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reprinted from UAH Alumni NEWS UAH engineers stand alone atop the concrete boat-building world after winning an unprecedented fifth American Society of Civil Engineers' concrete canoe national championship in June.
Going into this year's national championship at San Diego State University, UAH and the University of California at Berkeley were tied with four titles each. UAH previously won in 1993, '94, '96 and '98. UAH won the technical design paper, finished second in the canoe "final product" judging and the overall races, third in the trade show display and fifth in the oral presentation. Clemson University finished second. Oklahoma State was third, followed by University Laval of Canada.
UAH used a space-age concrete mix and graphite mesh to make its 76 pound, 22.3-foot canoe, "Survivor." The 24 canoes in the national competition averaged almost 17.5-feet long and about 117 pounds. The unique concrete developed for their canoe has UAH team members and faculty advisors convinced that concrete could be the next space age wonder material. Spaceships made of concrete? It could happen. "There's a really good chance these materials will replace the aerospace composites that are out there now," says UAH's Dr. John Gilbert. "I think we can make structures out of concrete that are lighter and more flexible than structures made of graphite epoxy composites." The UAH concrete could be used to support telescopes in space, for rocket fuselages, to build a lunar colony - or for low-cost emergency shelters on Earth. "A space station wall or space telescope mount made of this might be thicker than graphite composites, but it wouldn't necessarily be heavier," said Gilbert, a team coach and professor of mechanical engineering. "The concrete is the lightest part of the structure. And concrete would be less vulnerable to things like radiation or atomic oxygen erosion." UAH's flexible concrete is the end product of mixing and testing more than 200 combinations of Portland cement, glass microbeads (microscopic hollow spheres), latex, acrylic fortifier and water. The end product is so light that a solid block will float, and so flexible it bends without breaking. Bending is important. UAH's new canoe has no internal struts or supports. Instead, it was designed to bend and flex - to "swim" through the water. Designing a watercraft to flex is a revolutionary proposal. Structures and vehicles are normally designed and reinforced to reduce or eliminate bending and twisting. It's even more revolutionary that the boat's natural harmonic was intentionally lowered, "tuning" the canoe so it reached resonance when raced. In engineering, resonance is almost always thought to be a bad thing. Every object has a natural frequency or wavelength, based on size, shape, density and other physical properties. Matching an object's natural frequency with outside forces, such as sound waves, releases tremendous energy. That's why certain high frequency musical notes can break glass. Perhaps the best example of what happens when a large structure reaches resonance was the first Tacoma Narrows suspension bridge. In late 1940, powerful wind blowing through the bridge cables set up an extremely low frequency hum that matched the bridge's natural frequency. Film of the bridge shaking itself to pieces is still shown around the world. Why design a canoe specifically to do what the Tacoma Narrows bridge did? To capture that energy. A moving boat causes waves, setting up turbulence and causing drag. The boat fights against these forces to move forward. A canoe at resonance might move with the water rather than against it, Gilbert said. Survivor is designed to flex during each paddle stroke, storing energy that is released between stokes. "The boat surges forward and 'swims' between strokes," said Gilbert. The team also found that the boat's flexing gives a unique ride compared to rigid canoes - like the difference between riding a bicycle and riding a camel. "We really had to train it and ourselves," Gilbert said. "We're trying to deal with something as close to a living thing as we've ever had. You have to get used to that in the saddle, so to speak." Return to Main |
