Captain Jack (Updated: 4/14/2016):
The Type IX was derived from the World War I-era MS boats and was developed from the earlier Type IA class of 1934-1935. The new type was differentiated by its use of a double hull construction. The double hull construction allowed for greater internal capacities by positioning fuel stores and ballast tanks outside of the main hull and inside of a second watertight hull. Additionally, this hull design provided for greater survivability for the crew and ship structure alike, able to absorb potentially lethal explosive forces more efficiently. The design also made for a more robust performer when operating in the volatile surface elements. The Type IX saw her torpedo count increased to twenty-two, along with her six tubes, making her a lethal performer on any scale. Despite this offensive punch, the main goal in the Type IX design was in the improving of a U-boats operational range. The proceeding design success came at the cost of decreased maneuverability and increased dive times.
The Allies were making great use of the Atlantic Ocean waterways to shuffle troops, arms and supplies to Europe for use against German interests and both German leader Adolf Hitler and British Prime Minister Winston Churchill knew the value of winning the war along this front. Germany began developing long range submarines to counter the growing threat of American involvement in the war and developed such boats with enough endurance to spy on and engage vessels along the eastern coast of the United States.
From the start of the war, Type IXs were seen in action across the Atlantic and concentrated their efforts along the eastern seaboard of America as well as in actions in the south Atlantic. The main targets became the unprotected shipping that traversed the Atlantic and, at this time, had yet to incorporate suitable self-defense armament or become part of any concentrated convoy strategy. While finding successes in this venture, Type IXs were eventually replaced in this role by the Type VIIC class. Allied countermeasures improved substantially as the war progressed with the addition of radar and sonar systems as well as patrols by air becoming ever more common and concentrated, putting the U-boats on the defensive. Convoys and escorts also contributed to the many losses of U-boat crews by war's end.
The Type IX class as a whole sported a sleek, elongated and streamlined form consistent with the time. The fin was set approximately amidships with the deck gun positioned just forward of the tower (the gun sometimes omitted). The tower itself held the anti-aircraft armament to allow for quick reactions by the gunnery crew. Both of these emplacements were set in an aft-facing direction in trainable mounts. The sail was fitted with the applicable periscope and sighting fixtures. Vents dotted the long-running sides of the Type IX design. The upper surface of the hull was flat to allow for crew to traverse her topside while the sides bulged outwardly ever so slightly to incorporate the needed internal compartments. The design tapered into a streamlined spine along the bottom of the hull, suitable for cutting through the deep ocean water. The twin shafts were set to the stern, one system to either hull side, each capped with a three-bladed propeller. The rudder component was set under the stern and controlled the submarine's side-to-side maneuvering as required. Anchors were positioned along the bow sides. There were six total torpedo tube bays with four of these fitted along the bow sides and two in stern side positions. A snorkel allowed the Type IX to recharge her batteries while remaining submerged just under the surface of the water. The crew complement was made up of 48 personnel - four officers and forty-four Kriegsmarine sailors.
Armament (Type IXC) centered around the 533mm (21-inch) torpedo. Able to carry 22 of these and coupled with the Type IXs endurance, the vessel could stay in the field for long periods of time while locating and shadowing enemy convoys and ships, striking at the most opportune time (along the surface, usually at night). Six reload torpedoes were held internally with the rest held in external torpedo "carriers" - two such provisions mounted to the bow and the remaining three at the stern numbering some 10 additional torpedoes. With each tube filled and ready to fire (6, four forward and two aft), the total count with the reserves numbered 22 torpedoes.
The deck gun consisted of a single Utof 105mm/45 cannon with 110 available projectiles and was suitable in engaging unarmed or lightly armed surface vessels when possible. The submarine (Type IXC) was defensed by a 37mm anti-aircraft cannon in a single trainable fitting as well as a 20mm anti-aircraft cannon, also in a single trainable fitting. The anti-aircraft gun systems were situated in a stepped fashion along the rear of the sail and, in this setup, offered up an excellent arcs of fire. Of note, however, is that this anti-aircraft arrangement varied on the Type IX boats throughout the course of the war. For example, sometimes the deck gun was given up in favor of an additional Flak system and some single 20mm mounts became quad-mountings instead.
If using the Type IXC as our continued example the vessel was given a top surface speed of 18.2 knots with a submerged speed of 7.5 knots. Her operational range was in the vicinity of 15,535 miles along the surface and roughly 72 miles when submerged. Dimensions included a near-252 feet length, a 22 feet, 2 inch beam and a 15 feet, 5 inch draught. Her displacement was 1,120 tons surfaced and 1,232 tons when submerged. Power on the surface was delivered from twin MAN M9V40/46 supercharged, 9-cylinder diesel engines at 4,400 horsepower. Submerged battery power came from a pair of SSW GU345/34 double-acting electric motors running at 1,000 horsepower. These systems provided propulsion to two propeller shafts held at the stern of the design.