Talking heads

Golf International: Callaway's new driver range is notable for moving away from the radical square shapes which you first pioneered back in 2006, towards the more triangular shape of the FT-iZ?
Dr. Alan Hocknell: We've done a lot of new research into aerodynamics over the last couple of years and found that many 'large platform', 460cc drivers – of various shapes – are inefficient in the way they move through the air in terms of the excess drag they generate. This slows them down and compromises distance. In designing the new geometric shapes both for the Fusion and the Diablo 2010 ranges we found we could reduce this drag factor by over 10% and improve clubhead speed by at least 1mph for the same swing energy. This in turn translates into an extra 1.5mph in ballspeed and some 4 or 5 more yards for drives with a decent trajectory.

Gi: Have you therefore moved away from the priority of Moment Of Inertia (resistance to twisting) in favour of this greater focus on aerodynamics and distance?
AH: The triangular shape of the new FT-iZ actually has even higher inertia than the square-shaped FT-iQ. But this is largely down to a new Polar weighting concept we have developed which concentrates approximately 70% of the weight of the head in both the face and the rear, separated by the greatest distance possible allowed under the Rules. We found that this ability to move weight further away from the centre of the club is the secret to increasing the MOI; and, accordingly, both the front-to-back and heel-to-toe measurement is actually larger in the new FT-iZ than the square FT-iQ model.

Gi: Does this mean that square drivers – if they have now been technically superceded – are now a thing of the past?
AH: I wouldn't say they are gone forever. It's a bit like Formula 1 racing, where the cars change in shape and size from season to season in order to get the maximum performance out of the rules at that time. In this case, our 2010 drivers get closer to the limits of the equipment rules and use aerodynamic principles that are not as tightly regulated by the rules as some other performance features.

Gi: Back with the Moment of Inertia buzz phrase, would you accept that a high MOI only improves accuracy for off-centre hits if the golfer squares the clubface at impact – which many of us don't?
AH: It is true that, even with the highest MOI drivers, if you are pointing the face of in the wrong direction at impact the ball will at least start off in that direction. But we have also done a lot of work on the bulge and roll radius of our drivers to have them compatible with the position of the centre of gravity. This does provide some corrective capabilities: for example, a shot hit off the toe can enjoy some opposing spin to limit the effect of a slice.

We don't ignore the fact that many golfers don't square the face at impact; and a well-designed modern driver doesn't hit the ball purely in straight lines.

Gi: As a scientist, are you always battling against trade-offs inherent in driver design – for example the pros and cons of longer shafts and heavier heads?
AH: Driver design does involve performance trade-offs between many variables. That's part of the constant challenge of optimizing both an individual driver and a range of drivers. But as well as the scientific trade-offs, we have to think also of the types of players we are designing for, their physical abilities, their swingspeeds and clubheads speeds, and what happens when they hit good and bad shots. It's a combination of these factors that helps us come up with designs to suit the greatest number of players.

Gi: And aesthetics are obviously very important. For example, your new Callaway Diablo Edge driver has a very distinctive shape. How much of that is down to styling and how much to a genuine performance rationale?
AH: The pointed feature on the rear of the head of the Diablo Edge is purely for aesthetics. But it is part of a heavily tapered body that allows us to stretch the head back from the face to the rear (for the reasons mentioned earlier) but while staying within the 460cc volume limit.

Gi: What do you feel about the trend in the driver market towards drivers with increasingly lighter overall weights – some now well below 300 grammes – with claims of ever faster swing speeds?
AH: There is a lot of research to be done still on the optimum weight for drivers – and for each model of driver as there are so many different types of player. We have our own data that we've collected from golfers playing our prototypes with everything from lightweight heads with long shafts to heavy heads with short shafts. But, so far, we've found that there isn't a very significant difference in performance for the majority of golfers.

Of course, on an individual basis, there are some golfers who can generate more clubhead speed from a lighter weight club, just as there are some strong golfers who can handle a heavier head for more distance and also more control. We are not prescribing one solution, such as 'long and light', and saying it is good for everybody. I don't think it is.

Gi: How much has the use of exotic materials beyond titanium transformed the design opportunities for golf R&D scientists?
AH: Massively, for us at least. In an all-titanium driver you need a significant amount of the total weight – some 45% – just to hold the head together before you start concentrating mass around the head for performance reasons. But in one of our Fusion drivers, which fuses lightweight graphite with titanium, this central body mass is barely 20% of the total weight. You then have the remaining 80% of the weight 'budget' to use in creative ways to provide direct performance advantages. In an all-titanium head that weight is trapped – you can't do anything useful with it.

Ideally, you want command over a range of materials. Our FT-iZ driver has a titanium face, a carbon-fibre body, an aluminium 'skin plate' and a steel weight in the back. All these materials are chosen for a very particular purpose to optimize every last gramme.

Gi: But there is still a large market for all-titanium models. Is that down mainly to the cost factor?
AH: Certainly it is available at a price point where more people are ready to pay. And it has a certain cachet in the golf market. We are definitely not turning our back on all titanium technology but we have focused on refining our manufacturing methods. The new Diablo Edge driver, for example, features a different construction process to the casting process typically still used in the industry. We now use whole sheets of titanium that are pressed in a very precise way into the shapes we need for the body. This is much more efficient in terms of allowing much thinner walls, more accurate weighting and reduced levels of waste. It's actually similar to the way we make the Fusion drivers, so we are transferring our high-end techniques across different ranges.

Gi: How do you approach the issue of driver 'acoustics'? The sound at impact is an important element of feel when choosing a driver – and yet it is so subjective?
AH: It is crucial parameter for the designer – although it is indeed subjective and there is a wide variety of opinions. It is crucial because golfers trying a new driver for the first time won't necessarily know immediately whether it is longer or straighter than another one – but within two or three shots they will quickly develop an opinion on the club from the look and the sound. These are thing they can judge whether they are a good golfer or a bad golfer.

Gi: Presumably there is wide variation in sound according to material – for example, there is a perception that graphite sounds 'dead'?
AH: There was, but that is no longer the case, at least not with our clubs. We have done a lot of research into golfers' reactions to impact sound, in terms of the pitch frequency, duration and loudness, both with our clubs and several of our competitors under test conditions. As a result, we have tried to work out what are the characteristics of sounds widely acknowledged as “good” versus those regarded as “bad”. We then steer the sound of a new design into the right part of the chart for these three parameters. Before even making a prototype we will simulate the expected sound and see where it plots. You can definitely say our new drivers are 'sound engineered'!

Gi: The Diablo Edge Tour driver is notable for sporting a full length hosel – somewhat surprising given the Big Bertha tradition of eliminating the hosel to make better use of the weight?
AH: It's a change but we're proud of it. It shows that we are extending the range. The version with the hosel is intended for more advanced players, those who want to hit the ball a little lower with higher head speeds. But there is a standard model, too, for average players.

We do have different features on different models but we stress that the same basic benefits are being derived from the underlying technology – it's merely being optimized for individual player types. It's the same with the Fusion range: Phil Mickelson and Ernie Els are using Fusion technology on tour, but in a specification that's suited to their high swing speeds and the workability they demand. But that same Fusion technology is available in an FT-iZ driver in a 13-degree, high-trajectory model with a light flex shaft for an average golfer.

It's the same in other sports – the tennis rackets that you see in use at professional Tour events aren't quite the same ones you buy 'off the shelf', but they use the same technology.

Gi: How much does working closely with top tour pros help in the overall design process for drivers?
AH: It shows us the huge number of ways in which we can alter the performance characteristics of golf clubs. And it gives us a full command of them when making even very small adjustments in ball flight. When someone like Alvaro Quiros demands very subtle changes in his trajectory we know exactly how to deliver that very predictably – rather than resorting to trial-and-error which is very frustrating for the player and the technician. A lot of this is down to the way we can simulate performance on a computer, but the feedback from the pro tour refines this process further and improves the design stage for all drivers in the range.

Gi: Are all today's top players highly technical when it comes to optimising their distance and accuracy?
AH: They differ. Someone like Phil Mickelson is all about feel around the greens but with the driver he is very much 'by the numbers'. He will often be able to call out the backspin on one of his drives to within 100rpm. Ernie Els doesn't bother as much with the numbers, he is mainly concerned with a visual representation of his ball flight. We see a lot of Phil as he's based in San Diego and he's always tinkering around with innovative ideas.

Gi: Like the prototype hybrid you designed for him for the 2009 US Open?
AH: Phil came to us with a specific set of concerns about hitting hybrids. He wanted the distance from the rough to be equal to the distance of an iron from the fairway or the tee. Plus he wanted to hit a greater variety of creative escape shots from 'trouble'.We made him a unique, smaller hybrid head featuring a C-grind sole more associated with a wedge to relieve the turf interaction on both heel and toe. He was able to use it very successfully from a variety of different lies in the rough.

Gi: The marketing and buzzwords associated with premium driver designs reaches new levels every season. But how important is it for average golfers to understand the concepts when choosing a driver – rather than just going to get properly custom fitted?
AH: Everybody should certainly try a driver before they buy it, and custom fitting is a highly recommended step. But we develop clubs with different amounts of technology to suit different price points. If a golfer can reach to the higher price they will definitely gain an advantage from the technology. It may not be immediately obvious with their best shots, but it will be with their mishits – which is most of us, most of the time!

For golfers choosing Callaway, I would recommend the FT series and, if they can't quite reach to that, then the Diablo Edge and Edge Tour or our other clubs at the titanium price point. I genuinely feel we have designed clubs for all player types.

Gi: Has that R&A's and USGA's tighter restrictions on things like head size, Coefficient Of Restitution and Moment Of Inertia, boxed you into a corner – or do you thrive on the challenge of finding new ways to improve performance within ever tighter boundaries?
AH: It would certainly be easy to moan and say that all avenues of innovation have been closed down. But, in a way, it makes you hungrier. And for a company such as ours with a large R&D investment think it may actually be an advantage as we have the ability to study in great detail the areas that aren't governed by the rules – at least not yet!

One area is the aerodynamics of the head. There are no limits on drag coefficients, for example. Our competitors will, of course, say similar things but we have discovered that this area is very complicated. It's easy to draw pictures with airflow arrows just as they do in car commercials – but a golf club accelerates from 60 to 100mph in the space of a couple of feet while also rotating through 90 degrees and changing direction. This is complex stuff that is still in its infancy and our 2010 line is the first to benefit from any of that work.

Gi: You have been behind some highly elaborate innovations, like the i-Mix interchangeable clubhead and shaft system. Even though it is for a very small portion of the market, how important is it for Callaway to be seen as a pioneer of radical technology?
AH: I think it's good that, every once in while, we make a clear visual and technical statement that we are leaders in innovation. i-Mix is one example – though as well as being a commercially available product its original use was as an advanced fitting tool for our custom fitters.

I accept that we haven't seen many regular golfers pick up on the potential benefits of having more than one clubhead or shaft, but being the first to do anything is consistent with our mantra of innovation that made the company famous. We will certainly continue to 'push the envelope'.