Experiments ahoy!

Here's a challenge: Build a kayak out of tape and a 1.5-meter by 2.1-meter piece of cardboard. Too easy? Maybe not, if you're the one who has to climb aboard and race the boat in water.

Students at the San Francisco Community School dove into this project with no fear--once they discovered their teacher wasn't trying to drown them. By doing science experiments, they learned to modify Eskimo kayak designs so their cardboard versions would carry them to the finish line.

"We had to make do with what we had, and that was just cardboard and tape," says student Cory Brown. To conserve materials, Brown and his classmates started by making scale models--smaller versions with the same proportions as the big boats they would eventually build. Using cardboard sheets 12 times smaller than the assigned dimensions, they built a kayak with a narrow bottom and pointed ends--just like a real Eskimo kayak.

But as soon as the kayak hit the classroom's scaled-down ocean (a tub of water), the tiny boat tipped over and sank. That's when the experimenting began.

First, the students thought about all the variables (e.g., bottom width, boat depth, overall shape, and so on) they could change to make the boat more stable. Making a list of all these independent variables (variables an experimenter might change) and the dependent variables (variables the changes might affect) is a good way to start any experiment. The list helps you get a handle on all the things you could study.

CHARTING A CHANGE

But you can't just change every variable at once. If the San Francisco students had done that, they never would have known which variable, or variables made the boat more (or less) stable.

Instead, they decided to test the independent variables one at a time, to see how each affected boat stability (the dependent variable). They kept all other variables constant, or unchanged, so these other factors wouldn't interfere with the results.

The first variable one group of students changed was boat-bottom width. Before doing the tests, they made a prediction about what the result would be. They hypothesized, or guessed, that making the bottom wider would make the boat more stable.

To test their hypothesis, the kayak builders compared their new wide-bottom boat to their first boat design, the control. (Without something to compare the new design to, how would they know if their change had any effect?) Like real scientists, the students ran repeated trials, floating the new models again and again, recording what happened each time.

Did the hypothesis hold water? Yes. The results showed that wide-bottom boats were indeed more stable.

The students later ran similar experiments with other variables to see, for example, which boat could hold the heaviest load.

TAKE THE PLUNGE 

When all the tests were done, it was time for the students to scale up their models. In groups of three, they constructed life-size racing kayaks, based on the models they had tested in the classroom. "We had to measure very carefully to make sure each part was the right size," says student Baudy Gonzalez.

With the kayaks complete, each group waterproofed the hulls by covering them with tape. Then they decorated the kayaks with traditional Eskimo and nautical designs.

From the shore of Richardson Bay, the students launched their vessels and paddled toward the finish line--90 meters away. "This was the most exciting part of the project," says Gonzalez. Not sure whether her team's kayak would float, she let another teammate do the racing.

In the end, the hard work and experiments paid off. All of the boats floated ... at least at first. Some of the kayaks with slightly more narrow bottoms tipped and sank, leaving paddlers waist deep in the shallow bay. But the Eskimo Sea Lion, the kayak with the widest bottom, and the heaviest coat of tape, won the race. It floated merrily, merrily, merrily, merrily all day long.