Engineering a Sand Castle

On a recent Monday afternoon, four Tufts students were kneeling in the hot sand on Revere Beach, mixing sand and water in a bucket, then packing the mixture into a big, hollow LEGO brick. They were trying to make the building blocks for small structures to surround a large, two-foot-tall sand castle.

The first mixture was so damp and tightly packed that it wouldn’t come out of the mold. The second batch came out, but immediately fell apart—too dry. The third ratio produced a perfect mold and a chorus of “Wow!”

“As much as you try to plan, you still need to test and go back and retry and change directions”—it’s the essence of the engineering process, said Nicole Batrouny, a mechanical engineering grad student. Wei-ren Murray, A20, a computer science and cognitive science major, said it’s similar to the debugging process used in computer science. “You have to look at and test every part of your code, because any part could result in an issue,” she said.

Batrouny and Murray were at the beach along with child development grad student Emily Fuller and English major Samantha Leong, A20, attempting to build a two-foot-tall sand castle that could house their “clients,” a handful of LEGO people and survive the tide.

The real objective wasn’t just to build a sand castle, of course, but to learn more about how engineering works in fun, creative ways. Murray, Fuller, and Leong are summer interns at the Center for Engineering Education and Outreach (CEEO) working on K-6 engineering education initiatives for local schools, and learning like young kids learn—by doing—was their goal.

Waves crashed onto the shore, seagulls swooped and cried overhead, and the sun shone down through a thin layer of clouds as the students, armed with a colorful assortment of plastic buckets, LEGO bricks, and egg cartons—mostly gathered from the CEEO—poured water on the sand to create a flat surface. They then dug a moat using large, flat shells, working quickly and efficiently. “I haven’t done this in so long,” laughed Batrouny.

After perfecting their sand-water mixture, Leong and Fuller started slinging handfuls of it onto the flat foundation to create a mound. “We can only build a tower as wide as the base is,” Batrouny said, referring to the civil engineering concept of the angle of repose, or how steeply you can pile up a loose, granular material before it starts sliding off.

But as they packed the outside of the castle with wet sand and spritzed it using spray bottles, the group observed that the moisture made it sturdier, and decided to go higher—much as a writer’s plan can change during the writing process, said Leong, who hopes to go into children’s publishing after graduating. “You do a rough draft and keep revising until you have a final product,” she said.

At one point, Fuller pulled out a ruler to measure the castle. “I would say fourteen-point-five inches,” she reported, and Batrouny plugged the number into the iPad where they were storing goals and data. As the castle continued rise, Batrouny crafted two arched sand bridges using her hand as a support, a technique Murray dubbed “technical glopping.”

LEGO people were posed on and around the castle. “Our clients are real fixer-uppers,” Murray joked. Leong crafted a spire at the top of the castle and artfully dribbled wet sand over its slopes. The castle was measured again: more than two feet. “Success!” said Fuller. “Huzzah!” said Murray. Batrouny did a celebratory pirouette in the sand.

As a finishing touch, Murray collected shells and pressed them into the sides of the castle. “To make it prettier and better for the LEGO people,” Batrouny said. “We want to keep our clients in mind.”

The group didn’t end up building smaller castles around the main structure as they had planned, and because the tide was receding, they didn’t get to check how their work held up against the water. “We had ideas at the beginning that didn’t pan out,” Batrouny said. “But that’s something that always happens no matter what you’re doing in engineering.”

Fuller, who’s researching how children develop role models, considered the project a success. “It’s about getting in touch with your inner kid, keeping at things until you get them right, not taking it too seriously, and having fun with it,” she said.

Monica Jimenez can be reached at monica.jimenez@tufts.edu.