A distinctive feature of the Soviet boats was their small size, and consequently, they had a small displacement and weak armor. But at the same time, they were able to develop high speed and good maneuverability. Basically this series of boats were the G-5 and Komsomolets. Based on these features, their methods of attack were developed. Observers could conclude that the Soviet boat actions could seem like madness at times, but they acted on the basis of the characteristics of their boats and on a correct assessment of enemy action. A group of engineers of the Leningrad Shipyard took into account the weaknesses of the G-5 and created a totally different boat with a duralumin hull. The boat was called Komsomolets. The new boat had a hollow beam that went lengthwise and took on the role of the keel. There were also some bilge keels below the water line; these keels reduced the rolling. Komsomolets had the same measurements as the G-5 but the navigability of the former was increased to 4 points. The new boat was armed with two bow torpedo launchers for 21'' torpedoes, one DShK machine-gun and four depth-charges. The first Komsomolets was laid down in July of 1939; it floated in May of 1940. Its speed was 52 kts at official tests in Sevastopol. The boat was improved in 1942 by engineers of TsKB-32 (Central Design Office 32). One DShK machine-gun was replaced with four coupled DShKM machine-guns, the torpedo launchers were replaced with torpedo tubes, the cabin and the machine-guns were protected by 7 mm armour. The caliber of the torpedoes had to be lowered to 18'' in order to avoid overloading. Boats of this type were equipped with Packard engines. As a result of all of these changes, the tonnage of the boat had increased by 5 tons and the speed had decreased by 4 knots. The main weakness of these boats was their small cruising range - only 240 miles at a speed of 13.5 kts. Four of these boats floated in the Baltic Sea and 26 of them in the Far East in 1944-45.