The Loop

Callaway's Great Big Bertha Epic employs unique internal structure for "20 percent thinner face"

January 04, 2017

Callaway’s Great Big Bertha Epic drivers already have Rory McIlroy's attention. And one reason just might be a design theory that's contrary to the conventional wisdom.

It seems nearly everything in driver design over the last two decades has been about increasing flexibility. The new GBB Epic drivers aim to turn that thinking on its head by making the club selectively stiffer.

In simplest terms, Callaway's Great Big Bertha Epic and its low-spinning brother, the Great Big Bertha Epic Sub Zero, have fortified the frame immediately behind the face to concentrate the club’s flexibility there, rather than letting it dissipate across the crown and sole.

Achieving that kind of performance necessitated an internal structure that appears to be as distinct as it is difficult to manufacture. In a technology Callaway’s marketing arm has niftily labeled "Jailbreak," two thin titanium rods immediately behind the face join the crown and sole, essentially framing the center of the face. (That's the image you’ve seen pulsating in the company’s pre-launch hype ads for the new driver.)

Specifically, the engineers at Callaway were focusing on the flexibility of the edges of the crown and sole nearest to the face.

“This structure stiffens the body significantly and allows for greater face loading, greater deflection in the face,” said Evan Gibbs, Callaway’s director of metalwoods research and development. “Because the boundary’s so stiff, the face has to be about 20 percent thinner.”

Making it thinner results in more of the fact being able to deflect at impact, creating a larger area that produces ballspeeds close to center-hit performance.

“It really forced us to change the way we thought about how the face of the driver should be designed, how you really want to optimize the stiffness of the face together with the stiffness of the boundary,” Gibbs said. “It was extremely challenging conceptually to get it to work, but even more challenging physically to get it to work. It was quite an engineering feat as well as a design accomplishment.”


Even as light as the titanium rods are (about three grams each), the design does push some mass forward, which would normally not be ideal for forgiveness. But Callaway attacked that problem by incorporating extensive weight-saving carbon-composite layers in multiple areas in the crown and sole, and leaving titanium as almost a skeleton around which the rest of the driver is built. (It’s a construction technique the company first revealed in its Big Bertha Fusion driver, which was introduced in August.)

This use of carbon composite includes the entire crown and three distinct panels in the sole. The crown is the first in company history to weigh less than 10 grams. Callaway uses two forms of carbon composite, including a new formulation of a triaxial-carbon weave Callaway says is unique to driver design. The triaxial-carbon material is 65 percent lighter than titanium.

By replacing titanium with carbon composite in the sole, heavier material is pushed to the outer perimeter for a driver with a higher stability on off-center hits. That yields better retention of ballspeed and keeps spin levels consistently lower across the face.

The standard GBB Epic features a 17-gram sliding weight, which has been refashioned from its previous iteration in the Great Big Bertha driver. First, it’s seven grams heavier than in last year’s Great Big Bertha, and second, its channel in the rear perimeter is more flush to the sole so the weight stays low for a lower center of gravity. The weight can be shifted to a range of toe and heel-biased positions to counteract draw and fade misses.


The GBB Epic Sub Zero, the driver that McIlroy is expected to put in play next week in South Africa, is a lower-spinning option that features two weight ports in the front and rear portion of the sole to control launch and spin. Putting the heavier, 12-gram weight in the front lowers spin and launch, while putting it in the back port increases launch and adds off-center hit stability. Unlike many other low-spin drivers, Gibbs says it yields a moment of inertia measurement that is among a small group of the most stable heads on the market.

“It’s a very large 460cc forgiving shape, but we’re able to retain all of the low-spin characteristics that you typically see in 440cc clubheads,” Gibbs said. “It’s a very high MOI driver with a very low spin characteristic. That’s why we believe it’s a paradigm shift.”

Both drivers feature Callaway’s eight-way adjustable hosel that allows loft to be tweaked up by as much as two degrees and down by one degree, while independently toggling between standard and upright lie positions. The standard GBB Epic is available in 9-, 10.5 and 13.5-degree lofts, while the GBB Epic Sub Zero comes in only 9- and 10.5-degree heads.


The GBB Epic/Sub Zero line also includes fairway woods. Each features the lightweight triaxial-carbon-composite material for a crown that weighs less than six grams. That helps lower the center of gravity for less spin and higher launch. Both also feature the latest version of Callaway’s cupface that wraps around the crown and sole for improved flexibility. The Sub Zero version incorporates a 22-gram and a three-gram weight that can be switched between front and back ports. Moving the heavier weight results in a backspin change of 250 rpm, Gibbs says.

The standard fairway woods will be available in six lofts. The 14-, 15-, 18- and 20.5-degree models feature the company's eight-way adjustable hosel. The 21- and 24-degree versions will be glued-in hosels. The Sub Zero line will offer three adjustable lofts (13.5, 15, 18).

The GBB Epic/Sub Zero drivers ($500) and fairway woods ($280) will be available Jan. 27.