Standing at the start of the Wild Zipline Safari in Cumberland, Ohio, I felt a little woozy. I was 7 meters (23 feet) above the ground. Thick cables stretched between tall towers in the hills below me. I was about to hang from those cables and zoom from tower to tower.

My guide attached my harness to a pulley system on the first cable. I took a deep breath and stepped off the tower. WHOOSH! I sped down the cable and began my journey. 

I didn’t travel to Ohio just to zip. I also wanted to learn how zipline courses like this one are made. So I spoke to engineer Larry Gerstner. He designed the Wild Zipline Safari and several other courses in the area.

Top Speed

To design a zipline course, Gerstner first studies an area’s terrain. He uses high-tech tools to measure the elevation at different points. That helps him decide where—and how high—to build each tower. 

Ziplines rely on gravity to pull riders down the cables. That means Gerstner has to build each tower lower than the one before it. The bigger the height difference, the faster the riders will zip. 

Other factors affect speed too. Wind can slow riders down or speed them up. Even a rider’s position plays a role. I noticed that I went fastest when I curled my body into a ball. Making myself smaller reduced drag, the slowing force of air pushing against me.

Gerstner’s team does many test runs on a new course. They adjust each cable until riders reach a top speed of 64 kilometers (40 miles) per hour. That’s Gerstner’s “sweet spot”—a speed that’s both exciting and safe. 

Bird’s-Eye View

Speed isn’t the only fun part of a zipline. Gerstner also wants to give riders amazing views. He’s built courses that whisk people past cliffs, caves, and waterfalls. The Wild Zipline Safari is located in a conservation center for endangered animals. I saw giraffes and wild horses below me as I sailed by. 

Riding the zipline was tough work. I had to use my stomach muscles to balance in a sitting position. Near the end of each zip, I pressed down on the cable with my gloved hand. This created friction, or rubbing force, to help slow me down.

By the end of my ride, I was tired but thrilled! For Gerstner, watching people finish a course is the best part of the job. “I love seeing how excited they are about what they’ve accomplished,” he says.