|Name||No||Yard No||Builder||Laid down||Launched||Comp||Fate|
|S1 (ex-S1)||Scotts, Greenock, UK||8/1912||28.2.1914||8/1914 // 10.1915||discarded 1.1919|
|S2 (ex-S2)||Scotts, Greenock, UK||10/1913||14.4.1915||5/1915 // 10.1915||discarded 2.1919|
|S3 (ex-S3)||Scotts, Greenock, UK||3/1914||10.6.1915||9/1915 // 10.1915||discarded 5.1919|
|Displacement standard, t|
|Displacement normal, t||
265 / 324
|No of shafts||
2 6-cyl Scott-FIAT diesels / 2 electric motors
|Power, h. p.||
650 / 400
|Max speed, kts||
13 / 8.5
|Endurance, nm(kts)||1600(8.5) /|
2 - 450 TT (bow, 4)
|Diving depth operational, m||30|
In August 1911 a group of Admiralty officers visited FIAT-San Giorgio's works at La Spezia, and were shown the Velilla and Medusa. A month later, Scott's of Greenock, who had been FIAT-San Giorgio's UK licensees since 1909, offered to build a similar boat for £50,000. The tender was accepted that month and S1 was ordered. She was comparable to the 'C' class in size, and had the same armament, 2 450mm TT and 4 torpedoes. Although slightly slower she had a high reserve of buoyancy and a ship-shape form. The main disadvantage was the length of time taken to dive, an inherent problem with the Laurenti type of double-hull construction. Although some sources suggest that the 'S' boats were not sufficiently seaworthy for North Sea operations there is no apparent reason why boats with such a high reserve of buoyancy should be poor seaboats; a more likely reason is the general lack of familiarity with Italian practice and equipment.
The design followed Laurenti's principles, with a partial double hull and a wide 'duck tail' stern. There were no fewer than ten watertight bulkheads, at a time when the 'E' class had only two. Two more boats were ordered in June 1913. All three were transferred to the Italian Navy in 1915 as the RN had more submarines than it could find crews for. They served under the same numbers in Italian service.
No significant events.