J Class (1915) SS

The J Class (1915) were another attempt to obtain a submarine able to work with the main Fleet, while using diesel-electric power. They were also to replace the successful E Class (1913) overseas boats.

For Fleet use they needed to have a speed of at least 21kts. Which was a significant increase on the 15kts which was the norm for submarines of the time. To achieve this they had an additional third diesel engine added in a 50% longer hull, while adding a second shaft.

The result was a  4kts faster, larger, heavier hull, too slow for Fleet use.

So, with the larger K Class (1917), steam powered boats in prospect for Fleet use, the J's were reclassified as long range overseas submarines. Despite this they were based at Blyth and tasked with the Grand Fleet. So they saw little action in WW1.

A total of eight boats were ordered in Jan-1915, but two had been cancelled by April. The remaining six were then renumbered. 

In May-1915 another boat J7, was ordered to modified internal design. Having the Control room positioned between the two engine rooms. This gave better access space for bow torpedo tubes and slightly lower weight. But it gave no increase in performance. 

Six boats of the seven boats survived WW1.

With the end of WW1 the Royal Navy wanted to dispose of surplus boats as soon as possible. But the J's long range made them useful in the Pacific. So they were refurbished and transferred to the Royal Australian Navy. 


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This page last edited - 12 December, 2012.

Copyright Ian M King, except where otherwise indicated.