Using a bicycle, a plastic bag, a fan and pieces of wood, some Centennial High School students have made a human-powered Hovercraft that can carry as many as five passengers a foot above the ground.
The advanced-placement physics class built the contraption as an entry in the Human-powered Hovercraft Competition on Sunday in Wheaton. Centennial High of Ellicott City placed third in the contest, which attracted six high schools from around Maryland.
"It was very tough," said student Alison Chen. "We put in our all."
Centennial's Hovercraft is operated by a cyclist who pedals, powering the fan -- which inflates the plastic bag and lifts the whole craft off the ground. It can float in place indefinitely, depending on the pedal power of its pilot.
The students first wrote for basic instructions through a program sponsored by George Washington University and the U.S. Department of Defense. Then they spent 10 weeks building the vehicle, working on it at home and at school. The bike was assembled in the garage of one student, Greg Shewchuck, and the plastic bag was cut and designed at another student's home.
Using margarine containers as models, students finally decided to build a 13-foot diameter octagonal frame.
"If it's too big it's inefficient, and if it's too small it's too hard to work," said Greg.
The 20-member class spent only $65 building the Hovercraft. The Dorsey's Search Business Association contributed $200, and Hechinger's and Clarks Do-It Center donated wood and plastic. A Westminster furnace repairman gave the class a furnace fan.
To move the 130-pound Hovercraft, a student simply pulls it by a rope attached to its frame.
Students said they didn't have enough time to build a self-propelled Hovercraft, which would have required a propeller fan on the back of the frame.
Besides operating Hovercrafts in Sunday's competition, the students also competed against the clock in contests that had them dragging their craft 50 feet, and pulling it around an obstacle course of three cones.
Physics teacher Stan Eisenstein said his students have learned a lot from building the Hovercraft.
"They did have to learn a lot of physics and they got the experience of getting from an idea to bringing it to fruition," Mr. Eisenstein said. "I wanted to give them that experience, not solely academic work."
Students said they also treasured the opportunity to put their academic skills to work.
"We actually got to do something instead of just doing it on paper," Greg said.
The most difficult part was "getting everyone together and agreeing on stuff," student Jae Lee said.