The international swimming federation FINA outlawed full-body, impermeable suits in 2009, but Speedo’s Fastskin3 suits use different, still-legal techniques to improve performance:
They started at the top. “The cap and goggles are the first things that hit the water, so they can create turbulence downstream in a way that affects the performance of the suit,” said Santry.
The scientists scanned athletes to produce a three-dimensional, digital avatar. They then manipulated various parts of it — squeezing here, filling in there — and used computational fluid dynamics to calculate how each change altered drag “until we found a theoretically perfect body form.”
Take the cap. The standard model is a plain silicone bowl that wrinkles at the top. Those wrinkles, like any protuberance, create drag. But shaping a cap to the average human head shape — determined by the 3D head-scanning — minimizes wrinkles.
The new cap also has room to pack hair at the nape. That fills what is otherwise a dip between the head and the back. “That dip creates a pressure drag,” explained Santry: a region of lower pressure that ever-so-slightly sucks the swimmer backward. Packing the hair into the gap decreases that drag 3.4 percent compared to standard silicone caps.
The most hydrodynamic goggles shape — a full-face mask reminiscent of Batman’s — violates FINA rules. But the runner-up takes the water flowing over the head to the eye sockets and basically attaches that flow to the face, creating an ultra-smooth “boundary layer” of water.
Smoothness is key. Boundary layers naturally flow toward regions of low pressure, which can split up the layers and create turbulence, increasing drag. The optimal goggle design is shaped like a water droplet and turned up at the temples. “It’s unlike anything on the market,” said Santry.
The goggles cut drag 2.2 percent versus other Speedo models.
The suit redesign addressed the fact that 80 percent of the drag on swimmers comes from their shape. That meant compressing fleshy areas like the thighs, rear end and, for women, the chest, all with Lycra panels sewn into the suit.
While other suits absorb water, Fastskin3 repels it. Less weight from the suit means each stroke propels a swimmer farther. So after four years and 55,000 hours of research and testing, the complete outfit reduces drag by 16.6 percent compared to standard gear, Speedo says.
That translates into an approximately .11 percent potential increase in speed. Not huge, but then the difference between winning gold and silver can be thousandths of a second. At Beijing, American Michael Phelps finished 0.01 second ahead of Serbia’s Milorad Cavic in the 100 meter butterfly. Phelps will be wearing Fastskin3, as will team mate Tyler Clary and Britain’s Rebecca Adlington./blockquote>