Iron Testing for Distance

There comes a time in every golfer's experience when the question of whether a different combination of components would yield more distance from the same swing. We all ask it, and seeking the answer is one of the great pleasures in golf.

Recently we worked with a golfer with a powerful swing who was ready to test everything reasonable in pursuit of perfection. Our radar launch monitor and fitting system with exchangeable heads and shafts are ideal for this purpose.

We set up an exhaustive session, and to minimize bias we varied 6-iron combinations in random order throughout the test, with 6 - 12 shots hit for each combination. 

We plotted the data in different ways. In testing irons for distance, carry distance and shot dispersion have the most meaning. It's target golf where where we measure the key variables. Here are the averaged results for each head/shaft combination focusing on carry distance. 

Does club fitting make a difference? We think the data answer the question and underscores the old cliche, "if you don't test it's just a guess". Which combination do you think is the best improvement over the player's current iron setup?

Fitting Beginners

A frequent question from golfers who are just beginning to play golf is whether it makes sense for them to get club fitting now or wait until they get better at playing the game. Can club fitting help them? The answer is an unqualified yes, and here's why. 

Almost everyone who takes up the sport of golf starts with clubs that do not match their physical traits and abilities. Typical clubs we see are "beginner sets" from big box discounters, online auctions, used hand-me-downs from friends or family, etc. Unfortunately these clubs are often too stiff, too heavy, too long, too soft, all of which lead to performance results that are inconsistent or worse.

Learning and practicing with clubs that don't match well with your body and swing characteristics means you are grooving your game to equipment that will limit your ability to play consistently and effectively. Distance and accuracy suffer. You make subtle and not so subtle compensations in your swing to achieve your goals. It leads to more problems and more corrections.

A professional club fitter will schedule an appointment to help you get what's needed to learn and play the game as you envisioned it. A partial set with clubs that have the right length, weight, balance, stiffness feel, and effective performance designs is the goal. You get just the clubs you need with the right mix of lofts and function -- a good set makeup saves you money that can be spent on top quality components. 

With an effective set makeup in your golf bag, lessons and practice become more effective. Playing becomes more enjoyable. You develop a swing that allows you to progress faster and further than otherwise possible. You will get more enjoyment from the game at every level of experience.

Swingweight or MOI?

Swingweight of a golf club is a measure of mass distribution around a fulcrum point located 14 inches from the grip end. An arbitrary scale of letters and numbers (e.g. C6, D2, etc) indicates the swingweight. 

MOI of the golf club is a measure of the resistance the club when swinging it around an axis of rotation located at the grip end. It's a indication of the energy required to swing the club.

Both swingweight and MOI give a sense of how the clubhead weight feels in relation to the length of the club during the swing. When the swingweight of all clubs in a set is constant the long irons will have a heavy head weight feel and the short irons will have a lighter head weight feel.

When a set is MOI matched, the head weight/length feel relationship is reversed -- short irons have a heavier head weight feel than long irons. MOI-matching makes long irons feel easier to swing than swingweight matching. MOI-matching yields an improved sense of control with the short irons. MOI-matched irons promote greater consistency in the swing through the set.

The great majority of golfers who compare the feel of a constant swingweight-matched set vs. an MOI-matched set in blind testing find MOI-matched clubs have a more consistent swing feel through the set. They prefer MOI-matched sets over swingweight-matched sets for their game.

We see the preference for MOI-matched iron sets in golfers of all skill levels and handicaps. The preferred MOI varies for each golfer -- clubfitting identifies the preferred MOI for each golfer. An MOI vs. swingweight test can be done by any golfer with their own set using lead tape to change head weights on their irons. 

Retail "off-the-rack" iron sets are built by the OEMs to have constant swingweights. It's done for easier bulk manufacturing and to simplify inventory stocks for retailers. Essentially, iron sets are built for the convenience of the OEM and the retailer, not for the performance preference of the golfer.

The MOI-matching option can be a significant benefit of custom iron and wedge sets. A professional fitting process identifies the optimum MOI match to your swing, then the set is built to match your swing specifications. MOI-matched clubs make it easier to achieve swing consistency, a key frontier for reaching lower scores.

Meaning of Shaft EI

Shaft EI stiffness profiles have come of age in characterizing the flex of a golf shaft. EI profiles have replaced shaft butt flex -- the typical L,A,R,S,X designation of flex in its various forms -- as the key measurement of how a shaft bends during the swing. What is EI and how does it help you get fit for the right golf shaft to match your swing?

EI is an engineering term that describes the effects of shaft material elasticity (E) and geometry (I) on resistance to bending -- e.g., stiffness. The distribution of stiffness along the length of a golf shaft depends on the materials used and its construction techniques in manufacturing. Graphite fiber properties and resins that bind graphite fibers (E), as well as wall thickness and local shaft diameter (I) are among the many factors that contribute to EI. 

Why does EI matter? A golfer who begins the downswing with a powerful pulling movement will put different bending forces on the shaft than a golfer who begins the downswing with a smooth gradual movement. Similarly, at impact an early wrist release, a late release, a hold and flip release, and wrist rotation - flexion - supination changes exert distinct bending forces on the shaft. Matching EI stiffness properties to these swing mechanics bending forces has major effects on distance and accuracy. It's the heart of modern clubfitting.

The most detailed and useful EI data comes from a 3-point measurement system. The shaft is held by thin supports located 10 inches apart, a calibrated weight is lowered onto the mid point of the shaft between the supports, and strain resistance is quantified. Measurements at one-inch intervals yield an EI graph that shows how stiffness is distributed along the length of a typical shaft. Deriving EI graphs by alternate methods lacks the resolution of 3-point systems.

To see how EI helps us, here are EI profiles of four driver shafts from the same manufacturer designed for different performance properties. We compare the data to deflection graphs in which the bending resistance of the shaft is measured at 2-inch intervals from the tip in response to a standard deflection force applied to  the tip.

Deflection is widely considered a direct indicator of how the shaft might respond to bending forces during the swing -- think of the inertial resistance of a clubhead in the downswing as equivalent to the tip deflection force in our measurement system. The two graphs show that stiffness engineered into the tip region affects bending in mid to butt region. 

These four shafts have the same butt flex and same total weight. The EI plot from butt to mid section is quite similar in all four shafts. In contrast, the Tip to Mid sections show substantial EI differences. The red-line shaft has an increase in stiffness peaking 16 inches from the tip, the green line shaft has a stiffness peak 14 inches from the tip and at lower magnitude. Both blue-line and orange-line shafts have linear changes in EI with the orange-line shaft having a softer tip than the other three shafts.

In measuring deflection, the shaft butt is immobilized and the amount of force required to displace the tip by a constant amount is measured. Greater force is required to deflect the red-line shaft than the other shafts, and resistance to deflection is distributed throughout the shaft approximately proportional to EI differences limited to the tip region. 

These graphs show that increased EI stiffness in tip-mid regions of the red-line shaft and green-line shaft transmits greater bending resistance to the mid-butt regions where EI differences are minimal. The position and magnitude of the tip EI peak affects the extent of deflection in the mid-butt region. These effects are consistent with why shafts that measure the same butt flex by widely used low-resolution L,A,R,S,X methods can have large differences in performance and feel for different golfers. 

To get full clubfitting benefit from knowing the details of shaft stiffness distribution, we need to determine how and where a golfer transmits maximum rotational energy to the club in the downswing. The goal is to select a shaft that allows for maximum clubhead speed to be delivered to the ball at impact. Clubhead speed translates directly to distance. Shaft stiffness distribution, together with shaft torque properties, also influence clubface orientation at impact, a key factor for accuracy.

Data from the 3-point EI measurement system yields insight into stiffness distribution along the length of the shaft. Swing analysis using a combination of 3D motion capture (e.g., the K-Vest) and high speed video reveals the kinematic sequence and key mechanics of how a golfer swings the club. Taken together, these technologies help a golfer find the right shafts for their clubs.

jtclubs San Francisco, Dec 2014

Use Stats to Improve

Statistics can form the basis for improving your game. We think it's a great way to determine what clubs in your bag need upgrading. Forget shopping for the whole set before you know what you need. Spend your money wisely on the best possible clubs that will have the biggest impact on your scores.

Start with a simple smartphone app for tracking shots. Distance and accuracy for each club is probably sufficient. You can get carried away with statistics, but let's focus on what's most important. What distance do you get for full shots and how far away from your intended target was that ball at impact. And note shot quality -- did you get the intended ball flight trajectory? We don't care about much else. 

To minimize the data collecting effort, start with your wedges and putter. Unless you routinely hit greens in regulation from more than 150 yards, focus on the recovery part of the game. There's an almost certain chance that if you're playing popular off-the-rack wedges you will find the short game is a must fix part of your game especially at the high loft end of the set. 

For example, how many yards do you hit your sand wedge? How far from the target spot -- you should always select a specific spot where you want the ball to land -- is the ball impact mark? Did the ball land left or right or far or short of where you wanted it to go? Was the ball flight too high, too low, hooked to the left, or screaming in pain to the right?

Take a similar approach with your putter. Track your distance control. How far from the hole is the ball when it comes to rest? Do you miss right or left or far or short? OK, we get it about technique, but let's be sure you have the best instrument in your hands before you work on your skills. If you practice with a junk putter you will not develop a great putting game. You need a putter that fits your stroke tendencies.

We view statistics as an important part of knowing your game. Data and testing enhances your ability to make the best club selections for your game. Forget the marketing claims, club reviews, and discount prices. Start with data. It will help you focus on one shot at a time and increase playing enjoyment.

Then, take the data and work with a fitter who knows what to do with the results. The real advantage of the data now become apparent. Remember, 2/3 of your score comes from the wedges and putter. That's where you want to spend the money first. Work backwards from the green when building your set. Custom fit wedges and putters make sense when viewed from that perspective.