Experimenter

NOV 2014

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

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30 Vol.3 No.11 / November 2014 THE WINGS OF QUICKSILVER WHEN I SAW DAVE CRONK for the first time, I was 29 years old and a bushy-haired, bell-bottom-jeans-wearing new pilot. We were both at the early mecca of soaring—the wonderful Torrance Beach bluffs in Los Angeles—where hang glider pilots flocked every day, and particularly on weekends, to try their hand at soaring the onshore Pacific winds. On any given day, scores to a few hundred observers would park and walk to the north end of the bluf s that rose higher southward toward the Palos Verdes Peninsula. They came to see this crazy new fl ying magic up close and personal. It was 1974. Other than a few zanies like myself, the world knew little about the Rogallo wing design or foot-launched flying in general. Most people thought we were a bunch of hippiefied misfits with one common trait: a death wish. I had come to mecca—with a couple months of glides and not a single soaring flight under my belt—to worship the masters, learn from them, and most of all, join that still-elite group of pilots who could magically work the lift band to fly for more than a handful of ground-skimming moments. At one point as I was setting up my Seagull III glider in the sand, a flash of white caught my eye. I looked up to see a hang glider that was dramatically different from the pointy-nosed Rogallos that dominated the scene. This craft had a fairly high aspect ratio, a rectangular (decidedly not Rogallo-shaped) wing, and a conventional tail complete with a horizontal stabilizer and a movable rudder. It was a gorgeous bird: the crisp, all-white Dacron sail- cloth wings and tail were set of by a sparkling airframe made entirely of bronze-anodized aluminum tubing. The handsome pilot was equally striking. He was lean and athletic, with a serious demeanor, and his long brown hair fl owed back in the wind. In that moment, I wished I could be just like him, to be so at ease plying the lifting air in his angelic craft. I noted, too, his distinctive head-forward slouch, seated in the "harness"—little more than a playground swing seat—and was reminded of a sprinter lunging for the finish line tape. "Wow," I said to another pilot. "What the heck is that?" He followed my gaze and said, "That's Dave Cronk and his Quicksilver C. He's the head designer at Eipper-Formance." I knew about Dick Eipper, the pioneering hang glider company he formed, and its popular line of quality Flexi Flyer Rogallos. Eipper leaped ahead of the garage-builder crowd with a well-marketed operation and never looked back. And the Quicksilver C was apparently its latest innovation. I marveled at the performance of the Quick. While the rest of us struggled in the 12-mph ocean breeze to achieve that elu- sive dream of sustained fl ight along the rising ridge at Torrance, Dave made everybody look like a bunch of neophytes. Where we beginners were lucky to gain maybe 100 feet above the top of the ridge in one pass before losing the lift, Dave navigated the lift band at will, like he was one of the local seagulls. Taunting us, he'd ease straight out from the ride to fl oat beyond the waves, exploring the upwind edge of the lift band, then swinging in a graceful arc back toward the ridge…and still end up higher than everybody when he got there. It wasn't the last time I'd share the air with Dave Cronk…or the Quicksilver. A SHAPE OF DESTINY That iconic wing/tail design, for so long a mainstay of hang gliders, ultralights, and now special light-sport aircraft (S- LSA), did not begin life in the fertile brain of Dave Cronk. The monoplane twinkle in his eye originated, probably in late 1971, with fellow Eipper-Formance designer Bob Lovejoy's original High-Tailer. The High-Tailer had excellent performance, but it also had one shortcoming: It was too stable and didn't turn worth a darn. Back to the drawing board. The Quicksilver A that emerged from the High-Tailer's redesign used the same 30-foot-span, 4-foot-chord wing. But in place of the twin vertical tails was a horizontal, A-frame tube arrangement angling back from the trailing edge of the wing. A cable-braced, fi xed horizontal stabilizer and rudder fi nished of this new "fuselage." The rudder was moved by lines fi xed to either side of the simple plastic swing seat. As the trailing edge of the rudder's C-shaped frame was unsup- ported, the rudder distorted a lot. It was still ef ective at yaw- ing the tail suf ciently for the dihedral of the wings to come into play and ef ect a turn. A stif er "D"-frame rudder solved the distortion problem. Cronk and Lovejoy kept tweaking the design. Load testing uncovered weakness in the trailing edge and that was fi xed. Once the Quicksilver B model debuted, ready-to-fl y for all of $965 (twice of what a Rogallo cost), the Quick legend was on its way to glory. Before long, the Quicksilver C debuted with an increased span of 32 feet, a deeper chord (to 5 feet), and a larger tail. The airfoil camber was reduced from 12 to 8 percent camber. Jack Schroeder, another free-fl ight pioneer, joined Dave Cronk to fl y Photography by James Lawrence Dave Cronk fl ies the original Quicksilver No. 1.

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