M.Simons The World's Vintage Sailplanes 1908-45
In 1923, along with the Konsul, the Darmstadt Akaflieg brought out the first practical, dual-controlled training two-seat sailplane. Resplendent in doped fabric and clear varnish, the Margarete was named after Margarete von
Loessl, widow of Eugen von Loessl who had been killed at the first Rhoen meeting in 1920. The wing planform was at first a simple rectangle with nearly square tips. The aerofoil was Goettingen 533. Two spars took the bending and twisting loads and plywood covered the leading edge. The ailerons, as on the Konsul, were of vast area, triangular in plan and hinged diagonally. The fuselage was plywood covered and of a neat, semi-streamlined form. The wing was in two sections, joined on the centre line and bolted to the fuselage frames at the rear spar position only. Large 'V' struts braced spars to the fuselage. The pilots sat in tandem, the rear seat being well back beneath the wing. At the root, a strong central member carried loads from the front spar back to the pylon aft of the rear cockpit, so the second pilot’s view was not obscured by a forest of struts. The gap where the wings joined at the centre was covered by a laced fabric fairing. The pilots had no windscreens. The tail unit was large and angular.
Early flights proved that the elevator and ailerons, cable driven, were inadequate in spite of their size. Modifications were made, the ailerons were redesigned to a form with narrower chord and less area. This would reduce the control forces needed. There were no further difficulties and the Margarete became very popular. The two seater attended every important gliding meeting for four years, carried many passengers, and introduced many young pilots to soaring flight. In August 1925 at the Wasserkuppe. Hesselbach soared with a passenger for just over three hours and later, on the Crimean expedition, nearly doubled this with a remarkable record flight of 5 hours 52 minutes. By 1928 the Margarete had outlived all the gliders, including the Konsul, that had flown at the 1923 meeting. Probably it had, like all two seaters ever since, been overworked and abused. Standards of inspection and maintenance were somewhat lower than they were later to become and four years’ flying had taken their toll.
The end came in a crash caused by a broken aileron cable, fortunately without serious consequences for the pilot, Bubi Nehring, at the Rhoen in 1928.
Margarete: Span, 15.30 m. Wing area, 25 sq m. Aspect ratio, 9.36 Empty weight, 180 kg. Flying weight. 320 kg. Wing loading, 12.8 kg/sq m. Aerofoil, Goettingen 533.
Flight, September 1922
The Darmstadt Machines. - Of the various "groups" that competed at Rhon the Hannover students did best of all, owing to the remarkable flights made by Martens and Hentzen on the "Vampyr." So much was this the case that nearly all the first prizes were won by representatives of the Hannover High School. Other institutions, however, also collected respectable prizes, notably the Darmstadt "group" (Akademischer Fliegergruppe, Hochschule, Darmstadt), whose students had entered three machines for the competition. By the courtesy of Flugsport we are able to publish, in addition to our own photographs, general arrangement drawings of the three Darmstadt machines, two of which are monoplanes and one a biplane.
Of the three Darmstadt machines the one which appears to have done best is No. 4 ("Edith" ) , which was piloted by Bottsch. This machine, which is shown both in photographs and scale drawings, is a parasol monoplane, in general arrangement not unlike the Hannover "Vampyr"; that is to say, it has a ply-wood covered fuselage with a monoplane wing placed above. The wing construction is, however, somewhat different from that of the Hannover machine, notably on account of the employment of two wing spars. The "Edith" is not a true cantilever machine, as two struts on each side slope outwards for a considerable distance from the lower longerons of the body. The monoplane wing is straight and non-tapered both in chord and thickness, and is built up of two halves joined on the centre line of the fuselage. As in the Hannover, the entire leading edge is covered with three-ply wood to give extra stiffness and to retain the shape. The fuselage is rectangular section with a triangular portion added behind the pilot's seat. The undercarriage is in the form of two skids (flexible) of ash. The weight of the machine empty is stated to be 200 lbs., so that assuming a weight of 160 lbs. for the pilot, the total loaded weight is 360 lbs. and the wing loading 360/172 = 2.1 lbs./sq. ft., which is fairly high for a glider. Nevertheless, Bottsch on this machine was awarded third prize in the competition for slowest rate of descent. The Darmstadt monoplane No. 6 ("Geheimrat") was piloted by Hackmack, and received second prize in the slow rate of descent competition. Generally speaking, the "Geheimrat" is not greatly different from "Edith," but its monoplane wing, is divided into three separate portions, a large centre section and two tapered end pieces. The wing is so mounted that the angle of incidence can be adjusted during flight. The weight of the machine is the same as that of the "Edith" (200 lbs.), as is also the wing loading. The wing is carried on two vertical extensions of the sides of the fuselage, and no external bracing struts are employed.
The third Darmstadt machine is a small biplane with a short enclosed nacelle and open tail booms. To a certain extent the machine is reminiscent of the early Caudron biplanes, except that the skids on which it lands are not continuations of the lower tail booms, but are a separate structure. The biplane wings show the usual wire bracing, but lateral control is by wing warping. One of our photographs shows the construction of the nacelle. As in the monoplane, three-ply wood is extensively used.
In our introductory remarks it was pointed out that the cantilever monoplane is necessarily somewhat heavier than a biplane structure. The wing area of the Darmstadt biplane is 150 sq. ft., and the weight empty is 110 lbs., so that with pilot on board the wing loading of the biplane is approximately 1-8 lbs./sq. ft., in spite of the fact that the area is some 22 sq. ft. smaller than that of the monoplanes. On the other hand, the monoplanes probably have a considerably higher maximum lift coefficient.
THE DARMSTADT MONOPLANE GLIDER "EDITH." In the illustration the machine is just getting away. Note the tow rope dropping from its quick-release in the nose of the fuselage.
The Darmstadt monoplane, piloted by Bottsch, flying over the Dresden biplane.
The Darmstadt monoplane, of which scale drawings were published in our issue of September 21, 1921. Herr Bottsch just managed to land the machine before striking the trees, but damaged the fuselage in doing so.
Herr Bottsch in the cockpit of the Darmstadt machine. Note the quick-release in the nose of the fuselage. This machine has made flights of long duration, one being of 1 1/2 hours.
Two-seater Gliders: Front portion of the "Margarete" (No. 35), showing two cockpits and peculiar mounting of the monoplane wing.
The Margarete preparing to launch. The name, Margarete, was inscribed on the nose in joined script.
THE MARGARETE: A glider of the intermediate type being flown by the flying section of the Technical High School at Darmstadt. They gained the first prize for the two-seater class in the Rhon Gliding Competition.
A two-seater glider at Rossitten: The Academic Flying Group, Darmstadt's "Margarete," in flight over the Kurischen-Haff. Note the kind of country over which the machines fly.
From the Rhon Meeting: No. 46 ("Moritz") and No. 35 ("Margarete") in the air together. On this occasion "Margarete" is not carrying a passenger.
TWO DARMSTADT FUSELAGES: Top, the body of the Type 4 monoplane; bottom, the nacelle of the biplane.
THE THREE DARMSTADT MACHINES: General arrangement drawings.