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"W" submarines (W1) (4, 1915 - 1916)


Name No Yard No Builder Laid down Launched Comp Fate
W1 I6A   Armstrong, Elswick 10.1913 19.11.1914 1.1915 to Italy 8.1916 (W1)
W2 I7A   Armstrong, Elswick 1.1913 15.2.1915 5.1915 to Italy 8.1916 (W2)
W3 I8A   Armstrong, Elswick 3.1914 28.7.1915 2.1916 to Italy 8.1916 (W3)
W4 I9A   Armstrong, Elswick 3.1914 11.9.1915 6.1916 to Italy 8.1916 (W4)

Technical data

Displacement standard, t 
Displacement normal, t

W1, 2: 331 / 499

W3, 4: 321 / 479

Length, m

W1, 2: 52.4

W3, 4: 45.7

Breadth, m

W1, 2: 4.69

W3, 4: 5.44

Draught, m

W1, 2: 2.71

W3, 4: 2.85

No of shafts



W1, 2: 2 8-cyl Schneider-Laubeuf diesels / 2 electric motors

W3, 4: 2 6-cyl Schneider-Laubeuf diesels / 2 electric motors

Power, h. p.

W1, 2: 710 / 480

W3, 4: 760 / 480

Max speed, kts

13 / 8.5

Fuel, t

diesel oil

Endurance, nm(kts)2500(9) /

W1, 2: 2 - 450 TT (bow, 2), 4 - 450 TC (external drop-collars, 4)

W3, 4: 2 - 450 TT (bow, 4)



Diving depth operational, m30

Project history

The same Admiralty team which visited FIAT-San Giorgio in 1911 also visited the Schneider yard at Toulon to inspect the French Navy's submarine Pluviose and various Schneider-Laubeuf designs. They concluded that the French boats were too long and too slow, and in particular they did not like the Drzwiecki drop-collars carried outside the casing. In spite of this adverse report two were ordered from Armstrong Whitworth, for no better reason than keeping a promise to the firm to order two submarines per year (however, there was great enthusiasm for foreign double-hulled designs in the Submarine Service). Two were therefore ordered under the 1912-13 Estimates, and keels of W1 and W2 were laid in October and December 1913 (order placed January 1913). Seven months later W3 and W4 were ordered from the same builders, but considerably modified by M Laubeuf to meet RN requirements.

In spite of delays in redrawing and redesign the first pair were built remarkably quickly, 15 and 17 months respectively. The principal difference between the two groups was the omission of the drop-collars in W3 and W4. The engines were Schneider-Laubeuf diesels, but 8-cyl type in the first two and 6-cyl in the later pair. The chief complaint in service was poor habitability, caused mainly by the small diameter of the pressure hull, but somewhat mitigated by the lack of internal framing. In their defence, however, the DNC commented that that they had unusually good control when diving, while the detailed design of flooding, venting and other subsidiary installations was practical and efficient.



Naval service

As the RN had a surplus of submarines and because these four boats, like the 'S' class, were non-standard, they were handed over to the Italian Navy in 1916, retaining their original numbers.