Following the ideas of the inventor both the German army and navy used the Zeppelins for strategical reconnoissance in the early days of the conflict. The Zeppelins flew the western and eastern boundaries of the empire seeking information concerning the movements of the Allied armies. This proved dangerous, however, for the airships then could not rise to high altitudes; and consequently were exposed to enemy fire from the batteries below and airplanes above.

The L-3 operated with the fleet in the North Sea and her activities served to show the value of supplying as quickly as possible Zeppelins able to fly high and with greater speed than ever. It was also found advisable to cease flying over land by day. The Zeppelins became the night cruisers of the air, and were assigned the task of destroying railway junctions, bridges and ammunition dumps along the enemy line of advance.

The Navy soon acquired the Zeppelins L-4, L-5, L-6 and L-7, which joined the L-3 in the North Sea operations where they became indispensable as the eyes of the fleet and a continual menace to the enemy attempting to establish himself on the German Coast. All these airships were duplicates of the L-3 except in minor details. Their hulls long and cylindrical, of uniform cross sections, that is excepting the ends each part was the same size as the others. This was the first attempt at standard construction and it permitted quantity production more economical and quicker for they were not compelled to design and fabricate each section as it was needed. The plant at Friedrichshafen had been expanded and was working to capacity. Every effort was made to save time. The result was remarkable for they were able to produce one Zeppelin every six weeks. Late in 1914 the Zeppelin Z-11 was delivered to the army and the L-8 to the navy.

The Growth of the Zeppelins

Larger sheds (Plates 8 and 9) were completed at Friedrichshafen enabling Zeppelin to build bigger ships which could give the performances he felt was essential.

The first of these, the LZ-38, left the shed in April, 1915, and joined the army. It had 1,130,000 cubic feet (32,000 cubic meters) of hydrogen capacity and was fuller, that is, its ratio of length to diameter was 9 to 1 where in the former ships it was 11 to 1. The wider girth afforded more freedom in design and the stern was drawn out much finer, resulting in more speed; on later ships reaching 58.1 miles per hour (26 meters per second). The LZ-38 could carry a useful load of 30,865 pounds (14,000 kilograms) besides her own weight, more than 37% of her total lift. The Zeppelins of this type (Plate 10—LZ-77) proved from the day they were first flown equal to all the demands made upon them.

North Sea Patrol Flights

They cruised over the North Sea scouting and guarding the coastline, remaining in the air for thirty hours at a time. They flew out from the western outlet of the Kiel Canal, northward along the shores of Denmark to the Norwegian coast and thus were able virtually to command the sea hundreds of miles around with powerful glasses.

One day when the true details of the Skagerrak Naval Battle are given to the world, it will realize the vital part which the Zeppelins played. They consistently hampered the enemy’s mine laying operations and rendered timely and valuable support to the counteractions of the fleet. In discovering mines they were particularly effective; and this work alone, about which the world was uninformed, justified fully the time and labor put into their construction.

Ten Zeppelins of the L-38 type were delivered to the navy in 1915, numbered from L-10 to L-19 inclusively. Approximately as many were turned over to the army during the year, each one being slightly improved. Zeppelin and his staff of experts were always able to profit by the practical experience which the ships were undergoing almost daily.

Zeppelins Become Lighter and Stronger

The hulls were strengthened and made more rigid, yet lighter, machine guns were mounted at proper points of vantage and bomb dropping apparatus so perfected that heavy loads of explosives could be carried in absolute safety, yet instantly released and with remarkable accuracy. An observation car was added to each new ship.

The Zeppelin Observation Car

This car was one of the most unique inventions developed during the war. It could be lowered with an observer aboard, fully one kilometer (3,280 feet) below the Zeppelin. Here the observer could get his bearings while his ship lay far above hidden in the clouds. The ship could fly or drift above the clouds to a point directly over the spot to be bombed, then by lowering the car with the observer through and just below the clouds, he was able to direct both the operations of the ship and the bombing. A telephone connection ran up through the supporting cable. He was able to signal for bomb releases and navigate so efficiently that any objective could be attacked without danger of the enemy seeing the Zeppelin lurking behind the clouds.

Another Zeppelin, the L-20 was delivered to the navy early in 1916. It had hydrogen capacity of 1,271,160 cubic feet (36,000 cubic meters) though the diameter was the same as the others. The L-20 carried a useful load of 37,478 pounds (17,000 kilograms), and an increase of 1,312 feet (400 meters) over their ceiling and made the same speed with the same horsepower.

During the year Zeppelin delivered seven more ships of this type, but possessing greater efficiency. The navy received five of them and the army two.

Anti-Aircraft Defenses Compel Zeppelins to Fly Higher

The Allies meanwhile had developed anti-aircraft defenses and their airplanes possessed greater climbing ability. To meet these new conditions the airships were continuously compelled to fly higher. They also required speed greater than the average of 54 miles per hour (25 meters per second) because while navigating over the North Sea they frequently encountered winds of from 33.5 to 40 miles per hour (15 to 18 meters per second).

To meet these conditions the L-30 was built (Plate 9). It had a gas capacity of 1,942,000 cubic feet (55,000 cubic meters) and was nearly twice as large as the original 1,129,920 cubic feet (32,000 cubic meters) four motored ships. The L-30 was ready in May, 1916. It was almost perfectly streamlined. The long cylindrical hull, so convenient from a production standpoint, had been abandoned. The L-30’s stern tapered gracefully to a fine point. It was driven by six 240 horsepower Maybach motors, arranged practically as before. One was located in the forward gondola with a direct drive propeller, another three motors in the rear gondola, one with a direct drive and two others each in a separate gondola located opposite each other on the sides of the hull amidships, so as not to interfere with the efficiency of the propeller in the rear gondola. The L-30 carried 63,933 pounds (29,000 kilograms), about 45% of its total lift. Other Zeppelins of her class had a useful lift of 50% due to better design and superior materials. This represented a marked advance, as the preceding types lifted only 37% of their weight. The ceiling had been increased, too, by more than 3,280 feet (1,000 meters). They could now ascend from 11,800 to 14,750 feet (3,600 to 4,500 meters), depending on the load and weather conditions. They made a speed of 63 miles per hour (28 meters per second).

Faster Zeppelins for Scouting

These Zeppelins proved exceedingly valuable for scouting. They were flown in all kinds of wind and weather. So great was their capacity for fuel that there was no task too great for them to undertake. But then, airplanes were constantly being improved, and they could rise quickly to high altitudes. The planes carried machine guns firing phosphorous incendiary bullets fatal to the hydrogen filled hull of the Zeppelins if overtaken. Airplanes, naturally, could out-distance airships, and there was no escaping them. The Zeppelins were compelled to fly still higher than the L-30 type. There shortly appeared other Zeppelins carrying loads of more than 39 tons or 60% of the total lift of the ship; and they could fly at an altitude of 19,684 feet (6,000 meters) with 13,228 or 15,432 pounds (6,000 or 7,000 kilograms), without depending on the thrust from the motors.

In the fall of 1917 “altitude” motors were developed, larger and having supercompression. They did not develop full power at sea level but instead functioned normally at 10,000 feet altitude above sea level. They, moreover, gave ample power higher than that. They speeded up the Zeppelins to 70.5 miles per hour (31.5 meters per second).

The Zeppelin company built thirty-six ships of this type (Plate 10-L43), from 1916 to 1918; and they were used by the army and navy. The British R-34, which crossed the Atlantic in 1919, was an exact duplicate of the Zeppelin L-30 type.

Zeppelin Vision of World Transport

Count Zeppelin was working on his post-war plans for commercial aerial transport when he died in March, 1917. His latest ships had demonstrated their worth as cargo carriers, not only in war but in peace. Before hostilities commenced he had seen thousands of passengers carried in his Zeppelins. An account of these operations will be found in Chapter III.

His Will Carried Out After His Death

They had justified the inventor’s faith and inspiration. He had never abandoned his ideas of world transportation and was completing a survey of requirements and conditions to be met when, during a flight, he contracted inflammation of the lungs. Though mortally ill and old in years—he was seventy-eight—Count Zeppelin held conferences in his sick chamber, passing on to his assistants the big idea of airship transportation. They have since continued the work where Count Zeppelin left it. Following the funeral at Stuttgart airships dropped garlands and wreaths of flowers on his grave, in honor of the man who had done so much and had perfected an organization capable of performing the tasks remaining.

The Record Flight of L-59

There is ample proof of what a modern Zeppelin can accomplish when commercially operated and not forced to operate at the highest possible altitude and maintain maximum speed. In November, 1917, the Zeppelin L-59 (Plate 11) was sent to German East Africa with medicines and ammunition for the beleaguered colonial troops. The Zeppelin was especially prepared for the flight, all superfluous equipment, such as bomb dropping apparatus and armament being removed, all available space reserved for the cargo. The L-59 was longer by 98.5 feet (30 meters) than the others. This made room for two additional gas bags. Inside her 744½ foot hull (227 meters) were 2,381,000 cubic feet (68,000 cubic meters) of hydrogen. She could carry 50 tons easily. With only five motors she averaged 62.6 miles per hour (28 meters per second).

Flown from Germany to Jambol in Southern Bulgaria, the L-59 was there loaded with 9 tons of machine gun ammunition and 4 tons of medical supplies and with 21 tons of gasoline for the motors.

4225 Miles in Less than Four Days

The great Zeppelin sailed out of Jambol (Plate 12) at 9 o’clock in the morning, crossing northwestern Asia Minor, then the Aegian Sea, south of Smyrna and on between the Islands of Crete and Rhodes and across the Mediterranean, reaching the African Coast by daybreak the next day.

The great Sahara Desert was then crossed, the L-59 passing over the oasis of Farafrah and then Dakhla. Military headquarters at Berlin, meanwhile, were trying to reach the Zeppelin by wireless. The German Intelligence Office had intercepted a British wireless message to the effect that the Colonial troops had surrendered to the British. The L-59 had passed through a severe storm the night before and had taken in her radio antenna; and it was not until she was over Djebel Ain, west of Khartum that she listened in and picked up the message. In a day and a half the L-59 had traversed 1865 miles (3,000 kilometers). Without stopping the Zeppelin was turned about; and after retracing its path across the Sahara, thence over the Mediterranean to Adalia on the coast of Asia Minor, and flying high over Asia Minor and the Black Sea, arrived back in Jambol in less than four days from the time it set out from that port. There remained sufficient fuel aboard for two or three days additional flying. The ship, under the same conditions, could have flown from Hamburg to Khartum and return. As it was she traveled 4,225 miles (6,800 kilometers) on a non-stop flight which, though it occurred in 1917, today remains the world’s record for all kinds of aircraft, airship or airplane.

Larger Zeppelins More Powerful

During the summer of 1918 the Zeppelins were again given higher climbing ability to meet the ever-increasing efficiency of planes and anti-aircraft guns. Another gas bag was added to the new ships (Plates 13 and 14), which brought them up to 2,189,220 cubic feet (62,000 cubic meters) capacity. In order not to diminish the speed two motors were added in respective gondolas, making seven engines in all, aggregating 1820 horsepower. They could carry 94,798 pounds (43,000 kilograms) or about 60% of their total lift. It was planned to add improvements enabling them to reach an altitude of 26,240 feet (8,000 meters) but the armistice halted all military activities and there was no occasion at that time for commercial craft to fly so high.

The Most Remarkable Scientific Development in the History of Aeronautics

Looking back over the development of the Zeppelins (Plate 15), one fails to find such remarkable and quick advance in any other medium of transportation. The history of engineering does not record in any other science progress comparable to that of the relatively new science of lighter-than-air as represented by the Zeppelins during the four years of war.

Seventy Percent Speed Increase

Their speed had increased from 46.6 to 87.5 miles per hour (75 to 130 kilometers per hour) approximately 70%. Their horsepower averaged 2,000. To carry useful loads of 44 tons their hydrogen capacity had been raised from 706,200 to 2,189,220 cubic feet (20,000 to 62,000 cubic meters). Other commercial ships were built embodying the improvements developed during the war. A description of them will be found in Chapter III.

Refinement in Design

This progress was made possible only by continuous experiments. Ideas and suggestions were adopted regardless of expense or chance of failure. In this way the Zeppelins had the advantage of every conceivable refinement in design. Their hulls, motor gondolas, in fact, all braces and wires were streamlined so as to offer the least air resistance.

The rubberized cloth gas cells, or bags, used in 1914 had been discarded for others of light yet strong cotton cloth (and often silk), lined with goldbeater’s skin to make them hydrogen proof.

Many of the experiments were as costly as they were painstaking but the Zeppelin engineers had learned early in their work that airships can not be built satisfactorily without long and arduous experiments to support each innovation. By continually striving to increase efficiency they secured simplified control systems and ships that handled more easily, hulls that were far more rigid yet lighter than their predecessors. Even the framework was lightened as by degrees it was made stronger. Many structural parts were standardized, facilitating production and repairs.

One has an idea of the innumerable parts necessary in the skeleton of a Zeppelin when he learns that more than 250,000 small crossties are required in making the triangular shaped girders in the frame work of a 1,977,300 cubic foot (56,000 cubic meters) ship which crosstie is a masterpiece of construction, because of its ingenious shape and finish.

Eighty-Eight Zeppelins During the War

Few persons know that during the war alone Luftschiffbau-Zeppelin designed and built 88 airships at their four great construction plants, as follows:

That in itself was a remarkable achievement which could have been accomplished only by possessing the scientific knowledge borne of experience. But it is not all.

One Hundred and Fifteen Zeppelins Built and Operated

From the day Count Zeppelin built his first ship until the last in 1919, a total of 115 Zeppelins were built and operated. The first three were experimental. Nine Zeppelins were successfully operated commercially in the transportation of passengers. Forty were delivered to the German army and 63 to the navy.

Scientific Comparison

There exists in the field of engineering an impartial, positive and unswerving means of determining the relative merits of things; and that is by a technical analysis of their success. By it one may recognize the values of the principles and construction methods involved. It is commonly said that nothing succeeds like success; and this is virtually true of the Zeppelins. Their record for efficiency remains unsurpassed, as a matter of fact, unequalled. It has never been denied that they were superior to contemporary craft or that they failed to maintain an increasing advantage over them.

This comparison is justified by the following figures which we will first attempt to explain.

It will be noted that there are three kinds of efficiency, (1) Speed (the aerodynamical figure), (2) Lift (the constructional figure) and (3) All-around efficiency (the combined quality figure).

The first relates to the efficiency of airship propulsion as effected by degrees of refinement in form, lessening of resistance, conservation of power, etc. It is simply the relation between the speed and engine power. Inasmuch as higher speed with the same power or the same speed with less power means economy of operation; therefore, the higher figure indicates superior quality.

Secondly, referring to the lift, this constructional figure indicates the relative useful or pay loads carried with the smallest amount of material used in the ship itself, because the ship, which must also be carried is “dead weight.” As we must consider all ships equal as far as structural safety is concerned, the technical performance is determined by judging the relative performance in carrying useful loads (for ships of similar size), or equal loads with smaller ships, which means economy of operation. The higher figure indicates superior quality. It should be noted that this constructional figure is applicable only to comparison of airships of similar size, speed and service requirements. For general comparison, however, ships of approximately the same size may be considered.

Thirdly, all-around efficiency (the combined quality figure) is somewhat arbitrarily chosen by considering both the speed and carrying qualities together. It is not based on scientific deduction, but rather is a practical means of estimating general worth, as speed and carrying capacity are the main requirements of an airship.

Efficiency Characteristics of Some of the Latest and Best Airships of All Nations

Scientific deductions and formulae to be found in “Zeitschrift für Flugtechnik und Motorluftschiffahrt,” June 15th and June 30th, 1920, issues. Article by P. Jaray.

CHAPTER II

The Zeppelin Organization at the Time of Its Greatest Activity 1918-1919

The Zeppelin Endowment for the Propagation of Air Navigation (Zeppelinstiftung zur Foerderung der Luftfahrt) which Count Zeppelin founded with the subscription fund of 6,000,000 marks presented to him by the German people in 1908, is administered by a Board of Directors, of which Baron Max Freiherr von Gemmingen, Zeppelin’s nephew, who worked with him from the start, is Chairman. The other Directors are Baron von Bassus and Dr. Hugo Eckener.

The Zeppelin Endowment owns Luftschiffbau-Zeppelin (Zeppelin Airship Building Co.), the construction company organized in 1908 and controls the “DELAG” organized, as stated before, in 1910 for the operation of commercial Zeppelins. Interested in the “DELAG” are a number of financiers, though with all the others, it was under the personal supervision of Count Zeppelin, and after him the Directorate of the Zeppelin Endowment.

At the time of the Armistice the construction and operating companies employed 1,600 persons on their executive and engineering staffs and 12,000 workmen.

Many subsidiary companies were organized and operated, specializing in the various branches of Zeppelin work, experimenting and producing.

Many Subsidiary Companies

These subsidiary companies are also controlled by the Directorate. They were not permitted to disintegrate during the difficult period following the war, but instead, have kept their personnel and facilities intact and are ready to continue the work which was interrupted by the terms of the treaty. They produce respectively motors, gas bags, propellers, gears, sheds and, in fact, everything pertaining to aerial navigation including airplanes, flying boats and parts.

The Construction Plants

The great construction plants are organized on the same principles as ship yards. Over them all is the General Director, Mr. Alfred Colsman, and Chief Engineer, Dr. Ing. Ludwig Dürr, the latter having been with Count Zeppelin since the first airship was started and to whom much of the credit must be given for the success attained.

There are various departments including the planning and supervising divisions, two designing divisions (one for scientific and general design, the other for workship and drawings), the manufacturing and erecting divisions, calculating and accounting, testing and controlling, and general maintenance divisions. The research department is a separate organization.

The Airship Factories

In the airship factories the framework is made and erected. The envelope is prepared, passenger and engine gondolas completed and assembled along with other apparatus and instruments. The power plant is built, excepting the motors and parts of the gear work. Research work along the lines of airship development is conducted there.

The original plant built at Friedrichshafen in 1910 included a double shed, workshops, offices and laboratory buildings. The shed would not accommodate ships of greater diameter than 52½ feet (16 meters), so in 1914 new workshops and another shed was built, to be followed the next year by a still larger shed.

During 1915 and 1916 better workshops (Plate 16), offices and a larger laboratory, together with the largest wind tunnel on earth were completed, along with a low pressure chamber for testing motors, a new development as unique as it was important to the automotive science.

The Hydrogen Plant

The original hydrogen plant was enlarged to a capacity output of 353,100 cubic feet (10,000 cubic meters) daily, with storage facilities for 2,118,600 cubic feet (60,000 cubic meters). Since the war, the storage facilities have been reduced to 706,200 cubic feet (20,000 cubic meters) by order of the Allied Commission.

Powerful Radio Station

The Zeppelin wireless plant, started in 1910, has continued to develop with the science of radio and is now able to communicate with the United States.

The duralumin factory is capable of meeting all Zeppelin requirements.

The Great Zeppelin Hangars

The original shed, built in 1908-09 and first used in 1910, is now the ring building factory, where the great transverse frames for the Zeppelins are made. It is 603½ feet (184 meters) long, 150.8 feet (46 meters) wide and stands 65.6 feet (20 meters) high—huge dimensions in the early days but utterly dwarfed by the great sheds which have since appeared alongside. There are double doors at each end, one set operated on the turning, the other on the sliding principle. They are opened and closed by electricity in a few minutes.

In this shed twenty-eight Zeppelins were assembled, the last being LZ-39 after which it was devoted to the transverse ring frames.