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By Al Bowers:
" The origin of the Quicksilver can be found in Bob Lovejoy's High-Tailer (sp?) design. The High-Tailer and early Quicksilvers all had a 4 foot chord and 30 ft span. IIRC, the High-Tailer had swept twin vertical fins that started at the control bar, passed the trailing edge of the wing (mostly the same as the original Quicksilver) and ended somewhat above the wing. A horizontal tail capped the two verticals off. Again, IIRC, the design had some directional control problems (it would almost always fly straight ahead, very stable), and the control bar/vertical/horizontal arrangement was somewhat flexible. It was a four sides parallelogram structure, so had little inherent stiffness. The original Quicksilver (later called the "A" model) was built from the High-Tailer. The twin verticals and high mounted horizontal were replaced with an "A" frame off the trailing edge of the wing, back to a fixed horizontal and a "C" frame rudder (no fixed fin). As the trailing edge of the "C" frame was unsupported, the rudder distorted a lot, but it was very effective at directional control, and the glider responded through dihedral effect (Cl-beta). The "C" frame rudder got replaced with a different "D" frame rudder which solved the distortion problem. I can't recall if it was Dave Cronk or Bob Lovejoy (or one of the other Eipper guys) that first thought to load test the Quicksilver. in any case, the failure occured at very low G (again, fuzzy memory, IIRC it was about 3.5 Gs), between the trailing edge flying wire and the center section. Also, the single upper wire to the tail didn't provide much lateral support to the rudder loads. These led to the to the first improved model of the Quicksilver, called the "B." A wire was added from the control bar to the trailing edge of the wing (increasing the G limit to about 5.5), the "A" frame of the tail group gained a straight section between the horizontal and the rudder (making a square "U" section) and a second upper wire was added from the kingpost to the tail (one wire to each end of the squared-off "U"). The result was the best of the early model Quicksilvers, as a flying machine and structurally. The next Quicksilver improvement was increasing the span (from 30 ft to 32 ft), increasing the chord (from 4 ft to 5 ft), and enlarging the tail (the rudder lost it's characteristic "swept" leading edge). The wing also gained square tips (cf the "tapered" tip of the HT/QsA/QsB) to make the Quicksilver C model. This model also had a much reduced camber of the airfoil (the High-Tailer through Quicksilver B model had a "670-15" airfoil, which was made by bending a thin aluminum tube for one-half of it's length over a 670-15 car tire; it was about 12% camber; the C and later models had about an 8% camber, again, IIRC). This was the same model that Jack Schroeder and Dave Cronk flew in the (much delayed) 1974 Nationals (I believe that Bill Liscomb was still flying an older B model at that meet). The C model seemed to be the most prolific of the hang glider models. There after, there were some experimental models meant to improve performance. And here the letter designations get very fuzzy. All HT and Qs models to this point had a tube for a trailing edge. I don't know if it was Cronk, or Lovejoy, or one of the other Eipper guys, but an experiment was made of moving the trailing edge spar forward, and making a thin trailing edge of fabric only. The leading edge pocket was also made VERY large (maybe about 50% of the chord). When I talked to Dave Cronk about this, he said it ruined the stall characteristics (very sharp and abrupt), but penetration went WAY up. this may have been called a "D" model. But I do know that later still the leading edge pocket was made even larger to enclose the leading AND trailing edge spars (about 80%) making a double surface airfoil. This model (the "E"?) was a rocket in Cronk's hands, though I don't think any were sold to customers. This would have been about the time of the first Fledge IIBs appearing in California with a similar pocket enclosing the spars (I don't know who did it first, or who copied who, or even if both came up with it independently of each other; I would guess the last option being the most probable). There were some competitors out there as well. Conquest was one (very high level of fit and finsh on these). Another (much less successful) was the Condor. The Qs was certainly the "performance" machine of the day until surpassed by Fledges. And the Rogallos started improving in this same time frame, Mike Riggs' Seagull V, Rich Finley's Windlord, Tom Peghiny's Peregrine, and Roy Haggard's (unbelievably radical) Dragonfly. Once you compute the transport and set-up hassles against the performance gain, the flexwings were more than competitive to most buyers. It's funny how things have come full circle. Now with Exxtasy, Ixbo, ATOS, and Millenium rigid wings easy to set-up and almost as easy to transport as flexwings, we're nearly back to parity again (complexity and weight still favor the modern flexwing). And I still get out my plans for the Quicksilver A/B once in a while and look at them. I have many fond memories watching Pat Conniry and Dave Cronk flying their Quicksilvers at Torrance Beach. And helping my friend, Sandy Klevans, set-up, launch and fly his Quicksilver... Al Bowers " |
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