Science of Impact: Recent breakthroughs prove you need two swings to score low

April 19, 2012

For decades, players seeking the secret to the swing usually needed the trained eye of a teaching professional, whose knowledge of conventional ball-flight laws could help the average Joe straighten out his crooked shots. Then along came video, which revealed flaws and fixes invisible to the naked eye. Still, swing mysteries persisted. But not anymore. In recent years, TrackMan's use of Doppler radar has ushered in a new era of swing- and ball-flight-tracking devices, unveiling heretofore hidden dynamics, especially at the most important part of the swing — impact. This state-of-the-art technology has not only exposed what's really going on when your iron or driver makes contact with the ball. It has led to a surprising — check that, game-changing — discovery: You need not one but two different swings to play your very best. Here's how to finally get your swing — make that swings — on the right track and hitting your target every time.

Pop quiz, class. Place your books under your desk, and no copying.

"D-Plane" is:
A) What you do after your flight ends.
B) A quote from the classic TV show Fantasy Island.
C) The impact theory that's changing the way you swing.

If you chose "C," you pass. While it may be a new concept to you, the D-Plane dates back 20 years. In 1993, Dr. Theodore Jorgensen, a University of Nebraska physics professor who had worked on the Manhattan Project during World War II, published The Physics of Golf. In it, he coined the term "D-Plane," which he called "the plane located between the intersecting lines created by the clubface angle and clubhead path". He postulated that variances in your D-Plane — that is, different combinations of clubface angle and clubhead path — directly determine your ball speed, launch angle, spin rate and, as a result, your shot patterns, straight or crooked. And he based it on the proven laws of physics. For decades, teachers had only hypothesized about how path and face angle affected shot shape (the human eye and video can only see so much, especially at impact). Dr. Jorgensen had dug much deeper.

A decade passed before the technology existed to test Jorgensen's theory. Enter inventor Fredrik Tuxen, whose Doppler-radar based TrackMan device measures seven clubhead and 15 ball-flight parameters. For the first time, clubhead movement through impact could be viewed and analyzed in dynamic 3D. Tuxen's team confirmed that attack angle, clubhead path and clubface angle at impact are the absolute keys to controlling ball flight.

"We got valuable 3D data on exactly how the clubhead moved on the lower arc of the swing and through impact," Tuxen says. "We realized that the initial direction of the ball is dominated by the orientation of the clubface, rather than clubhead path — but a lot of us were taught just the opposite. The truth is, it's a combination, with about 85 percent depending on clubface angle and only 15 percent depending on the path of the clubhead."

Armed with this new data, Tuxen has revealed perhaps one of the most counterintuitive swing findings ever: To hit a straight shot off the ground with an iron, you must strike the ball with a descending angle of attack and an outside-in swing direction; to hit a straight shot with a driver, you must ideally strike the ball with an ascending angle of attack and an inside-out swing direction.

In other words, to make the ball go where you want it to, you need two unique swings.

"Now that we have equipment that measures precisely what's happening at impact, instructors can help their students address ball-flight issues. If you're not happy with the direction or shape of your shots, simply look at your TrackMan data, see what's wrong, and then go fix it."

On every impact between ball and club, the clubhead path and clubface angle intersect. This intersection can form an infinite number of D-Planes. When you make impact with the clubface aiming in the same direction that the clubhead is moving, the D-Plane is perfectly vertical, resulting in a straight shot. The D-Plane tilts when you get your clubface and path pointed in different directions, and a tilted D-Plane means that the ball is going anywhere but straight on a center-face hit.


Angus Murray


Because you ideally make contact before the club reaches the bottom of its arc when swinging an iron, the clubhead path is still pointing to the right. This, combined with a square clubface, will draw the ball to the left.

D-Plane Iron

Karen Ha


Because you ideally make contact after the club reaches the bottom of its arc when swinging your driver, the clubhead path is pointing to the left. This, combined with a square clubface, will fade the ball to the right.

D-Plane Driver

Karen Ha


Thanks to TrackMan technology, instructors can now analyze impact as though it's happening in ultra slow-motion. One of the best at this is Golf Magazine Top 100 Teacher Brian Manzella (English Turn Golf & C.C., New Orleans). Says Manzella, "To hit straight shots, you need to — using TrackMan lingo — 'zero out your numbers.' " The easiest way to do this is to shallow your angle of attack with your irons (i.e., make contact with the ball closer to the bottom of your swing arc), and learn to hit up on the ball a few degrees with your driver. These adjustments negate the need to make radical changes to your swing direction. Basically, all you'll need to do is swing your irons 4 to 5 yards to the left of the target line for every 100 yards the shot needs to travel, and the opposite (10 to 15 yards to the right) with your driver. "Although it can be difficult to get these numbers exact without the help of a TrackMan unit," Manzella adds, "the following drills will help you swing your irons and driver in a way that will significantly improve your contact, accuracy and performance."

A mistake players make when swinging their driver is opening their hips to the target line too early. This forces the club to swing outside-in and strike the ball with a descending blow — the exact opposite of what TrackMan advises.

To fix this error, place your driver between your legs so that the shaft sits against your right thigh. Swing to the top and hold the shaft gently against your thigh with your right palm. Now swing your arms down and shift your weight while keeping your hips closed. If you do it right the grip should push your right palm only a bit. If you do it incorrectly and allow your hips to open too much, the shaft will move way outside the target line.

To hit solid, straight iron shots, you need to hit the ball with a descending blow and swing slightly left of the target. It sounds doable, but the problem is that many amateurs move the club either below the proper plane, which makes the swing too flat and to the right, or over the plane, which makes the swing too steep and too outside-in. For a straight shot, trace a line slightly left of the target line as you swing through impact and beyond. Here's how:

Extend your arms and address a ball without a club. Point your right index finger at a spot just outside the target line behind the ball, and point your left index finger in the opposite direction. From this position, make a mock swing while tracing the line with your right index finger all the way to the ball and beyond (it should feel as though you're skipping a rock in slow motion). Repeat this move until you can trace the correct line with your finger every time, then use a club. If you can trace the line with your clubhead like you did with your finger, you'll hit straight irons all day.

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