THE MUDBALL STUDY…How dirt impacts the shape of your shots

Blog, News

Author: Keri Schmit

The U.S. Open is confusing and confounding enough. Now enter golf’s version of Russian roulette known as the mud ball.
You piped your drive down the fairway, but your ball picked up a clump of mud along the way—a common occurrence in soft conditions. Barring a local rule that lets you lift and clean the ball, you’ll have to play it as it lies and deal with the dirt.
Mud on a ball can have a significant effect on trajectory, distance and in-flight curvature.
The trouble is no one can really predict what that effect just might be. Nobody’s quite sure.
Rock Ishii, director of golf ball research and development at Nike, has studied the mud ball conundrum for years. He has some specific answers, but concedes, “It all depends on how much mud is on the ball,” he says, indicating the distance loss on a 200-yard shot might be as much as eight yards and that if there’s mud on top of the ball a shot will tend to spin too much and balloon up in the air.
He also believes the ball will curve in the opposite direction of the side of the ball the mud is on. “That’s the basic tendency, but if there is too much mud, the ball starts going the same direction as the side the mud gets on. We don’t have enough knowledge what amount of mud turns it to the opposite.”
The main problem with the physics of a mud ball is that there are so many variables, and several of these variables conflict with each other.
As John Axe, a Ph.D., member of the Golf Digest Hot List Technical Panel, former associate director of the Brookhaven National Laboratory and a former golf ball research scientist, explains, “I’m not surprised that people cannot agree upon a single answer.”

Here are the issues:
First, if the mud gathers on only one side of the ball it will slightly change the ball’s center of gravity toward that side (assuming the ball lies flat on the ground with the mud only on one side), making it off-center compared to a clean ball or, more simply, lop-sided. That off-center effect means the ball is going to rotate and curve in the direction of where the extra weight is, all things being equal.
It has to do with how the air flows around the ball as it flies through the air. In a perfectly struck shot the mud would stay on one side and the air would flow more unsteadily around the mud side and more cleanly around the non-mud side, causing to the ball’s flight to drift toward the non-mud side.
Deciding how a muddy ball will affect your shot’s trajectory has always been a guessing game. Traditionally, it’s been assumed that as the ball flies, the mud creates air resistance—or drag—that sends the shot in the direction of the ball’s soiled side. So mud on the ball’s left quadrant, for example, would tug the ball to the left. But there’s never been compelling data to confirm or refute this assumption—until now.

Keiser University golf staff in West Palm Beach, FL helped conduct an experiment using TrackMan to analyze 400 “muddy” 6-iron shots hit by 10 single-digit-handicappers.
They used weighted lead tape to simulate a 1.9-gram chunk of dirt (a bit less than the width of your thumb) clinging to various locations near the ball’s equator. They then compared these 400 swings with some mud-free base swings, and then tallied the results.
Contrary to conventional wisdom, every single “muddy” ball curved in the opposite direction of the sphere’s dirty side (results, right). It’s clearly time to rethink our assumptions about mud’s effect on ball flight.

Tips on how to hit a mudball according to Tiger Woods:

• Ball Sitting in Mud
Mudballs should be hit with an easy swing to avoid creating excessive spin; you must also adjust your aim to account for a ball that is mud-caked on one side. Swing Surgeon suggests using less loft and hitting the ball low as an additional way to avoid spin. According to Woods, your best bet is the “half inch” approach: choke up on your club half an inch more than usual, with the ball back a half inch further than normal. The power should be generated from your shoulders, with a quiet lower body and feet firmly planted on the ground. A sweeping backswing and standard follow through is the final step in making the best of this situation.
• Ball Stuck in Mud
A ball stuck in the mud must be approached differently from one that is merely muddy, or sitting in a muddy lie. To increase your chances of successfully dislodging the ball, use a pitching wedge or a 9-iron. Begin with an open stance and the ball moved back past the middle of the stance. Use a firm grip and swing across the foot line with a downward approach to free the ball and send it forward toward your target. Although the sand wedge may seem a logical choice for this shot, you should forego it due to the risk of the club digging into the ground.
Here are some more takeaways to keep in mind, based on the study:
• If the clump of mud or dirt is smaller than the width of your thumb, it will tend to make the ball fade when it’s on the left side of the ball and draw when it’s on the right side.
• If the hunk of mud is wider than your thumb, the volume is likely large enough to curve the shot in the direction of the ball’s muddy side, in keeping with the old rule of thumb.
• Club up! Our testers lost an average of 5.3 yards on mud-ball shots.
• The farther the mud is from the clubface/ball contact point, the more it will curve.