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Schleicher Rhönadler / Seeadler

Jacobs Rhönadler

DFS Rhonadler

 
Schl-Radler-1
 
About 1931 the glider manufacturer Alexander Schleicher went to Hans Jacobs, then at the RRG (Rhön-Rossitten Gesellschaft) on the Wasserkuppe, for glider design that, like the RRG Fafnir designed by Alexander Lippisch, was capable making long cross country by travelling quickly between thermals but could be put into series production making it cheaper to build. Jacobs responded with the Rhönadler (in English, Rhön eagle), ready for the 1932 Rhön competition. The following year both Jacobs and Lippisch had to transfer to the state owned DFS (Deutsche Forschungsanstalt Für Segelflug) at Darmstadt, where Jacobs continued to refine the Rhönbussard, hence the DFS Rhönadler name.
 
The Rhönadler was a wood framed aircraft with plywood and fabric covering. In plan its high wing wings were straight tapered with a torsion resting D-box form by ply skin ahead of the single spar. Aft of the spar the wings were fabric covered. The Rhönadler wing root used a version of the thick Göttingen 652 section, modified by a reduction of its high camber; further outboard this turned into the progressively lower camber Göttingen 535 and Clark Y airfoils. Dihedral was constant, to avoid the constructional complication of the Fafnir's gull wing. The ailerons were very long, occupying more than half the span. Though neither the prototype nor later production aircraft came with spoilers or airbrakes such devices, opening above the wing, were often retro-fitted.
 
The Rhönadler's fuselage was quite slender and entirely ply covered, including the fin, the balancing part of the rudder and a small tail bumper. On the original version, even the cockpit canopy was a ply structure, with small, unglazed apertures for vision. This was progressively modified with increasing glazing into the 1935 variant's multi-framed conventional canopy. To avoid the wing root aerodynamic interference that the Fafnir's gull wing was intended to avoid, the Rhönadler's wing was mounted just above the fuselage on a low, narrow neck or pedestal which placed the leading edge level with the top of the canopy. The high aspect ratio, all-moving horizontal tail was of similar construction to the wing, with most of the taper on the trailing edge where there was a deep cut-out at the root. The tailplane was low set on the prototype but raised just above the dorsal fuselage line on production aircraft. The broad chord, balanced rudder was also fabric covered. Landings were made on a sprung skid under the forward fuselage.
 
The Rhonadler (or Rhon Eagle) first flew in 1932; at this time the techniques of long distance soaring flight were beginning to be explored in earnest by sailplane pilots, and distance covered rather than time spent airborne was what pilots were aiming to achieve. At the 1932 Rhön the Rhönadler, flown by Peter Riedel, did not win but impressed enough to go into series production as the Rhönadler 32, with the prototype's wing span slightly shortened, its vertical tail leading edge smoothed by a shorter rudder balance and its tailplane raised. This sold well, though production numbers are uncertain. The 1935 version's alterations included a fully enclosed transparent canopy. Schleicher built sixty-five of them, making it the top selling German high performance glider; several were exported. A measure of the popularity of the Rhönadler is the number at the 1935 Rhön competition, twenty-three out of sixty contestants.
 
RhonAdler-2
 
Production was undertaken by Schleicher at Poppenhausen. Sixty-five Rhönadler 35 were built. In the 1980s a new Rhönadler was built from original plans and flown. It is now in the Wasserkuppe museum.
 
Variants:
Rhönadler
Prototype. Competed in the 1932 Rhön event. 18 m (59 ft 1 in) span. Ply fairing over cockpit with small oval openings for vision.
 
Rhönadler 32
First production version, with raised tailplane and simplified fin and rudder. Span reduced by 542 mm (21.3 in). Transparencies at the front of the cockpit.
 
Rhönadler 35
Second production version with full cockpit transparencies.
 
Seeadler
Flying boat version with hull, markedly gulled wings and underwing stabilizing floats.
 
Specifications:
 
DFS Rhonadler
Length : 23.622 ft / 7.2 m
Wingspan : 57.087 ft / 17.4 m
Crew : 1
 
Schleicher Rhönadler
Span: 57 ft 1 in
Length: 23 ft 7.5 in
Wing area: 193.8 sq ft
Aspect ratio: 16.8
Empty weight: 375 lb
Max weight: 551 lb
Max speed: 80.5 mph
Min sinking speed: 2.5 ft/sec
Best glide ratio: 20:1
 
Rhönadler 35
Length: 7.20 m (23 ft 7 in)
Wingspan: 17.40 m (57 ft 1 in)
Wing area: 18.0 sqm (194 sq ft)
Aspect ratio: 16.8
Airfoil: Root: modified Göttingen 652; mid-span: Göttingen 535; tip: Clark Y
Empty weight: 170 kg (375 lb)
Gross weight: 250 kg (551 lb)
Maximum speed: 130 km/h (81 mph; 70 kn)
Stall speed: 50 km/h (31 mph; 27 kn)
Maximum glide ratio: 20:1
Rate of sink: 0.75 m/s (148 ft/min) minimum
Wing loading: 13.6 kg/sqm (2.8 lb/sq ft)
Crew: One

 

dfsrhonadler
DFS Rhonadler



 


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