Grampus 1939
| Name | No | Yard No | Builder | Laid down | Launched | Comp | Fate |
| Grampus | M56 - N56 | Chatham DYd | 8.1934 | 25.2.1936 | 3/1937 | sunk 16.6.1940 | |
| Narwhal | M45 - N45 | Vickers-Armstrong, Barrow | 5.1934 | 29.8.1935 | 2/1936 | sunk 30.7.1940 | |
| Rorqual | M74 - N74 | Vickers-Armstrong, Barrow | 5/1935 | 21.7.1936 | 2/1937 | BU 3.1946 | |
| Cachalot | M83 - N83 | Scotts, Greenock | 5.1936 | 2.12.1937 | 8/1938 | sunk 30.7.1941 | |
| Seal | M37 | Chatham DYd | 12.1936 | 27.9.1938 | 5/1939 | captured by Germany 30.5.1940 (UB) | |
| P411 | Scotts, Greenock | 1941 | --- | --- | cancelled 9.1941 | ||
| P412 | Scotts, Greenock | 1941 | --- | --- | cancelled 9.1941 | ||
| P413 | Scotts, Greenock | 1941 | --- | --- | cancelled 9.1941 |
|
Displacement standard, t |
1520 |
|
Displacement normal, t |
1810 / 2157 |
|
Length, m |
89.3 |
|
Breadth, m |
7.77 |
|
Draught, m |
5.13 |
|
No of shafts |
2 |
|
Machinery |
2 Admiralty diesels / 2 electric motors |
|
Power, h. p. |
3300 / 1630 |
|
Max speed, kn |
15.75 / 8.75 |
|
Fuel, t |
diesel oil 119 - 147 |
|
Endurance, nm(kts) |
5880(9.3) / 64(4) |
|
Armament |
1 x 1 - 102/40 QF Mk XII, 6 - 533 TT (bow; 12), 50 M3 mines |
| Sensors | type 129 sonar |
|
Complement |
59 |
| Diving depth operational, m | 60 |
Project history: Unique British purpose-built minelaying submarines. Porpoise was built under the 1930 Programme. Design was created on basis of "Ð" class. Saddle-tank submarine had an operational diving depth 60m, maximal depth 95m. Fuel tanks were arranged out of a pressure hull and were welded. Two horizontal mine tubes placed in a superstructure and extended from an aft end in a bow on about 70m.
After a lead boat 5 more were followed (1932-1935 Programmes), built on modified design. They had double-hulled construction similar accepted on Thames class fleet submarines. Hull lines were streamlined to raise speed a little at same engine power. Fuel tanks have placed in a pressure hull, the truth, for it was necessary to pay by reduction of fuel stowage.
Already after a beginning of war, under the "War emergency" Programme it was decided to built 3 more submarines of this class and in January, 1941 even the order has been given out. Soon, however, they were cancelled, as necessity in specialised minelayer has disappeared after appearance of the special mines laid from TTs.
Modernizations: 1940s, Rorqual: can carry 12 M2 mines in TT instead of torpedoes
1942 - 1943, Rorqual: + 1 x 1 - 20/70 Oerlikon Mk II/IV, type 286W or type 291W radar
1/1946, Rorqual: 1 x 1 - 102/40 S Mk I, 1 x 1 - 20/70 Mk IIA S/M, 6 - 533 TT, 50 mines, type 286W or type 291W radar, type 129 sonar
Naval service: One submarine, Seal, became the unique British ship which has surrendered to the enemy (4.5.1940 was mined in Skagerrak, badly damaged and surrendered to German patrol ships; subsequently she served in German Navy as UB; she was scuttled 3.5.1945). Grampus was sunk by DCs of Italian torpedo boats Circe and Clio off coast of Sicily 16.6.1940. Narwhal was sunk by German aircraft off coast of Norway 30.7.1940. Cachalot was sunk by ramming of Italian torpedo boat Generale Achille Papa at Bengasi 30.7.1941.
© Ivan Gogin, 2008-10