Golf Ball Spin Axis

A golf ball spins around an axis of rotation during it's flight. The axis of rotation is often termed the spin axis. The forces that create spin are surprisingly complex, but we can stick to just a few basic concepts to understand how the spin axis relates to the ball flight we see on the course. 

At impact the ball develops back spin around a single axis of rotation: club loft and club face curvature are major factors in determining spin and launch angle. The spin axis can be horizontal or tilted but it remains a single backspin axis -- "there can be only one". However, spin is an axial vector and can be considered to be the product of a vertical component and a horizontal component. It allows us to say "side spin".

The direction of the club path and the direction of the launch angle of the ball off the club face also can be considered as vectors. These two vectors define the geometric plane of the ball during the initial flight of the ball after impact. The geometric plane that describes initial ball flight, the D-plane (a term defined by T. Jorgensen in "The Physics of Golf" 2nd Edition 1999), is perpendicular to the spin axis.

If the orientation of the club face is exactly the same as the club path at impact, the ball will have a spin axis of 0º and the ball flight will be straight. If the face angle of the club is oriented in a different direction from the path of the club head at impact, then the ball spin axis (and D-plane) will be tilted and the ball flight will curve.

For a right handed player, if the club face is oriented to the right (open) of the club path, the spin axis will tilt to the right and the ball may fade or slice to the right. If the face is oriented to the left (closed) relative to the path the spin axis will tilt to the left and the ball may draw or hook to the left. 

Launch monitor analysis reveals that face angle is more important than club path in describing ball flight curvature. Just a modest amount of open club face at impact can yield a banana-shaped ball flight, an effect that's more noticeable with lower-lofted clubs.

Ball impacts that are not in the center of the club face also affect spin axis. These effects are increased with drivers compared to irons where the center of gravity of the club head is located further behind the club face allowing gear effects to magnify the tilt of the ball spin axis. An impact more than a half inch off-center can tilt the spin axis by greater than 20º.

Analysis of the factors that alter spin axis helps to isolate and quantify problems in your swing mechanics. For example, the effects of a backswing that's too far inside with an open club face, a loss of posture through the downswing, an outside-in club path with a loss of posture (standing up) through the impact zone will be revealed by launch monitor data. 

Ball spin axis can be affected by each of these swing traits, and the effects can be magnified by a shaft stiffness profile or a club balance that does not fit your swing mechanics. If you are a golfer at any skill level who wants to refine your game, we recommend integrating both launch monitor and swing mechanics analysis into your search for the "right stuff".

MOI Matched Clubs

Matching irons and/or wedges to the same MOI as measured at the grip end of the clubs results in sets that have a consistent sense of feel for every club in the bag. The short irons have the same swing feel as the long irons. The same effort is used in swinging each club. It promotes consistency and repeatability in shot making.

We have been building MOI-matched irons sets for more than ten years. It's long enough to learn that MOI matching yields more consistent club performance than swingweight match sets. Swingweight matched irons are built to a single club factory standard. In contrast, MOI-matched clubs are built to complement each individual golfer's swing movement pattern through the set. Custom MOI-matched is always better.

It's possible to build a complete set of clubs, driver through fairway woods, hybrids, irons, and all wedges, to have the same MOI. It means that if you have experienced club fitting that determines your optimum MOI, then swinging every club will involve the same kinetic energy. A golfer who is in control of their swing technique will experience extra-ordinary performance from a fully MOI-matched set through the bag.

Sets built to these standards break many of the traditional rules or guidelines for building club sets. The typical standard that woods and irons can be built to the same swingweight, and that wedges are often built to someone else's standard make no sense given today's understanding of performance optimizing.

In our experience, MOI-matched clubs through the entire set can transform your game. Without conscious effort, you stop being concerning about bringing a different swing to each club. Your focus at address is entirely on optimizing your swing technique because the clubs already perfectly complement your golf movement pattern -- your swing mechanics.

We find that realizing the full benefit of MOI-matched sets requires building to a higher level of spec tolerance than is generally done in any shop, and that factory built sets just can't achieve this goal and have all necessary inventory choices. But when tight tolerances are the basis of custom MOI-matching in the build, your game can reach a new level of consistency.

As a typical golfer who searched for consistent performance from the entire set of clubs in my golf bag, it wasn't until close MOI-matching was fully built in that this ethereal goal seemed within reach. It's experienced in performance on the course, the only place it matters.

Golfers who are on a quest for the lowest score they can achieve owe it to themselves to play custom built clubs that are closely MOI-matched -- to a tolerance level that far exceeds what is generally recommended. We think it's the holy grail of club craftsmanship.

Stock or Aftermarket?

A key question in buying new clubs is whether to get the stock shaft "off-the-rack" or upgrade to an aftermarket shaft. The answer is clear: there is no way to know which shaft is best for your swing without testing. The only way to avoid guesswork is by clubfitting with a broad selection of high quality shafts.

We recommend testing with aftermarket shafts that are manufactured in the shaft company's home factory. The benefit of recent technology is often compromised in shafts that have been contracted out to large bulk production manufacturers who substitute lesser quality graphite and materials to lower costs and meet price targets of the large golf companies. 

Aftermarket shafts in club fitting should include models with the most recent technology including new graphite formulations and construction techniques. We have been recommending specific new lightweight driver shafts to golfers and others in the golf industry because of their positive impact on club head speed and ball flight performance on the course where it counts.

Shaft testing is most effective when it's done with a radar launch monitor that can measure ball trajectory, ball velocity, ball spin, launch angle, club head path, and club head speed.

These factors are the key measurables that allow reasonably accurate calculation of carry distance (more meaningful than total distance), ball dispersion, and ball spin axis (essential for understanding ball flight). Measuring face angle requires a high speed camera with an effective orientation to the club head at impact.

Why is it important to do direct testing instead of following charts and online recommendations? It's because each golfer responds uniquely to the stiffness and weight distribution in any given shaft design -- what works best for your friend may not work best for you. The combination of swing mechanics variations and shaft stiffness/weight/torque differences is greater than current analytics can resolve. It's why direct shaft testing is the most effective way to match the right shaft to your swing mechanics.

Lightweight Shafts

We have been testing new lightweight graphite shafts for drivers, and new lightweight steel shafts for irons. They have transformed our view of the performance that can be expected from golf clubs built with these radical new designs. The reduction in overall club weight facilitates faster club head speed and yields increased distance.

The key to the performance of these shafts is in the distinct properties of the materials and construction techniques used in production. New graphite materials and steel alloys allow for thin but strong shaft walls that remain stable under the changing forces in a downswing and through impact. The distribution in stiffness, torque, and weight distribution along the length of the shaft can be engineered to achieve predictable responsiveness for different swing styles.

Driver shafts weighing ~50 g or less reduce the MOI of the club making it easier to swing at faster club head speeds. High structural stability and moderate to low torque through the mid and tip sections reduces shot dispersion thereby resulting in improved control and accuracy. Lightweight driver shafts especially benefit players with moderate swing speeds and a smooth swing tempo.

For irons, retaining a soft but stable feel in steel shafts has finally been achieved with new alloys and production methods that can make them the preferred choice compared to conventional graphite alternatives. Steel minimizes the consistency problems that often plague the bulk manufactured graphite shafts typically found in off-the-rack clubs.

Not all lightweight steel shafts have the same responsiveness since alloys and production strategies vary among manufacturers. Differences in shaft playability are magnified in players with a smooth tempo compared to players who have a strong attack early in the downswing. 

We encourage golfers to play custom fit lightweight clubs and discover the benefits to their game. Players at all skill levels will see improvements that are simply not found with traditional component weights. Performance of irons with built with these new lightweight steel shafts can be liberating.

Single Length Iron Set

Interest in single length irons has always percolated along in golf. The concept is that a single length set will make it easier to generate the same swing for every club in the bag since the ball at address is the same distance from the player for each club. To achieve optimal performance, all clubs should have the same swingweight and MOI. 

In single length sets all clubs are typically built to a 7-iron or 8-iron length. To retain swingweight consistency, weight needs to be added to the club heads of long irons and removed from the short iron club heads. Consequently the practical range for building a single length set is from the 5-iron to the sand wedge to maintain the same MOI for all clubs.

A key benefit of single length sets comes from reducing the length of the long irons. Improved club face impact performance can be achieved. The extra clubhead weight needed for the 5-iron and 6-iron can be easily accommodated for most shaft choices and club head designs. De-lofting long irons may also be a possibility for increasing distance if your swing mechanics permit.

Since single length high-loft wedges can be an inch or more longer than in traditional length sets, lighter weight club heads are needed to maintain swingweight consistency. It places a major restriction on building wedges and short irons since component options are limited. The recently developed Wishon Sterling single length set may be the best if not the only option available.

Low-loft fairway woods and hybrids would require significant design changes if you want them in a single length set. Your driver would be replaced by a fairway wood. But if you find hitting a 3-wood off the tee achieves similar distances as your driver, that may not be a problem for scoring low and enjoying the game.

For those players who want maximum control of their short game and a little extra distance off the tee, an MOI-matched set can be built ranging from driver though high-loft wedges to allow any golfer to swing each club with the same effort. Length differences between clubs would be minimal. Most club head styles available currently can be used. 

MOI-matched sets facilitate shot-making consistency because the same effort is used for every matched club in the bag. We've tested just about every reasonable club building option during the past 15 years finding that new shaft and clubhead technology has allowed for extending MOI matching through the set with desired performance improvements that overcome the limitations of single length sets.