H21 1918
H28 1939
| Name | No | Yard No | Builder | Laid down | Launched | Comp | Fate |
| H21 | Vickers, Barrow | 3.1917 | 20.10.1917 | 1.1918 | sold 7.1926 | ||
| H22 | Vickers, Barrow | 3.1917 | 14.11.1917 | 11.1918 | sold 2.1929 | ||
| H23 | Vickers, Barrow | 3.1917 | 29.1.1918 | 4.1918 | sold 5.1934 | ||
| H24 | Vickers, Barrow | 3.1917 | 14.11.1917 | 5.1918 | sold 5.1934 | ||
| H25 | Vickers, Barrow | 3.1917 | 27.4.1918 | 7.1918 | sold 2.1929 | ||
| H26 | Vickers, Barrow | 3.1917 | 15.11.1917 | 3.1918 | sold 4.1928 | ||
| H27 | Vickers, Barrow | 3.1917 | 25.9.1918 | 1.1919 | sold 8.1935 | ||
| H28 | 28H, N28 | Vickers, Barrow | 3.1917 | 12.3.1918 | 6.1918 | sold 9.1944 | |
| H29 | Vickers, Barrow | 3.1917 | 8.6.1918 | 9.1918 | foundered in dock 9.8.1926 | ||
| H30 | Vickers, Barrow | 3.1917 | 9.5.1918 | 10.1918 | sold 8.1935 | ||
| H31 | 31H, N31 | Vickers, Barrow | 4.1917 | 16.11.1918 | 2.1919 | sunk 24.12.1941 | |
| H32 | 32H, N32 | Vickers, Barrow | 4.1917 | 19.11.1918 | 5.1919 | sold 10.1944 | |
| H33 | 33H, N33 | Cammell Laird, Birkenhead | 11.1917 | 24.8.1918 | 5.1919 | BU 10.1944 | |
| H34 | 34H, N34 | Cammell Laird, Birkenhead | 11.1917 | 5.11.1918 | 9.1919 | BU 7.1945 | |
| H35 | Cammell Laird, Birkenhead | 1917 | --- | --- | cancelled 10.1917 | ||
| H36 | Cammell Laird, Birkenhead | 1917 | --- | --- | cancelled 10.1917 | ||
| H37 | Cammell Laird, Birkenhead | 1917 | --- | --- | cancelled 10.1917 | ||
| H38 | Cammell Laird, Birkenhead | 1917 | --- | --- | cancelled 10.1917 | ||
| H39 | Cammell Laird, Birkenhead | 1917 | --- | --- | cancelled 10.1917 | ||
| H40 | Armstrong, Elswick | 1917 | --- | --- | cancelled 10.1917 | ||
| H41 | Armstrong, Elswick | 1917 | 26.7.1918 | --- | cancelled 1918 | ||
| H42 | Armstrong, Elswick | 10/1917 | 21.10.1918 | 5/1919 | collision 23.3.1922 | ||
| H43 | 43H, N43 | Armstrong, Elswick | 10.1917 | 3.2.1919 | 11.1919 | BU 11.1944 | |
| H44 | 44H, N44 | Armstrong, Elswick | 10.1917 | 17.2.1919 | 3/1920 | BU 2.1945 | |
| H45 | Armstrong, Elswick | 1917 | --- | --- | cancelled 10.1917 | ||
| H46 | Armstrong, Elswick | 1917 | --- | --- | cancelled 10.1917 | ||
| H47 | Beardmore, Dalmuir | 11.1917 | 19.11.1918 | 2.1919 | collision 9.7.1929 | ||
| H48 | Beardmore, Dalmuir | 11/1917 | 31.3.1919 | 6/1919 | sold 8.1935 | ||
| H49 | 49H, N49 | Beardmore, Dalmuir | 7.1917 | 15.7.1919 | 9.1919 | sunk 27.10.1940 | |
| H50 | 50H, N50 | Beardmore, Dalmuir | 1.1918 | 25.10.1919 | 2.1920 | BU 7.1945 | |
| H51 | Pembroke DYd | 10/1917 | 15.11.1918 | 9/1919 | sold 6.1924 | ||
| H52 | Pembroke DYd | 1.1918 | 31.3.1919 | 12/1919 | sold 11.1927 |
|
Displacement standard, t |
|
|
Displacement normal, t |
423 / 510 |
|
Length, m |
52.4 |
|
Breadth, m |
4.80 |
|
Draught, m |
4.03 |
|
No of shafts |
2 |
|
Machinery |
2 NLSE diesels / 2 electric motors |
|
Power, h. p. |
480 / 620 |
|
Max speed, kts |
11.5 / 10.5 |
|
Fuel, t |
diesel oil 16 |
|
Endurance, nm(kts) |
2975(7.5) / 130(2) |
|
Armament |
4 - 533 TT (bow, 6 - 8) |
|
Complement |
22 |
| Diving depth operational, m | 30 |
Project history: In January 1917 an order was placed with Vickers for 12 boats similar to the 'H' class but with 533mm TT. Engines, main motors and major fittings were obtained from the United States. In June 1917 a second batch was ordered, 6 from Cammell Laird, 8 from Armstrong Whitworth, 4 from Beardmore, 2 from Pembroke DYd and 2 from Devonport DYd, using engines and motors made in England to US designs, but otherwise identical to those in H1-20 and H11-32. The order was cut back when it was decided in October 1917 to build 12 'R' class (using many of the H21 class components). Another was cancelled shortly after the Armistice, so only 22 out of 34 were completed. The main differences between these and the earlier 'H' class resulted from fitting 533mm TT; the hull was 6.4m longer but the diameter of the pressure hull was the same. Displacement went up by 16%. Despite their small reserve of surface stability, inherent in a single-hulled design, they were most successful and some survived to serve in the Second World War, although nominally restricted to training duties.
Modernizations: 1922 - late 1920s, some survived: + type 113 sonar
1942- 1944, survived: + type 286W or type 291W radar
Naval service: Í49 was sunk 18.10.1940 by German trawlers UJ116 and UJ118 off Dutch coast. Í31 was lost for the unknown reason in Bay of Biscay 24.12.1941. H29 foundered 9.8.1926 in dock at Devonport, raised and sold in October 1927. H42 collided with destroyer Versatile 23.3.1922 off Gibraltar and sunk. H47 collided with L12 and sunk 9.7.1929.
H27 1919
© Ivan Gogin, 2008-13