The Speedo LZR Racer is shaping up to be the must-have accessory for record setting swimmers. Yesterday at the U.S. Olympic Trials, two more swimmers turned in best-in-the-world performances while clad in the high-tech swimsuit. Michael Phelps lowered his own world record in the Men's 400m individual medley, while Katie Hoff set a new World Record in the Women's 400m individual medley. In all, 40 world records have now been set by swimmers wearing LZR Racer since its debut in February. Read about the engineering behind the world's fastest swimsuit here.
In competitive swimming, where hundredths of a second can separate winners from losers, hydrodynamic drag really is a drag. So the world’s top swimmers now take to the water in drag-reducing suits that cover more skin, leaving the skimpy swimsuits to the sunbathers. Speedo yesterday launched the latest of these sleek racing suits, the FASTSKIN LZR Racer.
Speedo made a splash with its first FASTSKIN swimwear at the 2000 Summer Olympics. Made from a knitted biomemetic fabric designed to emulate the hydrodynamic characteristics of shark skin, these suits were worn in 80 percent of Sydney’s medal-winning performances. The technology in the LZR Racer, which will be worn by members of the U.S. Swim Team in the upcoming Beijing Olympics, makes FASTSKIN even faster.
“We believe the LZR Racer truly is the world’s fastest swimsuit,” says Jason Rance, head of Aqualab, Speedo’s R&D group. And the company’s extensive testing of the new suit backs up that claim. In flume tests conducted at New Zealand’s University of Otago during the development process, the LZR Racer offered a five-percent reduction in passive drag compared to the FASTSKIN FS-Pro suit that debuted last year and has since been worn in more than 20 world-record performances. The same tests showed the suit produces ten percent less passive drag than the FASTSKIN FSII suit that came out in 2004, and Rance adds the suit has about 38 percent less drag than ordinary Lycra.
Those drag reductions translate to speed in the pool. Speedo worked with the Australian Institute of Sport to test the LZR Racer in the pool. According to Rance, swimmers saw a four-percent increase in speed when wearing the new suit, compared to runs in their training swimwear. The new suit also contributed to a five-percent improvement in the swimmer’s oxygen utilization versus runs in the training swimwear.
Seven elite U.S. swimmers, current or former world-record holders all, attested to the suit’s speed during a launch event in New York yesterday. Among them was Michael Phelps, who won a record eight medals at the 2004 Summer Olympics in Athens. Phelps says he “literally felt like a rocket coming off the wall” when he first tried the LZR Racer.
It’s no coincidence Phelps brings up rockets when he talks about the suit. The LZR Racer came out of a development program that seemingly has more in common with aerospace engineering than swimwear design. In fact, NASA Langley researchers had a hand in the suit’s development. So did engineers using ANSYS Inc. computational fluid dynamics (CFD) software.
Those engineering efforts paid off in materials and construction breakthroughs that together improved the suit’s ability to help swimmers slice through the water more efficiently.
One of these breakthroughs involves the development of a new low-drag, water-repellent polyurethane membrane. Speedo laminates panels of this low-drag material onto the suit’s base layer at strategic drag-reducing locations. Rance says Speedo looked at about 100 different fabrics before picking the panel material.
NASA Langley’s Fluid Physics and Control Branch helped with that selection process by evaluating the surface roughness of nearly 60 different fabric candidates in its low-speed wind tunnel — operated at 28 m/sec to simulate a swimmer in water moving at 2 m/sec. “We were assessing which fabrics and weaves had the lowest drag,” says Steve Wilkinson, the aerospace engineer who conducted much of that testing. “The tests have generally shown the smoother the fabric, the lower the drag.” In this regard, the new panel fabric represents a departure from the rougher knit used in the original Fastskin suits.
Speedo’s Rance declined to disclose the measured drag values for the membrane material, but both he and Wilkinson say it has a skin-friction drag on par with the flat, smooth aluminum plate that serves as the point of comparison in the wind tunnel tests. “Speedo really nailed it with this material,” Wilkinson says.
The swimsuit material also has another attribute that contributes to the swimsuit’s low passive drag. As Rance explains, both panels and the swimsuit’s woven base material both have better compressive capabilities than the fabrics found in previous Fastskin suits. That attribute helps reduce the form drag associated with the suit — by compressing the swimmer’s body into a better hydrodynamic shape and by minimizing muscle oscillations. As a way to describe the compressive force, which Speedo doesn’t measure directly, Rance notes that stretching the panel material in tensile tests requires 7 kg versus just 100-200 gm for standard swimsuit fabrics. The new base fabric for the LZR Racer likewise provides more compressive power at 1,200 gm versus about 400 for the base material found on previous FASTSKIN suits.
The location of the panels is where ANSYS’s Fluent CFD software entered the picture. Rance explains the software’s predictions of friction and flow around the body helped Speedo identify “drag hot spots” that could benefit from the panels.
Speedo’s CFD work and physical testing focused on passive drag – or the drag produced by the swimmers body while it’s held in a streamlined position. This position, which the swimmer typically assumes for up to 15m after the initial dive or turn, is important. There are opportunities to do even more with CFD in the future to analyze the swimmer throughout the race. Jim Cashman, ANSYS’s president and CEO, says the success looking at passive drag sets the stage for more complex multiphysics simulations as the swimsuits continue to evolve. “For example, we could look at the hydrodynamic pressure on the swimmer’s body moving through the water in conjunction with the structural aspects of the suit,” he says.
Speedo engineers bolstered the fabric’s inherent drag-reducing capabilities with the construction of the suit itself. For one thing, Speedo engineers built in a corset-like section that supports the swimmer’s core. For another, they reduced the effect of seams on drag by getting rid of many seams and making the remaining ones disappear. Rance points out that previous Fastskin suits were composed of as many as 30 different pieces. Speedo creates the LZR Racer from just three pieces, each one a complex 3D pattern. And it now joins those pieces with an ultrasonic welding process that “gives the effect from a drag standpoint of having no seams at all,” Rance says. The LZR Racer is not the first sporting garment to use ultrasonic welding, but Rance says the strength and quality requirements associated with this high-profile application required many engineering hours to dial in a suitable welding process.
All the technology that went into the suit doesn’t come cheap. The LZR Racer’s full bodysuit will sell for $550. But for its intended users, some of whom will compete in Olympics, that’s a small price to pay for some extra speed.