Glasflugel H.301 Libelle
In 1954 Eugen Hänle was then Assistant Professor Ulrich Hütter in a company engaged in the manufacture of large wind turbines for electricity production. The design of the 17 meter blades used fiber reinforced plastic glass.
With this experience, Eugen Hänle established Glasflügel in 1957, to produce helicopter rotor blades for Bölkow.
Meanwhile, Hütter had developed the H-30TS glider, derived from the H-30, with a modified fuselage to accommodate a small BMW turbojet and a new wing of 15 m with plastic flaps, but with glued aluminum sheet metal spar. Hänle then used the molds to produce wings in the Schempp-Hirth workshop. Two sets of wings with glass fiber spar were made. One of the wings was the first H-301 Libelle (or Dragonfly), other than the first Swiss Diamond, with its original 15 m wingspan.
Designed by Wolfgang Hutter and Eugen Hanle, the Libelle first flew on 6 March 1964 and became the first fiberglass sailplane to receive an U.S. ATC. Although of Standard Class span, its camber-changing flaps and manually retractable monowheel put it into the Open Class; it could, however, be flown with flaps up and wheel locked down to conform with the then Standard Class rules. The two-piece cantilever mid wings are glass-reinforced plastic/balsa sandwich structure with a single spar web and no ribs; the glassfibre spars are joined at the fuselage by a tongue/fork type of junction which was later to be adapted in a number of other sailplane designs. The mass-balanced ailerons are linked differentially with the flaps, and there are Hütter air brakes, each 8 ft 2.5 in long, forward of the flaps. The wing leading edge has a compartment for water ballast, of which 110 lb can be carried.
The fuselage is an all-glassfibre monocoque with balsa and synthetic foam and an integral fin; and the rest of the tail unit is of the same type of construction as the wings. The pilot sits in a semi-reclining position under a rearward-sliding one-piece canopy to reduce fuselage cross-section and hence drag, and a slightly higher canopy could be fitted if the customer so desired; there is provision for radio and oxygen, and the seat backrest and rudder pedals are adjustable in flight. The monowheel is mounted on a glassfibre shock absorber and has a brake; it is supplemented by a sprung tailskid or tailwheel.
In 1969 Soaring magazine readers voted the Libelle the World’s most beautiful sailplane. The H 301 Libelle has camber-changing flaps and was able to compete both in the Open Class and, with locked flaps, in the Standard Class.
A total of 111 Libelles had been built when production finally ceased in 1969.
Wing span: 15 m / 49.2 ft
Wing area: 9.5 sq.m / 102.25 sq.ft
Length: 20 ft 4 in
Height: 2 ft 7.8 in (wheel up)
Empty Weight: 180 kg / 397 lb
Payload: 120 kg / 264 lb
Max speed: 155 mph (smooth air)
Max aero-tow speed: 84 mph
Gross Weight: 300 kg / 661 lb
Wing Load: 31.25 kg/sq.m / 6.4 lb/sq.ft
Aspect ratio: 23.6
L/DMax: 39 at 95 kph / 51 kt / 59 mph
MinSink: 0.55 m/s / 1.8 fps / 1.07 kt at 46.5mph