“…The ability of sheet metal to carry an increasing load after it had begun to buckle – which in conventional structures was regarded as failure – was crucial to the development of metal airplanes. It had first been discovered in 1925 by Dr.Herbert Wagner, who was then working for the Rohrbach Metall-Flugzeugbau in Berlin, Germany, but his findings were not published until 1928 in English by NACA. Northrop’s work was done independantly. Wagner went further than Northrop in his analysis of the way in which a thin sheet of metal behaves when supported at the edges, as it is in airplane structures, and he evolved the theory of the diagonal-tension field beam to explain it. This theory, and elaborations of it, formed the basis for the development of a/c structures from the mid 1930’s onward. But it was not applied to the early Northrop airplanes or the Douglas DC-1-2-3. Northrop’s construction gave a good enough ratio of strength to weight for these airplanes, and the use of Wagner’s theory would have added to the complication and cost of design…”
The above quotation is from: Ronald E.Miller; David Sawers, “The Technical Development of Modern Aviation” (Routledge & Kegan Paul: London; 1968) p.65
In August 1933 Paul Kuhn wrote an explanation of Wagner’s theory as NACA Technical Note No. 469 “A Summary of Design Formulas for Beams Having Thin Webs in Diagonal Tension”, Langley Memorial Aernautical Laboratory. Washington,. A copy of this paper may be downloaded from the Herbert Wagner page on this website.
SCHWARZ, David
Born: Zalaegerszeg, Hungary, 20 December 1850
Died: Vienna, Austria, 13 January 1897
Timber merchant; airship designer
SCHWARZ, Melanie: his wife and business partner
SCHWARZ, Vera, their daughter; opera singer
A tin airship was brought to flight by David and Melanie Schwarz from Agram, Dalmatia (now Zagreb, Croatia). At the end of the nineteenth century, it was they who built the first metal airship in the world. The story is well documented by now (see links below) but remains remarkable because they were the predecessors of Graf von Zeppelin, who is generally assumed to have been the first to build the historic metal steerable, lighter-than-air vehicles that now carry his name.
It is also remarkable because here a woman played a decisive role in the construction of a flying machine. (In the first half century of aviation history there have been a good number of courageous and successful female pilots, I know, however, of no other example of a woman who was involved in the business of building a flying machine, nor have I ever heard of major contributions in this field by ladies such as Mme Blériot, Mrs. Boeing or Frau Heinkel…)
The husband, David, was a man of some importance, a timber merchant who every year spent long months in the forest, overseeing logging operations. His desire was for a magical, mighty machine that would be able to lift the cumbersome trunks of trees straight up and out of the hilly terrain. His thoughts materialized into the design of a rather large metal cylinder, filled with hydrogen gas. The pressure inside the vessel would equal the outside air, so as to avoid extreme forces on the shell. In order to be able to levitate, the total construction, plus its load, would have to be lighter than the air it displaced, according to the Law of Archimedes.
Being an avid reader of technical books, he had learned of the miraculous metal aluminium (or aluminum in English speaking countries), known since 1825 as silver-from-clay. As Wikipedia states: “Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth’s crust.” Yet it proved extremely hard to extract from its host, the ore bauxite. Indeed, the first small quantities produced were so costly that they were used only for art objects and expensive cutlery at the court of Napoleon III.
Aluminium Eros at Piccadilly Circus London, ca. 1895
Production on an indutrial scale had to wait until in 1886, when Charles Martin Hall in Ohio, USA, and Paul Héroult in France invented the electrolytic process of refining aluminium at practically the same time, using an electro-oven. This development was only possible after the perfection by George Westinghouse (and predecessors) of the electrical transformer, a device that could deliver to the oven extremely large currents at low voltage. The oven required a vast amount of electric power, which had become available on an industrial scale after Man had learned how to build hydro-electric power stations (for instance at Niagara Falls, 1895 and Neuhausen Switzerland, 1888). The production of relatively cheap aluminum became from then on feasible and Schwarz’s dream came into the realm of reality.
It goes without saying that in order to become truly dirigible, his tin cylinder would also need a motor with propeller and rudder (although for lifting tree trunks out of the woods a cable balloon might have served the purpose). The practical, portable combustion engine was put on the market around 1885 by Gottlieb Daimler and Carl Benz.
Summing up, we may say that the light-weight metal steerable airship could not have been built before 1890 and that Schwarz’s invention represented the cutting edge of technology.
Schwarz first approached the Austria-Hungary War Ministry, but received little interest in his ideas. He found more resonance in Russia and a first attempt by him to build a metal airship was made in St.Petersburg. When these attempts failed Schwarz returned to Zagreb.
In 1894 he got involved with the German entrepreneur Carl Berg from Ludenscheid, Westfalen. Carl’s firm specialized in the production of aluminum flat sheet and rolled shapes with various profiles. The factory obtained raw metal from the first European aluminium smelter in Neuhausen, Switzerland (1888), later known as Alusuisse. Berg saw great potential in Schwarz’s project and decided to help him transform ideas into hard reality. In fact, it was Berg’s engineers who made the definitive calculations and ultimate design for the airship. On paper it looked sort of like a giant spray can lying on its side: a cylinder with a flat bottom and a conical point. An open gondola hanging from the cylinder would hold the pilot, the Daimler engine (16 hp) and the steering controls. Via belts the engine drove no less than four propellers, one of them a horizontal one to aid levitation. According to one account the ship measured 38 meters (125 ft) from tip to tail; its diameter was 12 meters (40 ft). The aluminium skin was 0.2 mm thick (equal to four sheets of kitchen aluminium foil) and riveted air tight on a skeleton of thirteen aluminium hoops and longerons of angle profile. Important: at the highest point of the cylinder was a hydrogen release valve that could be opened from the gondola.
Berg and Schwarz came to the agreement that Berg would assume all further costs. He would produce the parts that were to be assembled under the supervision of Schwarz at Tempelhof Airport in Berlin. It took till the summer of 1896 to get the metal airship ready. Then it was discovered, during the last preparations for the first flight, that the so-called hydrogen gas supplied by a German chemical factory was not of sufficient purity; its specific weight was not low enough in comparison with the air it was displacing and so the loaded airship would not float upwards. Further tests had to be postponed.
Central Cemetery of Vienna – Israelite part
To the great dismay of his family and business associates, David Schwarz was hit by a fatal stroke while in Vienna on the 13th of January, 1897. The Jewish community of the city of Vienna gave him a funeral with all due honor and a monument at the Zentralfriedhof of the city.
Carl Berg feared he was now stuck with a bizarre and rather fantastic-looking aluminium cylinder whose inventor and promoter had taken his leave forever. However, high-quality hydrogen gas was delivered in Berlin at that same day and Melanie Schwarz came to the rescue. Contemporary sources state that she was a “delicate yet unbelievably energetic lady”. Apart from caring for her family she had always assisted David in his endeavors. Everybody was surprised when she took charge of the project. The preparations for the first flight were resumed resolutely. She engaged a Mr. Jagels, a military man who had, as he said, some experience in ballooning and who was prepared to wager his life for a modest compensation .
Berlin: Tempelhof Field
Filled with almost pure hydrogen gas, the tin cylinder finally elevated itself from German soil in the presence of a vast crowd on the 3rd of November, 1897. A hard and cold wind blew from the east. Jagels had practiced ballooning under simple circumstances; now it was demanded of him to observe a multitude of variables such as wind, altitude, obstacles, engine revs and desired course, while at the same time handling the engine, the drive belts and the rudders. The ship did lift off, but thereafter things went wrong. The drive belts jumped from their wheels, the propulsion failed and the little ship was carried off, out of control, by relentless and swirling winds to a height of more than four hundred meters. Caught in a basket and at the mercy of the elements, this height is frightening to even the most obliging person and it is understandable that Jagels did the only thing that he could possibly think of: he yanked hard at the cord that opened the safety valve. Unfortunately, just like Blanchard ninety years earlier, he let too much of the good gas escape. The ship, suddenly having lost its buoyant force, dove down and, zigzagging like a punctured child’s balloon, struck the earth at an oblique angle. Fortunately, the skipper was able to jump just before the metal cylinder flattened the gondola against the ground and so saved his dear life.
Melanie showed a remarkably modern talent for public relations. She dispatched the following telex to Carl Berg:
“HYDROGEN FILLING AND LIFT OFF FULLY SUCCESSFUL” STOP
“SHIP ATTAINED 1000 FT MADE 2 TURNS” STOP
“DRIVE BELT PROBLEM CAUSED PREMATURE LANDING” STOP
“SHIP DAMAGED” STOP
“JAGELS UNHURT“ STOP
“MELANIE SCHWARZ“ STOP
Unfortunately, this diplomatic account of affairs could not withhold Berg from withdrawing from the project. He had the remnants of the ship melted. (One of the curious properties of the new metal was that it could be completely recycled.)
Melanie appeared one more time on the stage of history when a certain Count von Zeppelin approached Carl Berg to embark with him on a new project for a metal airship. “This ship will be completely different. It will have an exo-skeleton of aluminum girders that will be covered by watertight fabric. The gas will be held inside in a row of conventional balloon bags.” Berg was highly interested but felt himself tied by contract to the Schwarz estate. To nullify the obligations, the following proposal was made to the heirs: during a three-year period the Schwarzes would be paid the equivalent of 15,000 Reichsmark, with a royalty of 10,000 Reichsmark for every airship delivered, with a maximum of thirty airships. To their surprise, the generous offer was turned down by the guardian of the Schwarz children, Herr Czillac from Fiume. This male meddling infuriated Melanie and she personally made an appearance at Berg’s headquarters. She was willing to tear up the contract for an immediate payment of 15,000 Reichsmark. “Cash in hand,” she must have reasoned, “that silly old fool Zeppelin won’t ever amount to anything!”
In hindsight, this is a shame, of course, because the thirty airships mentioned in the proposal would already be built by Graf von Zeppelin before 1915, and the previously mentioned three hundred thousand Reichsmark would have been just the sort of money that a mother-alone-with-children could have put to great use.
Epilogue
Vienna Staatsopera
All together we may safely state that Melanie did well in the end. Her daughter Vera Schwarz(188?-1964) became with dedicated maternal care a famous soprano, appearing in all the major opera houses of Europe and the United States, often together with Richard Tauber. From 1938 to 1948 she lived in exile in the U.S. Upon her return to Vienna she became a sought-after teacher, giving well attended master classes.
In 2011 a street in Vienna’s 23rd district was named Vera-Schwarz-Gasse in her honour.
ritstaalman 