©Bernulius/stock.adobe.com

Lightweight Garage #14 The last great German zeppelin

January 20, 2022
by Florian Gabel

The Vehicle

At the beginning of the 20th century, aviation was still in its infancy and aircraft like the thousands flying around the globe today were still unimaginable. The first airplanes were often built mainly of wood, struts, tension wires and canvas and were rather small. At the same time, airships were developed, which can be divided into three categories.

Blimps, where the hull is held in shape by positive pressure and to which the nacelle and tail unit are directly attached.

Rigid airships, which are built like a ship, with a keel and a fixed framework, which is wrapped in fabric panels and receives its lift from lifting gas cells.

Semi-rigid airships, which in addition to a bulging hull, have a supporting structure on the underside. The engines, nacelle and tail unit are attached there.

LZ 130 Graf Zeppelin II was the last German rigid airship and was designed for Atlantic crossings and voyages to the tropics. Its frame was made of duralumin and its hull was made of linen cloth, which was given various coatings to protect it from the elements. The aluminum powder added to the paint for thermal protection, gave the airships their characteristic silver color. LZ 130 Graf Zeppelin II had 16 lifting gas cells, which were originally to be filled with helium, but the USA refused to supply this gas and so hydrogen was used, despite its danger. To avoid an accident like that of LZ 129 Hindenburg at Lakehurst, the connections between the hull and the supporting structure were coated with a conductive coating of graphite.

The lifting gas cells, and the rigid hull made possible the luxurious furnishings inside the airship. On board were lounges, washrooms, a dining room, double cabins for 40 guests, and other rooms for crew accommodation, luggage, and airship operations. It was powered by four 16-cylinder Daimler Benz diesel engines and propellers. The continuous power of the engines was 799 hp and the maximum power was 999 hp.

Although designed for voyages to distant countries, LZ 130 Graf Zeppelin II was mainly used within Germany and completed 30 voyages.

The era of the great German airships ended before the end of World War II and LZ 130 Graf Zeppelin II was scrapped, under political pressure, in 1940 along with other airships. Today, airships are mainly used for tourist purposes.

Airship LZ 130 Graf Zeppelin II – Basic data

Quelle: LZ 130

Commissioning1938
Length245 m
Diameter41.2 m
Volume200,000 m³
Empty weight114 t
Payload105 t
Carrying capacity70 t Hydrogen/50 t Helium
Vmax135 km/h
Range12,000 km


Unknown author, Flying Zeppelin, Public Domain

The Technology

At the beginning of the 20th century, Alfred Wilm experimented with producing various particularly strong aluminum alloys. He applied standard steel production processes to various aluminum alloys. He found that the alloys exhibited greater strength and hardness after quenching and after a resting period of several days. This is mainly since some time after quenching, an initially suppressed precipitation of a second phase, a homogeneous chemical compound of two metals, in this case between copper and aluminum, takes place in the alloy. This can take place by cold aging (room temperature) or artificial aging (higher temperatures).

Wilm's alloy contained small amounts of copper, magnesium, manganese, silicon, and iron in addition to the aluminum. Because of its strength, the new alloy was called duralumin. Today's higher-strength aluminum alloys are trivially also often still called this or similar and are widely used in various industries.

The lightweight construction and weight management aspect

As can be seen from the table, duralumin has more than half the density of simple steels. Therefore, more than half of the weight could be saved in the skeleton. Most importantly, duralumin has a very similar tensile strength to simple steels.

Compared materials

Source

Material Density
[kg/dm³]
E-Modulus
[N/mm²]
Tensile strength
[N/mm²]
Dural AlCU4Mg12.75-2.8773,000420-500
Pure aluminium Al99.52.770,00075-100
Carbon steel S3557.9200,000510
Chrom-Nickel steel7.9200,000500-750
Spring steel 54SiCr67.46210,0001450-1750

This allowed the use of the large scaffolds that formed the support structure of the rigid airships. A military airship, LZ 26, was the first German zeppelin whose basic structure was built of duralumin.


Stahlkocher, Structure of a zeppelin made of duralumin, CC BY-SA 3.0

Illustration of LZ 130 Graf Zeppelin II

In addition, LZ 130 Graf Zeppelin II was the first zeppelin to have a ballast water extraction system to compensate for the loss of weight due to fuel consumption during the voyage. The water was obtained by condensation from the exhaust gases of the diesel engines. The water vapor produced during combustion was captured and cooled. The water thus obtained was fed into the ballast water tanks. In some cases, such ballast water was also filled by precipitation on the hull or by water intake from the sea, lakes, or rivers. However, the use of the ballast extraction system was much more reliable and independent of weather conditions.

 

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