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.

[PLATE 18: The Maybach Motor Works, 1916.

Practically all of the Airship motors were made in this plant.

Zahnradfabrik Friedrichshafen, G.M.B.H., 1915. (The Cog-wheel and Gear Works).

Part of Friedrichshafen and Lake Constance in the background.]

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.

[PLATE 19: Maybach Airship Motor of 145 Horsepower, 1911.

Maybach Airship Motor of 180 Horsepower, 1913.]

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 cla.s.s 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).

[PLATE 20: Maybach Airship Motor Type HSLu of 240 Horsepower, 1915.

Maybach Airship and Aeroplane Motor Type Mb4a of 260 Horsepower at an Alt.i.tude of 10,000 Feet, 1918.]

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 alt.i.tudes. 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 alt.i.tude 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 "alt.i.tude" motors were developed, larger and having supercompression. They did not develop full power at sea level but instead functioned normally at 10,000 feet alt.i.tude 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 pa.s.sengers carried in his Zeppelins. An account of these operations will be found in Chapter III.

[PLATE 21: Zeppelin Giant Seaplane Built at Potsdam Plant, 1917.

Zeppelin-Dornier Twin (Tandem) Motored All Metal Commercial Flying Boat, 1919.]

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, pa.s.sing on to his a.s.sistants 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 alt.i.tude 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 s.p.a.ce 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 744 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.

[PLATE 22: Zeppelin-Dornier All Metal Flying Boat Type DoRs III, 1918.

Zeppelin-Dornier All Metal Flying Boat Type DoRs IV. 1918.]

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 pa.s.sing 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 pa.s.sed 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

[PLATE 23: Zeppelin-Werke Staaken Giant Biplane in Comparison With Pursuit Plane, 1916.

The Giant Biplane had a wing spread of 137.76 feet and carried a useful load of 4 tons. Its power plant totaled 1250 horsepower and made a speed of 90 miles per hour.

Zeppelin-Dornier All Metal Pursuit Plane Type DO D1, 1918.

Note the absence of all struts and wire bracing.]