form and two one-tenth-scale launches were built at Sevastopol to test the hull's maneuverability. An old steamship was fitted with a replica of the design's armor decks and tested against bombs, proving that such ordnance would generally penetrate both the upper and middle decks before exploding on the armored deck. The main armor deck was raised one deck in consequence and a splinter deck added underneath it to stop any bomb or shell fragments that might penetrate the armor deck. The underwater protection system was tested on fifteen one-fifth scale models and two full-sized experimental barges. These tests proved that the torpedo belt system of multiple bulkheads was superior to the Pugliese system of a large tube filled with smaller sealed tubes, but it was too late to incorporate these test results into the design as construction was well underway by the time they were completed in late 1939. A revised design was approved on 28 February 1938 and the first ship was to be laid down on 15 July, but even this design was incomplete and would be revised later. Trials with similarly shaped motor launches suggested that the hull's propulsive efficiency would be less than planned, and this was accepted in the November 1938 revision as a maximum speed of . However, a new propeller design proved to be more efficient and was predicted to increase speed to . Another change was the deletion of the centerline rudder when tests showed that the two wing rudders would not be able to counteract its effects if it jammed. The weight toward the stern of the boat was calculated to be too great, producing a substantial stern-down trim. To remedy this, the two 100 mm turrets mounted on the quarterdeck were deleted and the height of the armor belt abreast the rear turret was lowered, but this decision was reversed and they were restored by a decision of the State Defense Committee on 14 January 1941. This forced a revision of the aircraft arrangements as the aircraft catapult had to be removed from the centerline of the quarterdeck; two catapults were added to the sides of the quarterdeck instead. General characteristics As designed, the Project 23-class ships, as Sovetsky Soyuz and her sisters were designated, were long overall. They had a beam of and a draft of at deep load. They displaced at standard load and at full load, although