(continued from KTB #111)

The I.J.N. continued to improve L-Type boats, incorporating in them the same modifications that the Royal Navy did in L-Class. Three L-3 type boats were completed in 1922 - 1923, designated as Boat #46, #47 and #57 (later Ro-57, Ro-58 and Ro-59 respectively). These boats carried four 53cm (21 inch) tubes in the bow, and the side-shooting tubes were discontinued. They had a higher freeboard than previous groups, and were more seaworthy.

The artillery armament was moved up to the pedestal on the forward edge of the conning tower, making the gun battle possible in rough seas. The refrigeration system, using carbon dioxide, was set up in the main battery and main motor compartments. The American made hydrophones (K-Tube) were fitted from the start.

L-3 TYPE (Ro-57 Class)

Displacement.............................................................889/1103 tons
Length.........................................................72.72 meters (250 feet)
Beam................................................7.16 meters (23 feet 6 inches)
Draft...............................................................3.96 meters (13 feet)
Machinery............................twin-shaft Vickers diesels of 2,400 bhp, two electric motors of 1,600 ehp
Speed (diesel)..............................................................17.1 knots
Speed (electric)..............................................................9.1 knots
Fuel.....................................................................................75 tons
Radius (diesel)..........................................5,500 miles @ 10 knots
Radius (electric)..............................................80 miles @ 4 knots
Tubes.............................................................four 21 inch fwd only (carried 8 torpedoes)
Guns.........................................................................single 8cm AA, single 6.5mm (.25 cal) machine gun
Depth of dive...................................................60 meters (183 feet)
Crew...........................................................................................46

L-4 TYPE (Ro-60 Class)

Displacement.............................................................988/1301 tons
Length...........................................................76.2 meters (250 feet)
Beam.................................................7.38 meters (24 feet 2 inches)
Draft..................................................3.96 meters (12 feet 4 inches)
Machinery............................twin-shaft Vickers diesels of 1,400 bhp, two electric motors of 1,600 ehp
Speed (diesel)..............................................................15.7 knots
Speed (electric)..............................................................8.6 knots
Fuel....................................................................................102 tons
Radius (diesel)..........................................5,500 miles @ 10 knots
Radius (electric)..............................................80 miles @ 4 knots
Tubes...............................................................six 21 inch fwd only, carried 12 torpedoes)
Guns.....................Ro-60 carried single 12cm/.45 cal low angle gun, Ro-61 & later carried one 80cm/.40 cal low angle gun, single 6.5mm (.25 cal.) machine gun
Depth of dive...................................................60 meters (183 feet)
Crew...........................................................................................48

L-4 type was the last class of boats built under license from Vickers. Nine units were built in 1923 through 1927. Their offensive power was considerable boosted by the six 21 inch torpedo tubes and improved artillery armament. But their displacement increased over the previous class by 20 per cent, and with no improvement in the engine output, their surface speed suffered by a great margin. Those were very well-built boats, and some of them saw action in the Pacific War.

BOAT NR.	Ro DESIGNATION	YEAR BUILT
59	Ro-60	1923
72	Ro-61	1924
73	Ro-62	1924
84	Ro-63	1924
79	Ro-64	1925
- -	Ro-65	1926
- -	Ro-66	1927
- -	Ro-67	1926
- -	Ro-68	1925

The license-built Vickers boats were noted for their sturdiness and the reliability of their engines. It sometimes happened that in the whole Japanese Navy, only Vickers boats were operational while all the other boats were down with mechanical troubles.

More History of the Japanese Submarine Navy

Part 1: 1905
Part 2: 1912-17
Part 3: C-1 and C-2
Part 4: Ha-9, Ha-10 and Tsing-Tao
Part 5: Ro-11, Ro-13, Ro-16
Part 6: Ro-1, Ro-3
Part 7: Kaichu Type 4
Part 8: Batteries
Part 9: Ro-57 and Ro-60
Part 10: I-16
Part 11: O-1 (ex U-125) and O-2 (ex U-46)