The Spin On Center Of Gravity

If you've been reading my golf tips newsletter, scanning golf Web sites, or perusing golf magazines, you've probably come across the term center of gravity (COG). More than likely, you've seen the term in conjunction with ads for or an article about golf clubs. That's because it's one of the hottest concepts in golf club manufacturing technology, along with moment of inertia (MOI). And like many recreational golfers, you probably wondering what COG is and how it affects your game.

Actually, the concept isn't new. It's been around for years. What's new is its execution. Thanks to advances in golf club manufacturing technology and golf club research and design, center of gravity is a concept whose time has come. And while it's not a term you'll hear a lot about during a golf lesson, it's a term you should know because it can have a decided impact on your golf handicap.

COG Defined
One golf Web site defined center of gravity as "the point within the head of a golf club at which it would be perfectly balanced." That's as good a definition of COG as any I've read. Technically, COG is determined by balancing the clubhead on its face, sole, or any place on the head - the intersection inside of the head of all these different balance points is the center of gravity of the clubhead.

Since the center of gravity is a single point inside the clubhead, its location has to be defined in 3-dimensions. There's a vertical COG location (how high up in the head the COG is from the sole), a horizontal COG location (how far over it is from the center of the shaft in the hosel of the head), and a depth COG location (how far back from the face it is located). If you alter the position of any of these points, you alter both the COG and the club's performance.

Position of COG
The position of the center of gravity within a clubhead alters both the trajectory and the accuracy of shots. A COG position that's low and toward the back of a clubhead encourages a higher trajectory for any given loft angel on the club. On the other hand, the closer the COG is to the shaft, the less a golfer tends to hit a ball offline. The farther the center of gravity is from the shaft, the more a golfer tends to hit the ball offline.

In theory you would always want the COG in line with the center of the clubhead's face. But moving the COG helps "mitigate" some swing flaws. That's great for those of us who don't hit the ball in the face's center, which judging from my golf lessons and my experience in general, is the category where most recreational golfers fall. The more the designer incorporates perimeter weighting in the clubhead's design, then, the better off a recreational golfer is with the club.

COG also alters ball flight, which is good for players with some ability. Moving the COG toward the heel helps you hit a hook. When contact occurs away from the center of gravity, the ball's axis of rotation tilts toward the heel. That imparts sidespin, causing the ball to move. However, as moment of inertia (MOI)the relative stability of off-center hitsincreases, the more you have to move the COG to produce the sidespin you need to hook the shot.

Impact of COG
What does all this mean for a golfer and his/her golf handicap? When you're buying golf clubs, research the COG of the clubs your considering. Since you're not a professional, look for a club offering the best center of gravity for your caliber of play. Cavity-back irons, for example, where the COG has been moved more toward the club's outer edges are great for beginners because they're more forgiving of off-center hits, which means the new golfer find the fairway a lot more than with clubs lacking perimeter weight design.

However, be careful when considering clubhead design. Manufacturers often add or subtract design features in an attempt to make their clubs perform better and differentiate them from other clubs. Some "improvements" impact COG, which means they will affect the clubs performance, too. What you need to do is find the clubhead that works for you, test the club if you can. Testing is the best way of determining if a club is right for you.

Now that you know what center of gravity is, take advantage of it the next time you're in the market for new clubs. COG will impact a club's performance, including trajectory and accuracy. That in turn impacts your golf handicap. For best results, look for a club with a center of gravity that fits your game.


Copyright (c) 2008 Jack Moorehouse