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Eipper-Formance Quicksilver (Hang-glider)

Cronk Quicksilver

 

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Designed in 1972 as a hang-glider by Bob Lovejoy.


The popular Quicksilver monoplane hang glider was developed it into a very good power glider. With its twin-boom tail support structure, an engine mounted from the wing center section it offers gen-tle and forgiving flight characteristics and is generally foot-launched, though landing gear can be added.

 

Eipper-Quic-02
Quicksilver B
 
The origin of the Quicksilver can be found in Bob Lovejoy's High-Tailer design. The High-Tailer and early Quicksilvers all had a 4 foot chord and 30 ft span.
 
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.

The Eipper guys thought to load test the Quicksilver and the failure occured at very low G, 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 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 Quicksilver B, designed by Bob Lovejoy, was available as ready-to-fly, kit form, or as plans. The airframe is aircraft aluminium tubing, wings and tail surfaces are dacron covered. Pitch is weight-shift controlled, while the swingseats connected to the rudder controls turns.
 
A Quicksilver B kit in 1974 cost $545 and plans sold for $5. Ready to fly the Quicksilver B cost $965. A custom colour wing cost an additional $30.

 

There were homebuilt versions including one in 1974 with polyethylene covering instead of sail cloth.
 
 Eipper-Quic-03

 

Mark Clarkson, flying a Quicksilver in the spring of 1974, flew seventeen miles (measured as a straight line between take-off and landing). The farthest anyone had flown in a hang glider.
 
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 its 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. The C model seemed to be the most prolific of the hang glider models.
 
Cronk-Quic-B
Cronk Quicksilver B

 

All HT and Qs models to this point had a tube for a trailing edge. 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). Dave Cronk said it ruined the stall characteristics (very sharp and abrupt), but penetration went WAY up. This may have been called a "D" model. 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 was a rocket in Cronk's hands, though it appears none were sold to customers.

 

First year motorised 1976.

Hang-glider
L/D: 7-1.
Cruise: 18-25 mph.
Gross wt: 395 lbs.
Empty wt: 155 lbs.
Max pilot wt: 220 lbs.
Takeoff dist: 40-50 ft.
ROC: 250 fpm.

 

Quicksilver B
Wingspan: 30 ft
Wing area: 116 sq.ft
Weight: 56 lb
Cruise speed: 22 mph
Max speed: 32 mph
Stall speed: 17 mph
Max glide ratio: 7-1
Min sink: 250 fpm

 

 

Cronk Quicksilver B
 
Wing area: 10.80 m²
 
Wing span: 9.15 m
 
Aspect ratio: 7.75
 
Hang glider weight: 25 kg
 
Minimum speed: 35 km/h
 
Maximum speed: 50 km/h
 
Max glide ratio (L/H): 7
 
Minimum sink rate: 1.3 m/s

 

 

 

 


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