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Aviation History
1925
1925 - 0202.PDF
APRIL 2, 1925 MODERN ZEPPELIN AIRSHIPS NOT only because of the interest at present being taken in airship questions in this country, but also on account of the manner in which the lecturer dealt with his subject, the paper read by Herr Dr. Hugo Eckener, of the Zeppelin Company before the Royal Aeronautical Society on March 26, was, perhaps, one of the most instructive which the members of that society have listened to for a very long time. Lieut.-Col. Tizard was in the chair. In his introduction the distinguished lecturer, who, it will be remembered, piloted the Z.R. Ill to America recently, referred to the old controversy : Airship versus aeroplane, and pointed out that the great strides made in the development of the latter had by no means resulted in the ousting of the former, but that the two have developed side by side, and that the airship has certain qualities which in some respects give it a superiority over the aeroplane. It could cover much greater distances ; it could reduce its speed to nil and still remain in the air ; it could travel and land in fogs, snowstorms and at night much more securely than the aeroplane ; and his personal opinion was that it was much easier to keep the airship aloft in stormy weather than was the case with the aeroplane. Dr. Eckener then gave a brief outline of the evolution of the Zeppelin airship up to the present, from which we quote the following : — " This evolution revolves in the main around two points : Firstly, speed; and, secondly, relative carrying power. Relative carrying power means, of course, the commercial carrying capacity by percentage with a given size of the ship, and provided that the ships are of an equal stability. As for the development of the speed which enabled the airships to con- quer strong winds and even storms, you are no doubt familiar with the decisive part that the development of the motor has played in this respect. Suffice it to point to the fact that Count Zeppelin had in his first airship, in 1900, a motor of 15 h.p., which weighed 480 kg. ; that in his second airship, in 1905, he had a motor of 80 h.p., also weighing 480 kg. ; and that the last motors during the War were 260 h.p. with almost exactly the same weight." The lecturer then referred briefly to the improvement in shape which took place, and which changed the airship hull from the plain cylinder with rounded ends and multi-rudder control organs to the streamline form of the modern airship, with cantilever monoplane tail surfaces. How this improve- ment in form assisted in an increase in speed was told by the lecturer as follows :— " The speed attained by those types (i.e., the earlier air- ships) up to the time of the beginning of the War amounted at the most to about 18 m.s. (40 m.h.), and the relative commercial carrying lift was about 25 per cent, of the total lift. When you consider that the Z.R. Ill has a speed of 36 m.s. (80 m.h.) with a useful lift of 56 per cent, of the total lift, the immense progress made since those Zeppelin pioneers is evident. This progress is even more clearly demonstrated by the fact that Z.R. Ill, a ship of 70,000 cubic m., with an engine capacity of only 400 h.p., would have the same speed as the last pre-War airship of 18,000 cubic m., with 500 h.p., namely, 18 m.s., and that under this hypothesis its relative capacity would be 65 per cent., as against 25 per cent, of the last pre-War ship." The earlier ships were too slow (about 40 m.p.h.) for regular air traffic, but the lecturer pointed out that the five pre-War airships built for carrying passengers made altogether something like 2,000 nights and carried a total of 42,000 occupants without a single mishap to a passenger. This, it should be remembered, was before the War. Concerning the increase in size, the lecturer said :— " The systematic development of the Zeppelin airship, along more scientific lines, with a view to attaining the greatest possible capabilities, began shortly before the outbreak of the War and proceeded during the War with amazing rapiditv Since in the enlargement of the ship's size the required construction weights do not increase in the same measure as the contents, it is obvious that building larger ships offered the chance for an increase of its capabilities. Taking account of the military requirements for greater speed and greater ascending power to a maximum height, the size quickly grew from a good 20,000 cubic m. at the beginning of the War to a 32,000 and 36,000 cubic m. in 1915, to 56,000 cubic m. in 1916, and, finally, to almost 70,000 cubic m. in 1918. Meanwhile, there ran parallel with this development of speed an improvement of the shape which became more and more feasible with the increasing size. This improvement affected not only the ship's body itself, but primarily also the gondolas as well as the ship's entire organism. At the same time the constructors also were busily engaged in the work of removing or reducing all incidental resistance. Thus was gradually developed the so-called streamline form—a compact, smooth, cigar-shaped bag, in the construction of which special pains were taken to avoid as much as possible all outstanding wirework or other impeding objects protruding from the surface of the vessel. " Wyhile the improvements I have spoken of benefited primarily the speed of the airship, the engineers continued their unceasing efforts to reduce the weight of the ship's body itself, and thus to increase the useful lift. This they accomplished by perfecting the basic mathematical figuration of the ship's framework, utilising in this work the innumerable wartime experiences and lessons with regard to safety and intactness with a minimum of material. The airship was forced to keep pace in this respect with the airplane. " What was the result of all these efforts and improve- ments ? " The military airships at the beginning of the War had, with a size of about 22,000 cubic m. and with three motors of a total capacity of 630 h.p., a speed of 18 m.s ; they had, with a weight of 3,000 kg., an ascending power up to about 2,000 to 2,500, according to the temperature conditions, "In 1915 there was created a type of 32,000 cubic m., with four motors of altogether 960 h.p. It attained a speed of 25 m.s. and an ascending power up to 3,000 to 3,200 m. with a weight of 3,000 kg: This type was later made longer and brought up to a size of 36,000 cubic m., whereby the ascending power grew by 300 m. without the speed being noticeably reduced. " But the rapid development of the airplane made it necessary, even in 1916, to bring out a considerably larger and more capable type of airship. It was a vessel of 56,000 cubic m. contents with six motors, and which had 28-5 m. speed, and an ascending power to about 4,000 m. with 7,000 kg. weight. However, this ship came out at a time when the phosphorus igniting missiles for the defence against airships had been introduced, which made the use of this type impossible. A greater ascending power had to be attained. The weight reduction required for this was reached by building out one of the motors and other important alterations in the construction, especially as regards the machine, the engine gondolas, and the transference of power. These alterations in construction were also designed to reduce the incidental resistance. The reconstruction showed the really astonishing result that the speed was increased from 28-5 m. to 31 m. per second, and that at the same time the maximum ascending power was gradually increased from 4,000 m. to 5,500 m. with 7,000 kg. of load. The useful lift had been increased from 45 per cent, to 65 per cent of the total lift. This type represented in point of construction probably the best attained during the War. An increase of the size to 68,000 cubic m. through the addition of two gas compartments, with equal diameter and with a simultaneous increase of the number of motors to seven, brought no essential improvement. Improvements worth while were not attained until after the War, especially with the Z.R.III., which I shall discuss later." A series of lantern slides was then shown, illustrating the points dealt with by Dr. Eckener in the preceding paragraphs of his paper. Turning to the post-War experience of the Zeppelin Company, Dr. Eckener said :— "Only three airships were built after the War—the Bodensee, the Nordstern, and Z.R.III. The first two had been designed for traffic between Berlin and Friedrichshafen, but only the Bodensee was actually used in this traffic from the end of August until December, 1919, because these trips had to be discontinued by order of the Ambassadors' Conference. The results of the trial service had been extraordinarily satisfactory. The trips could be carried out in almost any kind of weather, and no mishap occurred unless an emergency landing in the open field during a heavy snowstorm is to be characterised as such—a landing which, by the way, caused no damage to either passengers or ship. The Bodensee was always occupied to its capacity, and it made altogether 103 trips, on which it carried a total of 2,450 passengers. " The Bodensee had a gas capacity of only 20,000 cubicjm., and was equipped with four engines of 260 h.p. each, which gave the ship a speed of 36-3 m.s. It had a useful lift of 9,600 kg., or 42 per cent, of the total lift. If you compare this with the last passenger airship before the War which, with the same cubic capacity, had a useful lift of only 6.500 kg. 202
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