from Zeppelin's only serious competitor, the Mannheim-based Schütte-Lanz company. While their dirigibles were never as successful, Professor Schütte's more scientific approach to airship design led to important innovations including the streamlined hull shape, the simpler cruciform fins (replacing the more complicated box-like arrangements of older Zeppelins), individual direct-drive engine cars, anti-aircraft machine-gun positions, and gas ventilation shafts which transferred vented hydrogen to the top of the airship. New production facilities were set up to assemble Zeppelins from components fabricated in Friedrichshafen. The pre-war M-class designs were quickly enlarged, to produce the long duralumin P-class, which increased gas capacity from to , introduced a fully enclosed gondola and had an extra engine. These modifications added to the maximum ceiling, around 9 km/h (6 mph) to the top speed, and greatly increased crew comfort and hence endurance. Twenty-two P-class airships were built; the first, LZ 38, was delivered to the Army on 3 April 1915. The P class was followed by a lengthened version, the Q class. In July 1916 Luftschiffbau Zeppelin introduced the R-class, 199.49 m (644 ft 8 in) long, and with a volume of . These could carry loads of three to four tons of bombs and reach speeds of up to , powered by six Maybach engines. In 1917, following losses to the air defences over Britain, new designs were produced which were capable of flying at much higher altitudes, typically operating at around . This was achieved by reducing the weight of the airship by reducing the weight of the structure, halving the bomb load, removing the defensive armament and by reducing the number of engines to five. However these were not successful as bombers: the greater height at which they operated greatly hindered navigation, and their reduced power made them vulnerable to unfavorable weather conditions. At the beginning of the war Captain Ernst A. Lehmann and Baron Gemmingen, Count Zeppelin's nephew, developed an observation car for use by dirigibles. This was equipped with a wicker chair, chart table, electric lamp and compass, with telephone line and lightning conductor part of the suspension cable. The car's observer would relay navigation and bomb dropping orders to the Zeppelin flying within or above the clouds, so remaining invisible from the ground. Although used by Army airships, they were not used by the Navy, since Strasser considered that their weight meant an unacceptable reduction in bomb load. End of the