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March 17, 2014

APL Team Helps Skier in Paralympic Quest


Alan Ravitz with nurse Rhonda Wyskiel
Alan Ravitz with nurse Rhonda Wyskiel
Top: Lt. Cmdr. Dan Cnossen—in the APL-built sit-ski—on his way to winning a 10-kilometer race at the 2014 U.S. Paralympics Nordic Skiing Nationals in Midway, Utah.
Credit: FasterSkier.com

Bottom: Paralympic skier and biathlete Lt. Cmdr. Dan Cnossen (center) discusses the ideal fit and weight of his new sit-ski with APL's Courtney Moran (left) and Bob Matteson, both of the Research and Exploratory Development Department.
Credit: JHU/APL

For more than 70 years, APL engineers and scientists have applied their knowledge and expertise to tackle critical technological challenges facing the U.S. Navy and our nation. Recently, however, an APL team was given an opportunity to lend those considerable skills and talents to help an individual member of the Navy tackle a personal challenge, and it was an opportunity they willingly accepted.

The sailor involved is Lt. Cmdr. Dan Cnossen, a Navy SEAL who lost his legs to an improvised explosive device in Afghanistan in 2009. During his recovery from the injury, Cnossen began sit-skiing, and he quickly took to the sport. A sit-ski is a specially adapted platform that interfaces directly with standard skis and bindings, making it more accessible for skiers with disabilities.

As his skills grew, Cnossen began thinking about competing in the 2014 Paralympic Winter Games in Sochi, Russia. However, he didn’t think he would be competitive unless he were able to shave a few pounds from his 11.5-pound sit-ski.

“When I was visiting Dan last year in Winter Park [Colorado], where he was training for the Paralympics, he mentioned that the weight of his sit-ski was hurting his chances of being competitive in Sochi,” said Brian Ray, a project manager at APL. Ray was a college roommate of Cnossen’s at the U.S. Naval Academy.

After checking with APL management, Ray contacted APL’s fabrication and composites experts and arranged for Cnossen to visit.

“We immediately wanted to help him, but we also saw this as a chance for us to try some radical manufacturing techniques that would have immediate benefit to many of our sponsors,” said Bob Matteson, of APL’s Advanced Mechanical Fabrication Group.

Engineers John Marks and Joe Hrivnak used 3-D scanner data generated by Matteson’s team to create a computer model of the sit-ski Cnossen had been using, and used those images to “reverse engineer” the device.

“The sit-ski had a metal frame with carbon fiber composition parts on top,” Marks said. “After a structural analysis of his current sit-ski, we decided to use titanium where the current device used aluminum extrusions. We went over every single component of that sit-ski to look for ways to knock mass off of every part we could.”

Dan Cnossen competed in six events at the 2014 Paralympic Winter Games in Sochi, Russia; his highest finish was sixth place in the men’s 1-kilometer cross-country skiing sprint. Click here to see Cnossen’s individual results.

Then they called in prosthetist Courtney Moran to examine Cnossen’s current sit-ski socket setup, his walking prostheses, and the new, lightweight socket setup.

“The sit-ski is very different than his walking prostheses and had different requirements for his control of it,” she explained. “We talked through what type of force he put on the sockets and the areas he felt pressure on each of his limbs during the multiple phases of his ski and pole ‘skate glide.’ This enabled the team to identify areas where the new sockets and seat could be cut back further or made compliant and flexible, so that Dan would have the least weight with the most comfort and control while he was racing.”

Cnossen was hoping to shed a pound or two from his original device; but thanks in large part to the composite expertise and innovative approach of Zachary Ulbig and Will Setzler, Matteson’s team delivered one that weighed about 6.5 pounds—nearly half the weight of the original. Cnossen went on to win several significant races with that newly engineered sit-ski, including three first-place finishes in the U.S. Paralympics Nordic Skiing National Championships in January.

Matteson’s team is eager to apply what it learned to help APL’s sponsors. “Some of the manufacturing processes that were used to make Dan’s sit-ski are aimed at dramatically reducing production time and cost,” Matteson explained. “We took a high-risk, low-cost approach toward developing a fabrication process, which was just what was needed to get a working sit-ski to Dan. As a result, we learned a lot and have already begun implementing some of these lessons into sponsor work.”

“APL has invested heavily in developing technologies to protect warfighters from blast injuries and restore capabilities when they’ve been injured,” said Sezin Palmer, a senior leader in the Research and Exploratory Development Department at APL. “Although we don’t typically do these types of ‘one-offs,’ working with Dan provided us an opportunity to apply our unique design and fabrication capabilities to help a decorated wounded warrior and also develop techniques that apply to sponsor needs.”

Matteson and Timothy Schniepp will present a paper on this effort in June at the Society of Manufacturing Engineers’ RAPID Conference in Detroit.

The 2014 Paralympic Winter Games ran from March 6 to 16.

Read more about Dan Cnossen and other U.S. paralympians from the 2014 games in this New York Times article, “Paralympics, at Peace as Wars Wind Down.”

Media contact: Paulette Campbell, 240-228-6792, Paulette.Campbell@jhuapl.edu