Brenna Swift, The Union Democrat

A group of local students will haul homemade catapults to San Jose this weekend for an unusual contest at The Tech Museum of Innovation.

The 15 homeschooled students formed the Tuolumne Tech Club this year to prepare for the museum's popular Tech Challenge.

The challenge this spring was for students to design contraptions that will launch eggs onto three targets without breaking the eggs, a task that isn't as easy as it sounds. They've spent weeks building catapults out of wood, cardboard and bungee cords.

Tech Challenges come with storylines: The eggs represent fragile "scientific instruments" being deployed onto a model "asteroid" to measure its chemical composition.

The rules for the competition are strict. For example, students have to find a way to trigger a launch while standing at a safe distance. Eggs can be cushioned, but their containers can't have wings.

"It's just difficult," said Cristiana Hatler, 13, whose competition team built a trebuchet - a type of catapult - out of cardboard and wood. "It has to be inside all the guidelines and everything and not crush your egg."

Tech Challenge teams can also get awards for "team spirit," which resulted in the Tuolumne County students giving their teams colorful names like the "Tie-Dye Miners," "Krazy Kelts" and "Galaxy Surfers."

They've got team uniforms, too. The "Tech Troopers" are wearing camouflage, the "Krazy Kelts" are wearing kilts and the Tie-Dye Miners will wear their namesake clothing.

"There's a little nervousness about the ability of the devices to work according to plan," said Tuolumne resident Holly Britton, who has two children in the tech club. "But everyone's excited about it."

The Tuolumne Tech Club started when the Britton family watched the Tech Challenge in San Jose last year.

"We went there and we saw all the people having so much fun and launching things," said Ellie Britton, 14. "We all thought it was really fun-looking."

The students had to journal their expenses and write about team dynamics, which has been an educational experience in and of itself.

"I've learned a lot about how to deal with a team and how to keep on track when there's four teenage girls wanting to laugh and talk and make jokes," Ellie Britton said.

The Tuolumne Tech Club is supported in part by the Sonora-based technology company Front Porch. The Brittons' father, Zach Britton, is Front Porch's founder and CEO.

Parents have helped the club take off, Holly Britton said. They plan to take teams on field trips to gear up for next year's Tech Challenge and would like to turn the club into a nonprofit.

Meanwhile, the Tech Challenge - which also has competition sites in San Diego and New York - is roping in more students. A record 3,500 are participating this year.

The contest is sponsored mainly by technology companies and open to grades five through 12 in three age divisions.

"If you ever have a chance to go, it's phenomenal," Holly Britton said. "It's loud and big and colorful."