Last summer, Bell towed the catapult to a local lake to try it out with some friends. He sat in the chair as a buddy threw open a ball valve, retracting a piston with compressed air. The arm sprang up within a second, hurling him high above the lake. "This smooth but sudden sensation launches you upward, and then, all of a sudden, you say, 'Hey, I'm not in the chair anymore,' " he says. "I came out of the water hootin' and hollerin' like a teenager." Bell says the catapult's official debut at Bridge Day later that year was just as big a hit among BASE jumpers. "It's something I'll remember for the rest of my life," he says.