The Pro Shop

Gear Talk: Hunter Hines, Part Two

Friday, October 19, 2012 /by

Following Dunlop’s fall racquet launch this past Monday, I sat down with Hunter Hines, the company’s Director of Marketing and Product Development. We discussed two of Dunlop’s new racquet technologies, Aeroskin Cx and Biofiber; we also dug into the topic of carbon layups and their effects on feedback and feel. (To read part one of our conversation, on ways in which Dunlop has sought to improve upon its frame geometry and grommet system, click here.)

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Justin diFeliciantonio: We already spoke about the True Oval head shapes, as well as the new Cx and MoS2 grommets. What other technologies is Dunlop releasing this fall?

Hunter Hines: Well first, we’re debuting a re-engineered version of Aeroskin. It’s called Aeroskin Cx. [Note: Aeroskin is a surface–frame application that, according to Dunlop, mimics the aerodynamic patterning of sharkskin to allow for more racquet-head speed.] The original Aeroskin is a series of dimples on the racquet. It makes for a very constant pattern. But when you look closely at microscopic views of sharkskin—which is what inspired us to create Aeroskin to begin with—you can make out a distinct pattern, one that’s of variable shape and size, depending on where you look on the shark. So with Aeroskin Cx, we were able to drill down and mimic that pattern. What we found is that it’s more aerodynamic than original Aeroskin, and of course much more aerodynamic than racquets without the patterning.

JD: How much more aerodynamic is Aeroskin Cx?

HH: There’s a 36 percent reduction in drag compared to a racquet without Aeroskin, and an 11 percent reduction compared to original Aeroskin.

JD: How do you arrive at those numbers? Again, through wind tunnel testing?

HH: Exactly. We test the racquets not only at different angles, as I mentioned earlier, but also against different wind speeds—anywhere from five to forty meters per second.

JD: Why different speeds?

HH: Because we wanted to see the degree to which Aeroskin Cx would benefit players with different types of swings. Say, for example, we found that the pattern wasn’t offering any aerodynamic benefits at slow swing speeds, then we’d want to, one, go back to the drawing board for that racquet and, two, enhance its skin to better help that type of player.

JD: Out of all the testing you’ve done, whom would you say the Aeroskin helps the most? An advanced player who already has quick swings? Or someone who’s still developing their game?

HH: There are obviously reductions in drag for all player types. But looking at the data, it appears really to most help players with average swing speeds—not really quick, but not very slow, either. To be completely honest with you, to explain the hard science of it, I’d have to defer to our technical designer in the U.K. When we start getting into the finer details of Reynolds numbers and so forth, it goes a little bit over my head.

JD: The one thing I noticed, when I looked at one of your sample racquets, is that the Aeroskin isn’t applied all over the frame. Why is that?

HH: That’s a big question we get asked a lot: If Aeroskin is so efficient at reducing drag, why not cover the whole racquet with it? In fact, we did try that. We tested various degrees of coverage, from five percent all the way up to 100 percent. And what we’ve found is that 30 percent coverage is where diminishing returns start to kick in. Approaching 30 percent, the Aeroskin isn’t as efficient as it could be. But when you exceed 30 percent coverage, it actually starts working negatively on itself: The reduction of drag in one area begins to create an increase in drag in another.

JD: In addition to Aeroskin, are there any other technologies that are launching with the racquets?

HH: One we haven’t talked about is called Biofiber. It’s a pretty cool material that’s extracted from the stem skin of plants. It’s a very fine, hair-like plant fiber; it’s very strong and very light, but at the same time is soft and pliable. We tested a number of different natural fibers in the graphite layups—all kinds of things from flax to hemp to bamboo—and we found that the Biofiber performed the best. It’s very good at distributing shock and removing unwanted frequencies upon impact—by about 18 percent, actually, versus a racquet without Biofiber.

JD: Was there a vibration-dampening technology in the previous generation of Dunlop racquets?

HH: Yes, there was. In the past, we used a technology called HM6, which was a honeycomb-shaped, carbon layup in the throat of these racquets. And Biofiber is actually 80 percent better than that, as HM6 was 10 percent more efficient at taking out vibrations than a standard carbon racquet.

JD: What do you mean by standard carbon? When testing the effectiveness of new technologies, what’s the nature of your control racquet?

HH: My supposition is that it’d be a carbon racquet with a standard, UDPP layup. Most racquets out there on the market, that’s what they are.

JD: UDPP?

HH: UDPP refers to a particular type of graphite layup, which forms the frame. It’s basically graphite laid in one direction—as opposed to, say, a braided layup, where the graphite strands are woven together. When it comes to frame construction, it’s really an infinitely variable situation. There are loads of ways you can change how a racquet performs. Just on a superficial level, a racquet’s graphite can be UDPP, braided, or angled. And you can combine the different layups together. Over time, we’ve collected some very good data on what layups and constructions are best, based on a racquet’s shape and its specifications. And we test those, refine them from there, test them again, potentially refine them from there again, and out comes the finished product.

JD: So say you took the F3.0 Tour, for example, a head-light racquet, 11.5 ounces. And you had one fabricated entirely in UDPP fashion, and another made with a mixture of UDPP and braiding. All else being equal, how would those two racquets play differently?

HH: It’s very difficult to say. We have tested it that way; we always do. But in terms of a larger sample, it really comes down to averages. Some people may feel like the UDPP gives them a cleaner sensation hitting the ball, whereas the braided provides more of a softer, muted feel. But then again, the next person in the testing pool could describe a feeling that’s completely opposite. At the end of the day, we attempt to design racquets that feel good to as large a percentage of the population as we can.

JD: Or, I suppose, the population that will be using that particular racquet?

HH: That’s true to a degree. But we also test racquets outside the population. We have a very good idea of what player and swing type each of these racquets is designed for. But at the same time, there’s always going to be a fair percentage of the population that plays with a racquet that’s not designed for them. So we attempt, as much as we can, to cover the entire board.

JD: But ultimately you’re saying that graphite layups have a lot to do with a racquet’s feedback, and the way different players perceive feedback is not uniform.

HH: Exactly. It’s the same with string. If there’s a string you really, really like, and I try it—I may like it as well, but for different reasons, or I may hate it for the same reason that you liked it. It comes down to a lot of personal preferences. So the challenge is to take those preferences and align them in such a way that you can make sense out of them and build a better racquet for a target player type.

JD: I guess more generally, what do you think accounts for players’ divergent opinions on feedback intensity and feel? Why do you think, for example, one player might say a UDPP layup feels clean, while another says it feels harsh?

HH: That’s a very good question, and it’s not one that’s very easy to explain. I can’t tell you why someone feels the way they do. But what we’ve found is that when your test pool is large enough, the patterns versus the aberrations will eventually show themselves. That’s one thing that’s interesting about tennis players: A lot of people are very, very good at saying, here’s what I feel. It’s easy for them to verbalize that they like something or they don’t like something. But often, it’s very difficult for the same people to verbalize why they don’t like something, or how they would like it to feel differently. Like I said, over time, we’ve collected quite a bit of data on what in a given circumstance will generally work, and what may not work. So in a racquet’s initial testing, we generally have an idea of the adjustments we need to make. But there are always wildcards.

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