With each variant operating ever further afield, the Type IX was a most successful design. Shown is the ‘B’ variant U-106, which was particularly successful in the North Atlantic, off the American eastern seaboard, in the Caribbean and off West Africa. She also torpedoed the battleship Malaya.
The Type IX class was designed for ocean warfare. Loosely based on the far smaller Type II, it differed fundamentally in having a double hull. This feature increased useful internal volume by enabling fuel and ballast tanks to be sited externally, in turn; the extra hull improved survivability by cushioning the inner (pressure) hull from explosive shock and gave the boats greatly improved seakindliness on the surface. Habitability was improved for operations of longer duration and the number of torpedoes carried, at 22, was about 50 per cent more than those of a Type VIIC. The deck gun was increased in calibre from 88 to 105mm (3.465 to 4.13m).
To give an idea of how designs developed during the course of the war, the Type IXA and Type VIIA variants were, respectively, 76.5 and 64,5m (251 and 211.6ft) long, while the final Type IXD and Type VIIF marks, were 87.5 and 77.6m (287.07 and 254.6ft) long.
The major objective with the Type IX variants was to improve range rather than offensive capability. Thus the eight Type IXA boats could achieve 19500 km (12,120 miles) on the surface at 10 kts yet, even before September 1939, were being complemented by the first of 14 Type IXB boats capable of 22250km (13,825 miles). These were followed by the largest group, the Type IXC and slightly modified Type IXC-40, 149 boats with bunkers for 25000km (15,535 miles).
From the opening of hostilities, the Type IXs worked the western and southern Atlantic and, on the entry into the war of the United States, were supplemented by Type VIICs for the ‘Happy Time’, ravaging shipping down the USA’s eastern seaboard to the Caribbean before a proper convoy system had been instituted.
As early as 1940, the Type IXD was on the board, with an extra 10.8-m (35.4-ft) section worked in. Two examples of the Type IXD1 were built, with no armament, but capable of stowing over 250 tons of fuel for the topping-up of other boats. The 29 Type IXD2s boats were operational boats with the phenomenal range of 58400 km (36,290 miles), enabling them to work the Indian Ocean and even reach Japan.
The longest patrol by a U-boat during the war was by U196 a type IXD2 U Cruiser commanded by Knights Cross holder Friedrich Kentrat. It went from the 13 March 1943 to the 23 October 1943 a huge 225 days or 32.1 Weeks. He only sank 2 ships for 12,285 tons in this time.
Some Type IXD2s included a small, single-seat towed gyro kite to increase their visual search radius. The Type IXD2 was further refined to the Type IXD2-42, but only one of this variant was ever completed. Advanced diesels in the Type IXD Is gave a 21-kt surface speed, but were found unreliable and not repeated.
Type: ocean-going submarine
Displacement: 1,120 tons surfaced and 1,232 tons submerged
Dimensions: length 76.70 m (251 ft 8 in); beam 6.75 m (22 ft 2 in); draught 4.70 m (15 ft 5 in)
Propulsion: surfaced diesels delivering 4,400 hp (3281 kW) and submerged electric motors delivering 1,000 hp (746 kW) to two shafts
Speed: surfaced 18.2 kts and submerged 7.5 kts
Range: surfaced 25000 km (15,535 miles) at 10 kts and submerged 115 km (71.5 miles) at 4 kts
Armament: one 105-mm (4.13-in) gun, one 37-mm AA gun, one 20-mm AA gun, and six 533-mm (21 -in) torpedo tubes (four forward and two aft) with 22 torpedoes