ON THE FAST TRACK
By Susan Keen Flynn
When athletes in the Winter Olympic Games in Sochi, Russia, take center stage February 7-23, so will composites. The Olympics will feature 15 disciplines in seven sports – biathlon, bobsled (which includes skeleton), curling, ice hockey, luge, skating and skiing. And critical apparatus for all the events will incorporate composite materials.
Like the sports themselves, some of the composite applications are media darlings, such as skis and snowboards made from carbon fiber, Kevlar and fiberglass. Others are less heralded. Composite materials provide ankle support in skates for hockey players, short-track athletes and speed skaters. Handles in curling brooms are constructed from carbon fiber to make them stronger and lighter. Some athletes in the biathlon use rifles with barrels wrapped in carbon fiber to reduce weight.
Olympic athletes often lead the charge to adopt new high-performance materials in their quest to shave hundredths of a second off their time in an event or safeguard themselves with protective equipment during crashes or collisions with competitors. The most significant material developments in this year’s Winter Olympics will likely be on display at the Sanki Sliding Center, site of the skeleton, bobsled and luge events. U.S. teams for all three disciplines hope to bring home medals thanks to sleek new sleds.
Customization of Skeleton Sleds
A few years ago Tuffy Latour, the coach of the U.S. skeleton team, contacted Hans deBot of deBotech Inc. to create a custom saddle for racer Katie Uhlaender. The carbon fiber and advanced composite parts manufacturer in Mooresville, N.C., had already produced an aerodynamic carbon fiber pod – the bottom portion of the sled – for the team. Now Latour wanted a saddle, which is affixed to the pod and includes handles, fitted specifically for Uhlaender. (Athletes lie face down on the saddle when they ride down the frozen track.)
deBot worked with supplier BSCI to pour a splash of Uhlaender’s body. “We put her on our surface table in riding position and poured a urethane casting of her body from her chest to hips,” says deBot. “From that, we digitally scanned the splash, modeled it on the computer and cut a pattern and tool to build her saddle.” The carbon fiber saddle was affixed to the pod, which features steel runners on the bottom.
Uhlaender ran the sled at the 2012 World Championship in Lake Placid, N.Y., and won by less than two-tenths of a second. “That provided a lot of motivation in the coaches’ eyes to do more,” says deBot. In preparation for the Sochi Olympics, deBotech has created custom saddles for three men’s skeleton racers as well as a new one for Uhlaender.
Previously, sleds were constructed from wet laminated fiberglass. The new sleds, designed by ProtoStar Engineering and called the ProtoStar V5, are made from a mix of high-modulus and intermediate-modulus carbon fibers. “It’s all prepreg material, resin-optimized for strength-to-weight ratios and vacuum bag molded and autoclave cured,” says deBot. He says that autoclave curing yields the best surface quality and structural integrity.
“We probably have the most technologically-advanced, slickest bullets out there for our U.S. teams now,” says deBot.
Weight Distribution in Bobsleds
deBotech also worked on the Night Train 2 sled for the reigning Olympic champion four-man U.S. bobsled team. He calls the bobsled “a whole different animal” from the skeleton. “It has a lot going on because of the size difference and you’re hauling around four guys,” he says.
deBot got involved with bobsled when a driver of a four-man team approached him to build a sled for the 2002 Winter Olympics in Salt Lake City. “I jumped at the opportunity to support our country and take on a high-profile job,” recalls deBot. He admits he didn’t know anything about bobsled, but figured his experience with clients in NASCAR and other motorsports would guide him. deBot downloaded specifications on the sled’s length, width and minimum weight from the International Bobsleigh & Skeleton Federation.
Like the skeleton, previous bobsleds were made from wet laminated fiberglass. “American athletes were competing with sub-par sleds we were buying out of Europe,” says deBot. deBotech produced a sled made from carbon fiber, Kevlar and other high-modulus materials, but the two-man team did not qualify for the Olympics. However, the team did participate in a trial run in Salt Lake City that caught the attention of Bob Cuneo of Chassis Dynamics and Geoff Bodine, former NASCAR driver and owner of Bo-Dyn Sled Products. Soon after, Cuneo, Bodine and deBot teamed up to build state-of-the-art bobsleds.
The body of the Night Train 2 is constructed completely from composite materials. “It’s built like the monocoque chassis of a race car,” says deBot. “It has very specific layup schedules in the initial cure of all the structural components.” The sled features carbon fibers, carbon/Kevlar® hybrids, high-modulus fibers, unidirectional tapes, Nomex™ honeycomb core and more. This allows deBotech to address high-load areas of the sled locally without increasing the sled’s overall weight.
“Sleds have a minimum weight, but they don’t tell you where to put that weight,” says deBot. “If I can save an enormous amount of weight in the body and still be structurally sound and perform aerodynamically, then all the weight can go on the centerline at the bottom of the sled. That lowers the center of gravity tremendously and increases performance ten-fold.” And that’s an important advantage in a sport that “never lets up,” according to deBot. “You push off the top of the track and the sled is in the hands of highly-trained Olympic athletes and Sir Isaac Newton!”
Stiffness in Luge Runners
The former head coach of the U.S. national luge team, Wolfgang Schaedler, built sleds with a wood core and fiberglass wrap in his garage. “He was a very talented sled builder, but the inconsistency of the hand-built sleds manifested itself in several ways,” says Duncan Kennedy, a three-time Olympian in luge who now serves as technical director of USA Luge. None of the parts were interchangeable, so when something broke it couldn’t be repaired quickly. In addition, because the sleds were one-off items the team couldn’t accurately compare the performance between them.
To remedy this, USA Luge partnered with The Dow Chemical Company in 2007. In 2012, the two launched a program to re-engineer the team’s sleds for the 2014 Winter Olympics, with particular emphasis on upgrading the kuffens – or runners. A team from Dow Materials Science evaluated approximately 20 core materials and resins. “We wanted to go through an extensive evaluation process because we felt [USA Luge] was more or less just taking what they had and sticking with it, making minor changes,” says Jay Tudor, research scientist for Dow Core R & D in Midland, Mich. “We wanted to provide a fresh look.”
The challenge was determining exactly what characteristics the riders needed: Researchers in the lab and athletes who ride the luge on their back down an icy track use a different lingo. “We couldn’t really ask them what modulus or elongation they needed,” says Tudor. “We had to talk in terms of stiffness of the kuffens.” Kennedy provided insight from the athletes’ perspective.
After a lot of discussion and testing, Dow built kuffens made of a mix of materials, including carbon fiber. Athletes tested the sleds in competition during the 2012-2013 season. Though it’s hard to quantify the effect the new kuffens have on performance, Kennedy is cautiously optimistic. “It appears the sleds are at least half a tenth to a tenth-and-a-half [of a second] quicker, which is massive in luge,” he says. And athletes have told Kennedy the sleds are smooth, predictable and easy to drive.
Dow has also begun work on new pods and bridges for the sleds. (Bridges attach the pod to the kuffens.) Both use a mix of materials, including Kevlar®, carbon fiber and fiberglass. “We select the mix to get the right balance of stiffness, flexibility and as much toughness as you can garner in something built to go fast and occasionally collide with an ice wall,” says Scott Burr, lead research and development manager at Dow Core R & D.
To create pods and bridges, Dow’s researchers moved into uncharted territory – low-volume manufacturing. So they used vacuum assisted resin transfer molding (VARTM). “This is a new capability for our group, and we’ve since been able to use it for other projects,” says Tudor. While he would not disclose any specifics, Tudor said VARTM is useful in making new materials and samples for customers.
Dow has provided eight sleds with new kuffens to USA Luge for the Olympics, mostly for singles competition though some double sleds have new components. Kennedy anticipates that at least one sled will feature a new pod, too.
“We’ve taking these elements of a sled that have been a staple for decades and worked with Dow to open the box up and try new ideas,” says Kennedy. “We’re running things on the track that no other country is – and haven’t even thought of. Hopefully we see positive results. But I guarantee we are pushing the envelope. And that’s exciting.”
Susan Keen Flynn is managing editor of Composites Manufacturing magazine. Email comments to firstname.lastname@example.org.