A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, a fluid is accelerated behind the blade. Propeller dynamics, like those of aircraft wings, can be modelled by Bernoulli's principle and Newton's third law. Most marine propellers are screw propellers with fixed helical blades rotating around a horizontal axis or propeller shaft; the principle employed in using a screw propeller is used in sculling. It is part of the skill of propelling a Venetian gondola but was used in a less refined way in other parts of Europe and elsewhere. For example, propelling a canoe with a single paddle using a "pitch stroke" or side slipping a canoe with a "scull" involves a similar technique. In China, called "lu", was used by the 3rd century AD. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at the effective angle.
The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade, but in practice there are nearly always more than one so as to balance the forces involved; the origin of the screw propeller starts with Archimedes, who used a screw to lift water for irrigation and bailing boats, so famously that it became known as Archimedes' screw. It was an application of spiral movement in space to a hollow segmented water-wheel used for irrigation by Egyptians for centuries. Leonardo da Vinci adopted the principle to drive his theoretical helicopter, sketches of which involved a large canvas screw overhead. In 1661, Toogood and Hays proposed using screws for waterjet propulsion, though not as a propeller. Robert Hooke in 1681 designed a horizontal watermill, remarkably similar to the Kirsten-Boeing vertical axis propeller designed two and a half centuries in 1928. In 1752, the Academie des Sciences in Paris granted Burnelli a prize for a design of a propeller-wheel.
At about the same time, the French mathematician Alexis-Jean-Pierre Paucton, suggested a water propulsion system based on the Archimedean screw. In 1771, steam-engine inventor James Watt in a private letter suggested using "spiral oars" to propel boats, although he did not use them with his steam engines, or implement the idea; the first practical and applied use of a propeller on a submarine dubbed Turtle, designed in New Haven, Connecticut, in 1775 by Yale student and inventor David Bushnell, with the help of the clock maker and brass foundryman Isaac Doolittle, with Bushnell's brother Ezra Bushnell and ship's carpenter and clock maker Phineas Pratt constructing the hull in Saybrook, Connecticut. On the night of September 6, 1776, Sergeant Ezra Lee piloted Turtle in an attack on HMS Eagle in New York Harbor. Turtle has the distinction of being the first submarine used in battle. Bushnell described the propeller in an October 1787 letter to Thomas Jefferson: "An oar formed upon the principle of the screw was fixed in the forepart of the vessel its axis entered the vessel and being turned one way rowed the vessel forward but being turned the other way rowed it backward.
It was made to be turned by the hand or foot." The brass propeller, like all the brass and moving parts on Turtle, was crafted by the "ingenious mechanic" Issac Doolittle of New Haven. In 1785, Joseph Bramah in England proposed a propeller solution of a rod going through the underwater aft of a boat attached to a bladed propeller, though he never built it. In 1802, Edward Shorter proposed using a similar propeller attached to a rod angled down temporarily deployed from the deck above the waterline and thus requiring no water seal, intended only to assist becalmed sailing vessels, he tested it on the transport ship Doncaster in Gibraltar and at Malta, achieving a speed of 1.5 mph. The lawyer and inventor John Stevens in the United States, built a 25-foot boat with a rotary stem engine coupled to a four-bladed propeller, achieving a speed of 4 mph, but he abandoned propellers due to the inherent danger in using the high-pressure steam engines, instead built paddle-wheeled boats. By 1827, Czech-Austrian inventor Josef Ressel had invented a screw propeller which had multiple blades fastened around a conical base.
He had tested his propeller in February 1826 on a small ship, manually driven. He was successful in using his bronze screw propeller on an adapted steamboat, his ship, Civetta of 48 gross register tons, reached a speed of about 6 knots. This was the first ship driven by an Archimedes screw-type propeller. After a new steam engine had an accident his experiments were banned by the Austro-Hungarian police as dangerous. Josef Ressel was at the time a forestry inspector for the Austrian Empire, but before this he received an Austro-Hungarian patent for his propeller. He died in 1857; this new method of propulsion was an improvement over the paddlewheel as it was not so affected by either ship motions or changes in draft as the vessel burned coal. John Patch, a mariner in Yarmouth, Nova Scotia developed a two-bladed, fan-shaped propeller in 1832 and publicly demonstrated it in 1833, propelling a row boat across Yarmouth Harbour and a small coastal schooner at Saint John, New Brunswick, but his patent application in the United States was rejected until 1849 because he was not an American citizen.
His efficient design drew praise in American scientific circles but by
Ultra was the designation adopted by British military intelligence in June 1941 for wartime signals intelligence obtained by breaking high-level encrypted enemy radio and teleprinter communications at the Government Code and Cypher School at Bletchley Park. Ultra became the standard designation among the western Allies for all such intelligence; the name arose because the intelligence thus obtained was considered more important than that designated by the highest British security classification used and so was regarded as being Ultra secret. Several other cryptonyms had been used for such intelligence; the code name Boniface was used as a cover name for Ultra. In order to ensure that the successful code-breaking did not become apparent to the Germans, British intelligence created a fictional MI6 master spy, who controlled a fictional series of agents throughout Germany. Information obtained through code-breaking was attributed to the human intelligence from the Boniface network; the U. S. used the codename Magic for its decrypts from Japanese sources including the so-called "Purple" cipher.
Much of the German cipher traffic was encrypted on the Enigma machine. Used properly, the German military Enigma would have been unbreakable; the term "Ultra" has been used synonymously with "Enigma decrypts". However, Ultra encompassed decrypts of the German Lorenz SZ 40/42 machines that were used by the German High Command, the Hagelin machine. Many observers, at the time and regarded Ultra as immensely valuable to the Allies. Winston Churchill was reported to have told King George VI, when presenting to him Stewart Menzies: "It is thanks to the secret weapon of General Menzies, put into use on all the fronts, that we won the war!" F. W. Winterbotham quoted the western Supreme Allied Commander, Dwight D. Eisenhower, at war's end describing Ultra as having been "decisive" to Allied victory. Sir Harry Hinsley, Bletchley Park veteran and official historian of British Intelligence in World War II, made a similar assessment of Ultra, saying that while the Allies would have won the war without it, "the war would have been something like two years longer three years longer four years longer than it was."
However and others have emphasized the difficulties of counterfactual history in attempting such conclusions, some historians have said the shortening might have been as little as the three months it took the United States to deploy the atomic bomb. The existence of Ultra was kept secret for many years after the war. After it was revealed in the middle 1970s, historians have altered the historiography of World War II. For example, Andrew Roberts, writing in the 21st century, states, "Because he had the invaluable advantage of being able to read Rommel's Enigma communications, Montgomery knew how short the Germans were of men, ammunition and above all fuel; when he put Rommel's picture up in his caravan he wanted to be seen to be reading his opponent's mind. In fact he was reading his mail." Over time, Ultra has become embedded in the public consciousness and Bletchley Park has become a significant visitor attraction. As stated by historian Thomas Haigh, "The British code-breaking effort of the Second World War secret, is now one of the most celebrated aspects of modern British history, an inspiring story in which a free society mobilized its intellectual resources against a terrible enemy."
Most Ultra intelligence was derived from reading radio messages, encrypted with cipher machines, complemented by material from radio communications using traffic analysis and direction finding. In the early phases of the war during the eight-month Phoney War, the Germans could transmit most of their messages using land lines and so had no need to use radio; this meant that those at Bletchley Park had some time to build up experience of collecting and starting to decrypt messages on the various radio networks. German Enigma messages were the main source, with those of the Luftwaffe predominating, as they used radio more and their operators were ill-disciplined. "Enigma" refers to a family of electro-mechanical rotor cipher machines. These produced a polyalphabetic substitution cipher and were thought to be unbreakable in the 1920s, when a variant of the commercial Model D was first used by the Reichswehr; the German Army, Air Force, Nazi party and German diplomats used Enigma machines in several variants.
Abwehr used a four-rotor machine without a plugboard and Naval Enigma used different key management from that of the army or air force, making its traffic far more difficult to cryptanalyse. The commercial versions were not as secure and Dilly Knox of GC&CS, is said to have broken one before the war. German military Enigma was first broken in December 1932 by the Polish Cipher Bureau, using a combination of brilliant mathematics, the services of a spy in the German office responsible for administering encrypted communications, good luck; the Poles read Enigma in France. At the turn of 1939, the Germans made the systems ten times more complex, which required a tenfold increase in Polish decryption equipment, which they could not meet. On 25 July 1939, the Polish Cipher Bureau handed reconstructed Enigma machines and their techniques for decrypting ciphers to the French and British. Gordon Welchman wrote, Ultra would never have got off the ground if we had not
Caterpillar Energy Solutions
Caterpillar Energy Solutions GmbH MWM GmbH and Deutz Power Systems, is a mechanical engineering company based in Mannheim, Baden-Württemberg, Germany. For many years it was known as Motoren-Werke Mannheim. In 2009 the company was the third-largest producer by revenue of diesel engines; the main focus of production is gensets for the generation of electrical energy from 400 to 4,300 kWel per unit. It provides consulting and engineering, construction and commissioning of plants as well as global aftersales service; the company has its own training center. In 1922 the department for the construction of stationary engines was outsourced and had its name changed from Benz & Cie. Rheinische Gasmotorenfabrik in Mannheim to Motorenwerke Mannheim; the renowned German engineer Prosper L'Orange, a pioneer of diesel engine technology, was the technical manager then. Before that he worked for Benz & Cie; the construction of diesel engines in particular used to be the core business of MWM, amongst others for utility vehicles and agricultural machines.
In 1924 MWM manufactured their first tractor, called Motorpferd. In 1931, tractor production was discontinued. For quite a long time, combines by Claas, tractors by the French manufacturer Renault, by the German companies Fendt, Bautz and Ritscher, were equipped with MWM engines. In 1926 Knorr-Bremse AG took over. In 1985 they sold MWM to Deutz AG; the company's site was maintained. The company, along with MAN SE, remained the chief engine manufacturer in the field of commercial diesel engines in Germany. DEUTZ expanded the gas engine division. In August 2007, DEUTZ sold the engine company to the financial investor 3i as Deutz Power Systems for 360 million euros. On 1 October 2008 Deutz Power Systems was renamed MWM GmbH. Today MWM offers gas engines for cogeneration units and biogas plants with an output between 400 and 4,300 kilowatts. To a smaller extent diesel engines are still produced. On 22 October 2010 Caterpillar Inc. announced an agreement with 3i regarding the acquisition of MWM for 580 million euros.
Subject to the consent of prudential authorities MWM will become part of Caterpillar`s Electric Power Division. On 8 October MWM announced that it would change its name to Caterpillar Energy Solutions from 1 November 2013. Official website Documents and clippings about Caterpillar Energy Solutions in the 20th Century Press Archives of the German National Library of Economics
Nazi Germany is the common English name for Germany between 1933 and 1945, when Adolf Hitler and his Nazi Party controlled the country through a dictatorship. Under Hitler's rule, Germany was transformed into a totalitarian state that controlled nearly all aspects of life via the Gleichschaltung legal process; the official name of the state was Deutsches Reich until 1943 and Großdeutsches Reich from 1943 to 1945. Nazi Germany is known as the Third Reich, meaning "Third Realm" or "Third Empire", the first two being the Holy Roman Empire and the German Empire; the Nazi regime ended. Hitler was appointed Chancellor of Germany by the President of the Weimar Republic, Paul von Hindenburg, on 30 January 1933; the NSDAP began to eliminate all political opposition and consolidate its power. Hindenburg died on 2 August 1934 and Hitler became dictator of Germany by merging the offices and powers of the Chancellery and Presidency. A national referendum held 19 August 1934 confirmed Hitler as sole Führer of Germany.
All power was centralised in Hitler's person and his word became the highest law. The government was not a coordinated, co-operating body, but a collection of factions struggling for power and Hitler's favour. In the midst of the Great Depression, the Nazis restored economic stability and ended mass unemployment using heavy military spending and a mixed economy. Extensive public works were undertaken, including the construction of Autobahnen; the return to economic stability boosted the regime's popularity. Racism antisemitism, was a central feature of the regime; the Germanic peoples were considered by the Nazis to be the master race, the purest branch of the Aryan race. Discrimination and persecution against Jews and Romani people began in earnest after the seizure of power; the first concentration camps were established in March 1933. Jews and others deemed undesirable were imprisoned, liberals and communists were killed, imprisoned, or exiled. Christian churches and citizens that opposed Hitler's rule were oppressed, many leaders imprisoned.
Education focused on racial biology, population policy, fitness for military service. Career and educational opportunities for women were curtailed. Recreation and tourism were organised via the Strength Through Joy program, the 1936 Summer Olympics showcased Germany on the international stage. Propaganda Minister Joseph Goebbels made effective use of film, mass rallies, Hitler's hypnotic oratory to influence public opinion; the government controlled artistic expression, promoting specific art forms and banning or discouraging others. The Nazi regime dominated neighbours through military threats in the years leading up to war. Nazi Germany made aggressive territorial demands, threatening war if these were not met, it seized Austria and Czechoslovakia in 1938 and 1939. Germany signed a non-aggression pact with the USSR, invaded Poland on 1 September 1939, launching World War II in Europe. By early 1941, Germany controlled much of Europe. Reichskommissariats took control of conquered areas and a German administration was established in the remainder of Poland.
Germany exploited labour of both its occupied territories and its allies. In the Holocaust, millions of Jews and other peoples deemed undesirable by the state were imprisoned, murdered in Nazi concentration camps and extermination camps, or shot. While the German invasion of the Soviet Union in 1941 was successful, the Soviet resurgence and entry of the US into the war meant the Wehrmacht lost the initiative on the Eastern Front in 1943 and by late 1944 had been pushed back to the pre-1939 border. Large-scale aerial bombing of Germany escalated in 1944 and the Axis powers were driven back in Eastern and Southern Europe. After the Allied invasion of France, Germany was conquered by the Soviet Union from the east and the other Allies from the west, capitulated in May 1945. Hitler's refusal to admit defeat led to massive destruction of German infrastructure and additional war-related deaths in the closing months of the war; the victorious Allies initiated a policy of denazification and put many of the surviving Nazi leadership on trial for war crimes at the Nuremberg trials.
The official name of the state was Deutsches Reich from 1933 to 1943 and Großdeutsches Reich from 1943 to 1945, while common English terms are "Nazi Germany" and "Third Reich". The latter, adopted by Nazi propaganda as Drittes Reich, was first used in Das Dritte Reich, a 1923 book by Arthur Moeller van den Bruck; the book counted the Holy Roman Empire as the German Empire as the second. Germany was known as the Weimar Republic during the years 1919 to 1933, it was a republic with a semi-presidential system. The Weimar Republic faced numerous problems, including hyperinflation, political extremism, contentious relationships with the Allied victors of World War I, a series of failed attempts at coalition government by divided political parties. Severe setbacks to the German economy began after World War I ended because of reparations payments required under the 1919 Treaty of Versailles; the government printed money to make the payments and to repay the country's war debt, but the resulting hyperinflation led to inflated prices for consumer goods, economic chaos, food riots.
When the government defaulted on their reparations payments in January 1923, French troops occupied German industrial areas along the Ruhr and widespread civil unrest followed. The National Socialist German Workers' Party (National
Kiel is the capital and most populous city in the northern German state of Schleswig-Holstein, with a population of 249,023. Kiel lies 90 kilometres north of Hamburg. Due to its geographic location in the north of Germany, the southeast of the Jutland peninsula and the southwestern shore of the Baltic Sea, Kiel has become one of the major maritime centres of Germany. For instance, the city is known for a variety of international sailing events, including the annual Kiel Week, the biggest sailing event in the world; the Olympic sailing competitions of the 1936 and the 1972 Summer Olympics were held in the Bay of Kiel. Kiel has been one of the traditional homes of the German Navy's Baltic fleet, continues to be a major high-tech shipbuilding centre. Located in Kiel is the GEOMAR - Helmholtz Centre for Ocean Research Kiel at the University of Kiel. Kiel is an important sea transport hub, thanks to its location on the Kiel Fjord and the busiest artificial waterway in the world, Kiel Canal. A number of passenger ferries to Sweden, Norway and other countries operate from here.
Moreover, today Kiel Harbour is an important port of call for cruise ships touring the Baltic Sea. Kiel's recorded history began in the 13th century, but the city was a Danish village, in the 8th century; until 1864 it was administered by Denmark in personal union. In 1866 the city was annexed by Prussia and in 1871 it became part of Germany. Kiel was one of the founding cities of original European Green Regi51 Award in 2006. In 2005 Kiel's GDP per capita was €35,618, well above Germany's national average, 159% of the European Union's average; the city is home to the University of Kiel. Kiel Fjord and the village of Kiel was first settled by Vikings who wanted to colonise the land that they had raided, for many years they settled in German villages; this is evidenced by the architecture of the fjord. The city of Kiel was founded in 1233 as Holstenstadt tom Kyle by Count Adolf IV of Holstein, granted Lübeck city rights in 1242 by Adolf's eldest son, John I of Schauenburg. Being a part of Holstein, Kiel belonged to the Holy Roman Empire and was situated only a few kilometres south of the Danish border.
Kiel, the capital of the county of Holstein, was a member of the Hanseatic League from 1284 until it was expelled in 1518 for harbouring pirates. In 1431, the Kieler Umschlag was first held, which became the central market for goods and money in Schleswig-Holstein, until it began to lose significance from 1850 on, being held for the last time in 1900, until when it has been restarted; the University of Kiel was founded on 29 September 1665 by Christian Albert, Duke of Holstein-Gottorp. A number of important scholars, including Theodor Mommsen, Felix Jacoby, Hans Geiger and Max Planck, studied or taught there. From 1773 to 1864, the town belonged to the king of Denmark. However, because the king ruled Holstein as a fief of the Holy Roman Empire only through a personal union, the town was not incorporated as part of Denmark proper, thus Kiel belonged to Germany. Though the empire was abolished in 1806, the Danish king continued to rule Kiel only through his position as Duke of Holstein, which became a member of the German Confederation in 1815.
When Schleswig and Holstein rebelled against Denmark in 1848, Kiel became the capital of Schleswig-Holstein until the Danish victory in 1850. During the Second Schleswig War in 1864, Kiel and the rest of the duchies of Schleswig and Holstein were conquered by a German Confederation alliance of the Austrian Empire and the Kingdom of Prussia. After the war, Kiel was administered by both the Austrians and the Prussians, but the Austro-Prussian War in 1866 led to the formation of the Province of Schleswig-Holstein and the annexation of Kiel by Prussia in 1867. On 24 March 1865 King William I based Prussia's Baltic Sea fleet in Kiel instead of Danzig; the Imperial shipyard Kiel was established in 1867 in the town. When William I of Prussia became Emperor William I of the German Empire in 1871, he designated Kiel and Wilhelmshaven as Reichskriegshäfen; the prestigious Kiel Yacht Club was established in 1887 with Prince Henry of Prussia as its patron. Emperor Wilhelm II became its commodore in 1891.
Because of its new role as Germany's main naval base, Kiel quickly increased in size in the following years, from 18,770 in 1864 to about 200,000 in 1910. Much of the old town centre and other surroundings were levelled and redeveloped to provide for the growing city; the Kiel tramway network, opened in 1881, had been enlarged to 10 lines, with a total route length of 40 km, before the end of the First World War. Kiel was the site of the sailors' mutiny which sparked the German Revolution in late 1918. Just before the end of the First World War, the German fleet stationed at Kiel was ordered to be sent out on a last great battle with the Royal Navy; the sailors, who thought of this as a suicide mission which would have no effect on the outcome of the war, decided they had nothing to lose and refused to leave the safety of the port. The sailors' actions and the lack of response of the government to them, fuelled by an critical view of the Kaiser, sparked a revolution which caused the abolition of the monarchy and the creation of the Weimar Republic.
During the Second World War, Kiel remained one of the major naval bases and shipbuilding centres of the German Reich. There was a slave labour camp for the local industry; because of its status as a naval port and as production site for submarines, Kiel was bombed by the Allies d
The Diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression. Diesel engines work by compressing only the air; this increases the air temperature inside the cylinder to such a high degree that atomised Diesel fuel injected into the combustion chamber ignites spontaneously. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; the process of mixing air and fuel happens entirely during combustion, the oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; the Diesel engine has the highest thermal efficiency of any practical internal or external combustion engine due to its high expansion ratio and inherent lean burn which enables heat dissipation by the excess air.
A small efficiency loss is avoided compared with two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed Diesel engines can reach effective efficiencies of up to 55%. Diesel engines may be designed as either four-stroke cycles, they were used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in ships. Use in locomotives, heavy equipment and electricity generation plants followed later. In the 1930s, they began to be used in a few automobiles. Since the 1970s, the use of Diesel engines in larger on-road and off-road vehicles in the US has increased. According to Konrad Reif, the EU average for Diesel cars accounts for 50% of the total newly registered; the world's largest Diesel engines put in service are 14-cylinder, two-stroke watercraft Diesel engines. In 1878, Rudolf Diesel, a student at the "Polytechnikum" in Munich, attended the lectures of Carl von Linde.
Linde explained that steam engines are capable of converting just 6-10 % of the heat energy into work, but that the Carnot cycle allows conversion of all the heat energy into work by means of isothermal change in condition. According to Diesel, this ignited the idea of creating a machine that could work on the Carnot cycle. After several years of working on his ideas, Diesel published them in 1893 in the essay Theory and Construction of a Rational Heat Motor. Diesel was criticised for his essay, but only few found the mistake that he made. Diesel's idea was to compress the air so that the temperature of the air would exceed that of combustion. However, such an engine could never perform any usable work. In his 1892 US patent #542846 Diesel describes the compression required for his cycle: "pure atmospheric air is compressed, according to curve 1 2, to such a degree that, before ignition or combustion takes place, the highest pressure of the diagram and the highest temperature are obtained-that is to say, the temperature at which the subsequent combustion has to take place, not the burning or igniting point.
To make this more clear, let it be assumed that the subsequent combustion shall take place at a temperature of 700°. In that case the initial pressure must be sixty-four atmospheres, or for 800° centigrade the pressure must be ninety atmospheres, so on. Into the air thus compressed is gradually introduced from the exterior finely divided fuel, which ignites on introduction, since the air is at a temperature far above the igniting-point of the fuel; the characteristic features of the cycle according to my present invention are therefore, increase of pressure and temperature up to the maximum, not by combustion, but prior to combustion by mechanical compression of air, there upon the subsequent performance of work without increase of pressure and temperature by gradual combustion during a prescribed part of the stroke determined by the cut-oil". By June 1893, Diesel had realised his original cycle would not work and he adopted the constant pressure cycle. Diesel describes the cycle in his 1895 patent application.
Notice that there is no longer a mention of compression temperatures exceeding the temperature of combustion. Now it is stated that the compression must be sufficient to trigger ignition. "1. In an internal-combustion engine, the combination of a cylinder and piston constructed and arranged to compress air to a degree producing a temperature above the igniting-point of the fuel, a supply for compressed air or gas. See US patent # 608845 filed 1895 / granted 1898In 1892, Diesel received patents in Germany, the United Kingdom and the United States for "Method of and Apparatus for Converting Heat into Work". In 1894 and 1895, he filed patents and addenda in various
A submarine pen is a type of submarine base that acts as a bunker to protect submarines from air attack. The term is applied to submarine bases constructed during World War II in Germany and its occupied countries, which were known as U-boat pens. Among the first forms of protection for submarines were some open-sided shelters with partial wooden foundations that were constructed during World War I; these structures were built at the time when bombs were light enough to be dropped by hand from the cockpit. By the 1940s, the quality of aerial weapons and the means to deliver them had improved markedly; the mid-1930s saw. Various factions in the navy were convinced. A Royal Air Force raid on the capital in 1940 plus the occupation of France and Great Britain's refusal to surrender was enough to trigger a massive building programme of submarine pens and air raid shelters. By the autumn of 1940, construction of the "Elbe II" bunker in Hamburg and "Nordsee III" on the island of Heligoland was under way.
Others swiftly followed. It was soon realised that such a massive project was beyond the Kriegsmarine, the Todt Organisation was brought in to oversee the administration of labour; the local supply of such items as sand, aggregate and timber was a cause for concern. The steel required was imported from Germany; the attitudes of the people in France and Norway were different. In France there was no problem with the recruitment of men and the procurement of machinery and raw materials, it was a different story in Norway. There, the local population were far more reluctant to help the Germans. Indeed, most labour had to be brought in; the ground selected for bunker construction was no help either: being at the head of a fjord, the foundations and footings had to be hewn out of granite. Several metres of silt had to be overcome. Many of the workers needed were forced labour, most the concentration camp inmates supplied by the Schutzstaffel from camps near the pens; the incessant air raids caused serious disruption to the project, hampering the supply of material, destroying machinery, harassing the workers.
Machinery such as excavators, cranes and concrete pumps was temperamental, in the case of steam-driven equipment noisy. Bunkers had to be able to accommodate more than just U-boats. Storage space for spares, explosives and oil was required. Four types of bunker were constructed: Covered lockThese were bunkers built over an existing lock to give a U-boat some protection while it was at its most vulnerable – i.e. when the lock was emptying or filling. They were constructed with new locks alongside an existing structure. Construction bunkerUsed for building new boatsFitting-out bunkersAfter launch, many U-boats were fitted-out under their protectionShelter for operational boats and repair bunkersThis was the most numerous type. There were two types that were built either over the water; the former meant. Pumping the water out enabled dry dock repairs to be carried out; some bunkers were large enough to allow the removal of aerials. There is no truth in the rumour of an underground bunker on Fuerteventura in the Canary Islands.
This story was gleaned from a similar situation in Le Havre in France when captured U-boat men were interrogated by the British. Pens were constructed in many occupied countries. Pens protecting construction of the Type XXI submarine were located in Hamburg and Danzig; the "Hornisse" bunker was not started until 1944 in Bremen. Begun in 1943, it was built to be a manufacturing facility, where Type XXI submarines were to be constructed, it too was never completed. Post-war, it was used as a test site for British and American bombs before becoming a storage facility for the German Navy; the labour to construct it was supplied by local concentration camps such as Neuengamme in Hamburg. Valentin: 53°13′00″N 08°30′15″E Hornisse: 53°07′01.5″N 08°44′04″E Since it was out of range of Allied aircraft, no pens were built in Danzig. The city was the site of two structures, "Elbe II" and "Fink II"; the Finkenwerder bunker was constructed by 1,700 slave labourers over four years. After capture, it was demolished with 32 tonnes of bombs.
Elbe II: 53°31′43″N 09°57′08″E Fink II: 53.541°N 09.854°E / 53.541. It was left alone until near the end of the war when it was attacked by the RAF and like most of the facilities on the island destroyed, it was used after the end of the war for testing new weapons. No trace of the pen has survived. 54.177199°N 07.893521°E / 54.177199. They were started in 1941 and 1942 respec