Here's the latest drawing I've completed (or rather modified from one of my previous drawings), the R class submarine;
Constructed during the late 1920s and early 1930s, the R class were for most of the interwar years the largest SRN submarines in service. They had been designed to be true oceangoing vessels unlike their predecessors the E I and E II types which were little more than coastal craft with their limited range. As resources at the time of their development were spread thin due to numerous other projects being undertaken as a part of the 1928 Fleet Plan, it was decided to modify the basic E II and stretch it to allow for increased fuel and battery space as well as slightly more space for the crew (albeit still very cramped even by submarine standards).
Most of the subs design was common between vessels to minimize the resources needed to produce the new type. The same standard 3 inch deck gun and twin 20mm AA gun were retained along with the standard 4 torpedo tubes forward and single aft with a single reload for each. The R was also equipped to carry two additional torpedoes in the fairing behind the conning tower. This was less than satisfactory in practice however as the collapsible derrick was found to be prone to damage and the torpedoes hard to load into the main hull. Mines could also be stored in the casing.
The early production versions suffered from poor ventilation, fumes posing a hazard in the boats hull even when all hatches were open on the surface. Special valves and ducting had to be designed along the port side of the tower in an effort to force more air through the boat on the surface however the problem was never completely solved. The boats were found to have a poor dive time as well with air frequently being trapped under the deck casing. Later models had a grate decking and increased free flood holes which helped improve the situation somewhat.
Performance overall was less on the surface than their E II predecessors though they did prove to be more steady in a swell. Underwater performance was found to be sluggish but was considered acceptable at the time. Underwater endurance was 4 hours at 7 knots or 19 hours at 2 knots (with the 'creep' motors engaged). On the surface the class averaged 17-18 knots though 21 knots was recorded by R-75 'Ryba' during trials. Range was also vastly improved from their fore bearers with a range of 8,000nm at 17 knots and further at cruise standard speed of 12 knots.
Despite their flaws, the R class were overall considered good boats and served the SRN well through the interwar years and into WW2 even after their more capable replacements had entered service.