By William Pearce
In the early 1930s, Rudolf Engelmann of Berlin, Germany began investigating designs to improve the hull shape of seagoing ships. Engelmann felt that a new hull shape could be devised that would significantly improve how efficiently a sea-going ship plowed through the water. At the time, the fastest ocean liners and destroyers were capable of around 35 mph (56 km/h) and 46 mph (74 km/h) respectively. Engelmann’s goals were to increase speed to 46–58 mph (74–93 km/h) with the same amount of power and enable ships to maintain higher speeds through rough seas.
Engelmann used models to test various hull shapes. On 25 March 1934, Engelmann applied for a German patent (no. 651,390) that outlined his design. Engelmann’s ship had a shape that was very similar to a modern-day submarine—a cigar-shaped (fusiform or spindle-shaped) hull with a propeller at its end and a superstructure in the middle. However, Engelmann’s ship was not fully submersible. The hull traveled beneath the water’s surface, but the superstructure sat above the waterline. The hull’s cross section was pear-shaped, with the narrow part in the middle positioned at the waterline. The submerged hull increased the ship’s efficiency and improved the ship’s stability in rough seas. The superstructure had a streamlined form to cut through the water and slice through waves.
After the first patent, Engelmann continued to develop the semi-submersible design. He applied for two other patents in 1935 that detailed an updated hull shape. The difference between the two later patents was detailed in German patent 651,893, which included a chine added to the superstructure. Tests indicated that in rough seas, the superstructure of the previous designs had a tendency to build up a bow wave. In addition, the design’s minimal reserve buoyancy caused the ship to plow under waves. To correct these issues, the thickness of the leading edge of the superstructure was reduced, and chines were added above the waterline. The chines tapered back and were blended into the sides of the superstructure. They directed water down from the superstructure rather than over it. The additional area created by the chines increased the ship’s displacement and buoyancy with the wave action.
Engelmann’s experiments caught the attention of the Kriegsmarine (German Navy), which felt the hull design had military applications. Having the superstructure as the only part of the ship above the water decreased the ship’s detection range and also presented a small target for an enemy to hit. Combined with its high speed, a ship of Engelmann’s design could get very close to an enemy ship undetected, launch torpedoes, and then quickly retreat to a safe distance. Around 1938, the Kriegsmarine ordered a proof-of-concept prototype be built.
The prototype was designated Versuchs Schnellboot 5 (Experimental Fast Boat 5 or VS 5) and was also referred to as the Engelmann-Boot. The ship was a semi-submersible, fast-attack torpedo boat for use in coastal waters. The VS 5 was built along the lines specified in Engelmann’s third patent. Rudders and stern planes at the rear of the ship provided control. The VS 5’s armament consisted of two forward-firing, 21 in (533 mm) torpedo tubes in the bow of the hull and two 20 mm cannons atop the superstructure. However, it is not clear if the weapons were ever installed in the prototype.
Power was provided by four MAN (Maschinenfabrik Augsburg-Nürnberg) L11Z 19/30 diesel engines. The L11Z 19/30 was an 11-cylinder, double-acting, two-stroke, inline engine capable of reverse operation. Each of its closed cylinders had a combustion chamber at the top and bottom of the cylinder. A single intake manifold brought air into the cylinders, where the air was directed either above or below the double-sided piston, depending on its stroke. Separate exhaust manifolds collected exhaust gasses from the upper and lower combustion chambers. The engine had a 7.48 in (190 mm) bore and a 11.81 in (300 mm) stroke. Since the piston was double-acting and there was an upper and lower combustion chamber, the engine’s displacement was nearly doubled, as if it had 22 cylinders. However, the connecting rod passing through the lower combustion chamber took up around 40 cu in (.66 L) of volume. Total displacement for the upper combustion chambers was 5,710 cu in (93.56 L). Total displacement for the lower combustion chambers was approximately 5,269 cu in (86.35 L). The L11Z 19/30’s total displacement was around 10,979 cu in (179.91 L). The engine had a maximum output of 2,000 hp (1,491 kW) at 1,050 rpm and a continuous output of 1,400 hp (1,044 kW) at 900 rpm. The four L11Z 19/30 engines were installed in two rows in the middle of the VS 5 and were connected to a common gearbox that drove a single propeller.
The VS 5 was 160 ft 3 in (48.84 m) long and 9 ft 3 in (2.82 m) wide. The keel sat about 11 ft 10 in (3.6 m) under the waterline. The superstructure was around 66 ft (20 m) long and rose about 12 ft 6 in (3.8 m) out of the water. The VS 5 displaced some 292 tons (265 tonnes) and had a forecasted top speed of 58 mph (93 km/h). The ship had a full crew of 17. Some sources state the VS 5 could sink in shallow water to hide from enemy ships. Once submerged, it could not move (other than surfacing), as the ship did not have batteries or the capability to run its engines while underwater. However, the ability to intentionally sink is not mentioned by all sources.
Construction of the VS 5 started on 1 April 1940, and the ship was built by Deutsche Schiff- und Maschinenbau Aktiengesellschaft (Deschimag) in Bremen, Germany. Deschimag was a conglomerate of eight German shipyards. The VS 5 was launched on 14 January 1941, and trouble was encountered soon after testing began. Despite the changes in Engelmann’s design, the VS 5 still had a tendency to plow under waves in heavy seas. In addition, torque from the single propeller caused the whole ship to list around 14 degrees as full power was applied. The issue was so severe that a speed of 32 mph (52 km/h) could not be exceeded because of the tilt.
The VS 5 project was apparently abandoned in 1942, and what happened to the ship is not known. Plans for a larger 661-ton (600-tonne) ship were cancelled. Twin propellers were planned for the larger ship, and their configuration would have cured the list issues caused by the single-propeller. Engelmann’s design concept was passed over as the Kriegsmarine focused on submarines and fast boats, rather than a combination of the two.
“Schiff” German patent 651,390 by Rudolf Engelmann (granted 23 September 1937)
“Schiff” German patent 651,892 by Rudolf Engelmann (granted 30 September 1937)
“Schiff” German patent 651,893 by Rudolf Engelmann (granted 30 September 1937)
“Improvements relating to the construction of Ships” GB patent 455,466 by Rudolf Engelmann (granted 21 October 1936)
“Improvements relating to the Construction of Ships” GB patent 470,907 by Rudolf Engelmann (granted 20 August 1937)
“High Speed Seagoing Ship” US patent 2,101,613 by Rudolf Engelmann (granted 7 December 1937)