This article appeared in the 2014 Winter issue of LINKS.
Sir isaac newton was sitting under an apple tree, or so the story goes, when he was bonked on the noggin by a falling fruit, leading to his theory of gravity in the 1680s. The first clubhouse in America at St. Andrew’s in New York 200 years later was an apple tree. Coincidence? Perhaps. But the physics of the meeting of club and ball are undeniable. The question these days, however, is just where the center of gravity (CG) in a golf club should be located. For years, the common notion has been that positioning the CG deep (low and back) in a driver is the way to produce a high launch and high moment of inertia (MOI or forgiveness). But that combination also can produce a lot of spin, which reduces distance.
With its introduction of the SLDR last year, TaylorMade made a fairly radical departure, moving the CG much farther forward (toward the clubface) to reduce spin while increasing ball speed. The same characteristics mark its newest driver, JetSpeed. “We’ve been moving weight around since R7, trying to understand what happens in the club,” says Brian Bazzel, the company’s product creation manager. “When the USGA created the rule on MOI limit in 2006, the whole industry sort of chased it, but we now understand that anything past even 70 percent of the limit is a little bit of a point of diminishing returns.”
Another advantage of setting the CG forward and low is that it expands the sweet spot to just below the face’s equator, which is where most golfers actually make contact with the ball, says Bazzel. But to take advantage of the new design, golfers need to increase driver loft by at least a degree or two to get the desired high launch/low spin combination, hence TaylorMade’s new ad campaign to “Loft Up.”
Of course, other equipment companies have different opinions on the optimal CG location, which is a good thing for golfers because it provides more options in the marketplace. At Ping, for example, the feeling is that moving CG forward reduces ball speed on off-center hits, as well as creates more of a glancing blow because of the higher static loft needed. So the company is sticking with a deep and low CG, which also translates into more dynamic loft at impact.
“That’s what everyone’s trying to do from a teaching standpoint and that’s what we’re trying to do from a club design standpoint, turn the static loft at address into more dynamic loft at impact,” says Marty Jertson, Ping’s director of product development. “In other words, a 10-degree driver can turn into 13 or 14 degrees of loft at impact.”
Ping’s new i25 driver has a deep, back CG but is still the company’s second lowest-spinning driver after the Anser due to strategically placed tungsten weights. “The challenge is to design a driver with the CG proportionally low back [for the best combination of MOI and spin] and that’s a hard thing to do, especially with bulky hosel designs and adjustable components that move the CG closer to the face,” says Jertson. “The CG-forward drivers that are in the marketplace have substantially higher CG than on our drivers. Forward CG will reduce spin but at what sacrifice? That’s the advantage of the i25. It gives you low spin, but when you start mishitting it around the face, you’re going to maintain the launch conditions.”
Callaway isn’t really buying into the forward-CG trend either, but its new Big Bertha Alpha does allow golfers to change the height of the CG for the first time in a driver. “If you move the CG too far forward and/or too low it can make the driver difficult to get up in the air and not very forgiving for many golfers,” says Luke Williams, senior director, global woods and irons. “Typically only higher head speed/higher spin players benefit from such a set up.”
The gravity of the situation is the situation of gravity: Moving it around can affect your driving, so don’t be afraid to experiment like Newton did.