GROSS III.
ZEPPELIN AIRSHIP STRUCTURE.
Obviously there is a material advantage in having many gas cells and two propelling plants; for if one fails it may not prevent navigation. The tandem arrangement of bags separated by the wheel-like cross bridges also allows the balloon to rear any amount without material displacement of the gas, or dangerous increase of pressure; for it must be remembered that a single hydrogen sac extending the full length of an up-ended balloon of such length, would have an outward pressure of about thirty pounds per square foot greater at the top than at the bottom. The poise of the vessel is maintained by shifting weights, and also by use of fins, or rudders, when driving through the air; but those arrangements vary in the different machines. So much for the general features of these wonderful ships, of which four were built during the decade from 1898 to 1908, and several more since that period.
The construction and trial of Count Zeppelin’s first air ship proved a formidable task, requiring all his resources of money and mechanical skill. As it rivaled in size and fluid displacement a large ocean liner, it could not well be launched and landed, except on the water. It was therefore housed in a wooden shed 472 feet long, floating on 95 pontoons, and so anchored as to swing freely with the wind and assume its direction. This shed, as well as the ship, was very costly, and in an unfortunate hour was torn from its moorings by a tempest, which did other damage entailing great expense and time for repairs. The inventor’s resources were becoming strained; for, as reported, the shed cost $50,000, while the first balloon cost more than twice that sum.
Finally, the first launching was officially set for June 30, 1900. The lake was thronged with people massed along the shores, and dotting its surface with every kind of craft, from the fisherman’s primitive boat to the handsomest private yacht, or launch. All day the expectant multitude waited, only to learn at dusk, that the inflation was not completed. Next day they tarried again till evening, and merely saw the raft on which the balloon rested, towed out of the floating house. On the third day, July 2d, those who waited were rewarded with an interesting spectacle. The long stiff air ship was drawn forth from its shed, like a ram rod from a gun. Count Zeppelin, with two men, occupied the front boat, while two others took the rear one. After careful adjustment the vessel was liberated, at eight o’clock, rose slowly and advanced over the water, accompanied by the droning of its propellers and the shouts of the delighted spectators, who realized that they might be witnessing the commencement of a new epoch in aërial navigation. But the voyage was not an unqualified success. The controlling mechanism became deranged, the framework was bent, and the propellers could not be worked properly. A gentle wind was blowing and the vessel drifted with it, having an independent speed of only thirteen feet per second, at best. At eight-twenty she reached Immenstadt and landed on the water, having voyaged three and one half miles, and having attained a height of thirteen hundred feet on a part of the journey.
At that date the Zeppelin I was by far the largest and most elaborate air ship ever constructed. Her hull measured 416 feet long, 38 feet across, cubed nearly 400,000 feet, weighed 9 tons, and had a displacement of 10 tons. The trellised frame was made of aluminum, and its body comprised seventeen compartments, of which fifteen were 26 feet long, and the other two 13 feet long. The outer cover was of linen treated with pegamoid and tightly stretched. The hydrogen sacs were of thin fabric. The propulsion was effected by two benzine motors, one in either boat, which together developed 32 horse power, each driving, by means of bevel gears and shafting, a pair of four-blade propellers 3.77 feet in diameter, at 1,100 revolutions per minute. Steering sidewise was effected by means of vertical rudders, while the trim was controlled by horizontal rudders at either side of the vessel, as also by means of a sliding weight which could be drawn fore and aft by means of a winch. Naturally some of these details were superseded ere long by better devices suggested by subsequent experience.
On October 17, 1900, Zeppelin I made her second voyage, and with much better result. Starting from the same balloon house at Manzell, at four-forty-five, she promptly rose a thousand feet, and maneuvered in a seven-mile wind, steering in great curves at the will of the pilot. At times the speed was nearly twenty miles an hour, as determined by continuous observations of the balloon’s position, taken from three points of a triangle, together with the velocity of the wind on its course, duly recorded by an anemometer. Finally a landing on the water was made at six o’clock, without mishap.
This last demonstration left the Count triumphant in other respects, but without sufficient funds to bring his invention into practical use. He must, therefore, look for additional money for the proper continuation of his great work. The financial task thus ensuing occupied much of his time during the next five years, but he finally secured capital enough to continue his experiments and to build a second airship. This was completed and ready for trial in the latter part of 1905.
Zeppelin II resembled its predecessor in appearance, but embodied many improvements suggested by the former trials. Its hull was 414 feet long, 38 feet in diameter, held 367,000 cubic feet of hydrogen in its sixteen gas bags, and weighed with all appliances and cargo, about nine tons. It was, therefore, about ten per cent smaller than its predecessor; but at the same time it was far better powered than the earlier one, and more effectively controlled. Each boat carried an 85-horse-power Daimler benzine motor, actuating two enlarged propellers. Ample steering surfaces, operated by the helmsman in the front boat, served to turn the great ship about either of three axes and, at the same time, to displace her bodily up and down in the air, either by direct lift or by canting her hull so that her screw thrust and the pressure on her sides would produce the desired translation.