 RPM when it leaves the club.

A spinning golf ball is a good thing because the rapid spin provides aerodynamic lift, causing a spinning ball to travel higher and farther than one with no spin at all. The spinning ball is also less influenced by small gusts of wind, making for a more predictable shot. One of the other features you will notice on the face of a golf club, the grooves, also help provide spin.

The grooves on the face of a golf club serve two purposes. First, they provide just a bit of "bite" for the golf ball as it's sliding up the face, helping it to spin more rapidly. Next, if grass is trapped between the ball and club at impact, the water in the grass will be squeezed out by the nearly 3,000 pounds of force generated by the average swing. Like the tread on an automobile tire, the grooves on the club face give the water somewhere to go so that the ball doesn't skid up the face without spinning.

The Sole

Ideally, the sole of the golf club will minimize the twisting of a bad hit. In woods, the broad, flat sole with rounded edges helps the head glide over the surface of the grass without digging in. Shots using irons tend to take patches of the turf away (the patch is called a divot), so the sole of irons are designed to slice through the turf evenly, without twisting or unexpected tugging to disrupt the golfer's shot.

The Most Important Part: The Golfer

Mark Twain called the game of golf "a good walk spoiled." Golf club designers have tried to make it more difficult for golfers to spoil their fine walks with bad shots. Many golfers say the new forgiving clubs make a huge difference in their game. Variations are available for all levels of strength and experience, but choosing the right club and using it well are up to the golfer.

A poor choice of club and a bad swing can still produce the worst of shots from the best of clubs. And that's a good thing because it means the quality of the golfer is still of some importance in the game of golf.

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