M.Simons The World's Vintage Sailplanes 1908-45

THE WEIHE

  By 1938, Hans Jacobs had completed more than ten years as a sailplane designer. His Reiher was the best production sailplane in the world but was too expensive. He had learned a great deal during its development, and these lessons ДальшеMore>>> were now incorporated in his new venture, the Weihe. (The Weihe is a large bird of prey, a member of the kite family, quite common in some parts of Germany.) Baltic pine and birch ply were the most readily available materials, and mild steel was used for all fittings. The Weihe was to be cheap, easy to fly and safe for club pilots, yet capable of advanced performance, strong and stable enough for cloud flying in rough air, and practical to operate from the typical, rough and sometimes sloping ground of club hill soaring sites as well as from flat aerodromes.
  The span was larger than most contemporary club single seaters but nevertheless smaller than the Reiher. The aspect ratio, the single most important factor for reducing drag at low speeds, was as high as Jacobs could make it without excessive cost. For the sake of strength and stiffness, the wing was strongly tapered, allowing a deep mainspar at the root, but Jacobs avoided the very sharp taper of the Rhoenadler wing, which was, aerodynamically, going too far. The aerofoil was the Goettingen 549, changing to the less cambered NACA M-12 at the tip, with washout. The Weihe had a tank capable of carrying 20 kg of water ballast.
  The ailerons were long and fairly broad, making them somewhat heavy on the stick. The rate of roll was adequate but not very rapid. A dihedral angle of 2 degrees, increased slightly on the production aircraft, combined with large fin and rudder areas, gave good stability in turns. At high speeds the ailerons became progressively heavier, a common feature on sailplanes, the cause being the torsional flexibility of the wing.
  Airbrakes were fitted, fairly well back on the wing, and of the type developed by the DFS. In normal flight the brake paddles remained flush with the wing surface in shallow recesses. On opening, the upper paddle came out of its recess and moved forward to an angle of about 45 degrees to the airflow, whilst the lower paddle moved down and back, the loads on the upper and lower sides balancing one another so the pilot could open the brakes at any airspeed without strain. Fully open the Weihe brakes were much less effective than the vertical, parallel-ruler type developed by Huetter for Schempp Hirth.
  All the wing bending and torsional loads were taken by the box-section mainspar combined with the plywood-covered 'D' nose, with the plywood laid diagonally to increase the torsional strength. There was no rear spar, the ailerons being hinged to specially strengthened wing ribs and, at their inner end, supported by a plywood-covered box that also housed the airbrake mechanism. At the root, the customary heavy diagonal spar and triangular torsion box, were omitted. Instead, a short stub spar was built inside the ‘D‘ nose, and this carried the front fitting where the wing joined the fuselage. Behind the mainspar, there was no connection between wing and fuselage. A gap existed all the way back to the trailing edge from the mainspar connection point. Pilots who knew a little of aerodynamics always made sure this was taped up before flight. Each wing was attached to the fuselage at two points, the front, torsion or drag fitting, and at the lower flange of the mainspar. The upper spar flanges were joined directly to one another, on the centre line. The main pins were mounted in tubular slides and could never be lost or misplaced. They were connected by toggles and pushrods and locked by the ‘over centre' movement of the toggle handles. Ailerons had to be separately connected but the airbrake linkage was automatic. Three men could rig a Weihe in a few minutes.
  The fuselage of the Weihe had a low neck or pylon for the wing mounting. Jacobs believed that shoulder or mid-wing mounting positions were not only more difficult to engineer but also in circling flight could cause flow breakdown over the wing roots. There would almost always be some sideslip or crossflow in this region, and he thought it better to leave the upper surface of the wing clear of obstructions. There was no attempt to fair the wing root junction, except for a small extension of the wing mount pylon upward near the trailing edge to carry the lines down to the rear fuselage.
  The cockpit was roomy and comfortable, with space for oxygen gear and other equipment behind the seat. The simple transparent canopy had two large windows, big enough for the pilot to get an eye outside to look straight ahead in conditions of rain or icing. The landing skid was sprung by a long row of tennis balls, a two wheeled drop-off dolly being used for ground handling and taking off.
  Two prototypes flew in the 1938 Rhoen competitions. The Weihe was adopted by the NSFK as their standard high performance sailplane and quantity production began. During the war years, about 280 Weihes were built by Jacobs' own Schweyer works and more at other factories in and outside Germany. Most of these remained in service until captured by the Allied forces in 1945. Many were then destroyed, but a few were ‘exported’, and some were used by the British service gliding clubs during the occupation.
  The Weihe remained at this time the best available sailplane in the world. In Spain, France and Sweden, production began again and in Yugoslavia about 35 were also built, these having improved brakes of the Schempp Hirth type and ‘blown’ cockpit canopies. In 1952, the Focke Wulf Company in Germany produced the Weihe 50, which had some detailed improvements, a Perspex bubble canopy and in some cases, ailerons of reduced span. These proved as effective as the older, larger ones. Some had landing wheels.
  It is impossible to mention all the outstanding flights made in Weihes. The most famous of all Weihes was that used by Per Axel Persson to set the world gain-of-height record at 8050 metres in 1947 at Orebro in Sweden. Persson went on to win the World Championships in 1948 in this aircraft, and it was flown again to victory by Billy Nilsson at the 1950 World Championships. It still survived in 1980.
  Also outstanding were the great duration flights made in Germany during the war. Vergens, in 1942, soared for 45 hours 28 minutes over the sand dunes in East Prussia and the following year Ernst Jachtmann stayed aloft for 55 hours 51 minutes. In 1980 a number of Weihes remained in service.

  Technical data:
  Weihe: Span, 18.00 m. Wing area, 18.20 sqm. Aspect ratio. 17.8. Empty weight, 215 kg. Maximum flying weight, 335 kg. Wing loading, maximum 18.41 kg/sq m. Aerofoils, root, Goettingen 549 and wingtip, M-12. Best glide ratio, 1:29. Maximum permitted speed 170 km/h.

M.Hardy. Gliders & Sailplanes of the world

DFSWeihe

  The Weihe single-seater high performance competition sailplane was designed for the DPS by Ing Hans Jacobs, who was responsible for so many of the leading prewar German types, such as the Meise, Kranich, Rhonadler and Rhonsperber. The Weihe was developed from an earlier gull wing design known as the Reiher and first flew in 1938, being placed fourth in the Rhon competition of that year. It soon aroused the interest of prospective customers and more than 550 were eventually built in Spain, France, Sweden and Yugoslavia as well as Germany, and including a few built after the war as the Weihe 50 by the Focke-Wulf company when it was reconstituted at Bremen Airport as Focke-Wulf GmbH. The Weihe remained in the front rank of competition sailplanes for a very long time; it took first place in the 1948 World Gliding Championships flown by Per-Axel Persson of Sweden, and at these championships no less than 13 out of 29 competitors were flying Weihes. The type also took the first two places in the 1950 World Championships and third place in the 1954 World contest, being able to hold its own with the many more advanced postwar designs then in use. Persson, who had won the 1948 World contest, had set a world height record of 26,411ft in his Weihe the year before, and in 1959 a Weihe set another height record of 31,709ft. The 18m span wings have a thin Gottingen 549 aerofoil section, and small spoilers are fitted just inboard of the ailerons. For rigging the high cantilever wings are fitted into the fuselage with their tips on the ground, the tips then being raised and the wings locked into position with a bolt. The Weihe is of conventional wooden construction; the fuselage is rather long with a narrow cross section that makes for a somewhat cramped cockpit. The canopy was originally of the multi-framed type with a sliding window, but the later Weihe 50 had a more streamlined one-piece canopy. Take-offs are made on a jettisonable dolly wheel landing gear and there is a landing skid under the forward fuselage. Nine Weihe 50s were built postwar by Focke-Wulf GmbH, the prototype of this series first flying on 14 March 1952.


Data: Weihe 50
Span: 59 ft 0 1/2 in
Length: 26 ft 8 1/2 in
Wing area: 197.4 sqft
Aspect ratio: 17.7
Empty weight: 507 lb
Max weight: 539 lb
Max speed: 140 mph
Min sinking speed: 1.9 ft/sec at 37.5 mph
Best glide ratio: 29:1 at 43.5 mph