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 alt.i.tude 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.

[PLATE 24: Zeppelin-Werke Staaken "Giant" All Metal Monoplane.

Which carried eighteen pa.s.sengers in a luxurious cabin at a speed of 145 miles per hour. Power plant consists of 4-260 horsepower Maybach Motors totaling more than 1000 H. P.

Zeppelin-Dornier "Dragon Fly" All Metal Flying Boat, 1921.

Carries pilot and two pa.s.sengers with 60 horsepower motor at a speed of 80 miles per hour and a gasoline consumption of only four gallons per hour.]

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:

1914 1915 1916 1917 1918 Total

At Friedrichshafen 6 19 14 14 8 59 At Potsdam 1 7 8 - - 16 At Staaken - - 2 9 1 12 At Frankfort on Main 1 .. .. .. .. 1 __ __ __ __ __ __ Total 8 26 24 23 9 88

[PLATE 25: Zeppelin-Dornier "Dragon Fly" All Metal Flying Boat, 1921.

Wing span, 28 feet, weight empty 858 pounds. Water tight bulkheads are provided in-side fins and wings.

Zeppelin-Dornier "Dragon Fly" All Metal Flying Boat, 1921.

With wings folded greatest width is only 10 feet.]

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 pa.s.sengers. 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 a.n.a.lysis 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 unsurpa.s.sed, 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.

[PLATE 26: Zeppelin-Dornier "Dolphin" Monoplane All Metal Flying Boat Type DoCsII, 1920 Model.

Zeppelin-Dornier "Dolphin" Monoplane All Metal Flying Boat Type DoCsII, 1921 Model.

Carries six pa.s.sengers besides pilot and mechanician. Speed 93 miles per hour, 185 horsepower motor. Gasoline consumption 11.9 gallons per hour. Weight empty 3200 pounds.]

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.

[PLATE 27: Zeppelin-Dornier "Komet" All Metal Monoplane, Type DoCIII, 1920 Model.

Zeppelin-Dornier "Komet" All Metal Monoplane.

Carries six pa.s.sengers besides pilot and mechanician. One motor of 185 horsepower.]

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

===========+=======================+========+========+======+======+===== | | | | Efficiency | |Capacity|Maximum +------+------+----- Nationality| Type and Name | Cubic | Speed, | | | | | Meters | Miles |Speed | Lift |All- | | | per | | |round | | | Hour | (1) | (2) |(3) -----------+-----------------------+--------+--------+------+------+----- Non-Rigid Airships -----------+-----------------------+--------+--------+------+------+----- American | Goodyear Pony Blimp | 990 | 40 | 24.2 | 0.60 | 15 French | Caussin T 2 | 9120 | 57.5 | 28.0 | 0.85 | 24 British | NS | 10200 | 57.2 | 25.6 | 0.65 | 17 German | PL27 | 31300 | 55.7 | 27.0 | 0.98 | 26 Italian | T 34 (Roma) | 34000 | 74.2 | 21.5 | 0.68 | 15 -----------+-----------------------+--------+--------+------+------+----- Rigid Airships -----------+-----------------------+--------+--------+------+------+----- British | R 80 | 34000 | 59.7 | 36.6 | 0.80 | 29 British | R 33-R 34 | 55500 | 59.7 | 37.3 | 0.75 | 28 British | R 36-R 37 | 59500 | 65.0 | 40.0 | 0.80 | 32 German | Schutte-Lanz SL22 | 56000 | 62.5 | 45.2 | 1.36 | 61 -----------+-----------------------+--------+--------+------+------+----- German | Zeppelin LZ 120 | | | | | | (Bodensee) | 20000 | 82 | 63.7 | 0.76 | 48 German | Zeppelin LZ 121 | | | | | | (Nordstern) | 22500 | 78.8 | 61.4 | 0.78 | 48 German | Zeppelin LZ 100 | 56000 | 67.2 | 56.0 | 1.59 | 89 German | Zeppelin LZ 113 | 62200 | 81 | 62.2 | 1.60 | 100 German | Zeppelin LZ 102 | 68500 | 63.7 | 54.4 | 1.90 | 103 -----------+-----------------------+--------+--------+------+------+------

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

[PLATE 28: Dr. Max Freiherr von Gemmingen.

Dr. Hugo Eckener

Kommerzienrat Alfred Colsman

Dr. Ing. Ludwig Durr