Rothesay class frigate

The "Rothesay" class, or Type 12M frigates were a class of frigates serving with the Royal Navy, South African Navy (where they were called President class frigates) and the New Zealand Navy.

The original Type 12 frigates, the "Whitby" class, were designed as first rate ocean-going convoy escorts in light of experience gained during World War II. However, such were the capabilities and potential of the design that it was deemed suitable for use as a fast fleet anti-submarine warfare (A/S) escort. As such, a repeat and improved Type 12 design was prepared, known as the Type 12M (Modified), named after the lead ship HMS "Rothesay". A total of twelve vessels were constructed, with the lead ship being laid down in 1956, two years after the last "Whitby". The design was successful and popular, serving the Royal Navy and South African Navy well into the 1980s and serving with distinction in the Falklands war.

Design

The Type 12M retained the excellent hull design of the Type 12, that allowed high cruising speed to be maintained in heavy seas, critical to the success of A/S warfare in the era of the threat of the high-speed Soviet submarine. Armament and the propulsion plant remained largely unchanged. The main external differences were an enlarged raked and streamlined funnel (retrospectively fitted to the "Whitbys") and a modified after deckhouse, enlarged to carry the Sea Cat anti-aircraft missile launcher and its associated GWS-20 director and handling rooms as it became available. This weapon was not available originally, therefore a single 40 mm Bofors Mark 7 gun was shipped in lieu. The arrangement of the torpedo tubes was also altered in the new design, with 4 fixed tubes firing aft at 45° on each beam, in front of a trainable twin mounting; the reverse of the arrangement on the "Whitbys". A suitable weapon was never developed for these tubes, so they remained unused, or were never fitted. Internally, electrical generation capacity was increased to handle the increasing demands created by improved ships electronics. Accommodation standards were also improved, with partial bunking and air conditioning.Such was the success of the "Rothesay" design that it was elaborated into the excellent general purpose "Leander" class frigate, the Type 12I.

Modification

Increasing submarine performance in the 1960s demanded detection and engagement of targets at a greater distance from the fleet. Detection was improved with new sonar designs such as the Type 177 search and Type 199 Variable depth. To attack targets at a greater range, the Royal Navy adopted the "MATCH" (MAnned Torpedo Carrying Helicopter) system. MATCH was essentially the Westland Wasp HAS.1, a lightweight navalised helicopter small enough to operate from a small hangar and flight deck that could be fitted to contemporary frigate designs yet large enough to carry a pair of A/S homing torpedoes (US Mark 44 or 46 types), allowing engagement of underwater targets at some distance from the parent vessel, outside the range of the shipboard Limbo A/S mortars. To allow MATCH to be carried, all of the Type 12I class were modified and modernised, beginning with "Rothesay" from 1966 and finishing in 1972.

The after superstructure was removed, along with the foremost Limbo mortar, with the well being plated over to create a small flight deck. A small hangar was constructed in front of this, on top of which the GWS-20 Sea Cat missile and director was (finally) shipped. The mainmast was replaced by am enclosed design, carrying the Type 1010 IFF antennas, with the funnel height was increased to carry the hot exhaust gasses over the taller superstructure. The electronics fit was also upgraded from the World War II era sets fitted in the "Whitbys". A large, enclosed foremast replaced the short lattice, carrying the distinctive "half cheese" antennas associated with the Type 993 target indicator. The Mark 6M director was replaced with the MRS3 system carrying radar Type 903, allowing the removal of the Type 277Q height finder. Additionally, Knebworth/Corvus 3in countermeasures launchers were fitted on either side of the bridge, as were a pair of World War II vintage 20 mm Oerlikon guns for "policing" work (and strictly limited anti-aircraft defence).

The extensive modifications of the "Rothesays" brought their fighting capabilities into line with the that of the original "Leander" class vessels.

ervice

The "Rothesays" served throughout the 1960s and 1970s, with "Londonderry" converted into a weapons and electronics trials vessel in 1975. At the beginning of 1982 many of the class had been relegated to the Standby Squadron, likely to be disposed of following the 1981 defence review, with their sister ships likely to follow suit. However, the outbreak of the Falklands War reprieved the class, and "Plymouth" and "Yarmouth" were despatched with the task force, with "Plymouth" in particular playing one of the most active roles of any ship. In addition the rest of the class were refitted for service, allowing the losses and damages suffered by the Royal Navy during the conflict to be rapidly made good. The class paid off throughout the 1980s, with "Rothesay" finally paying off in 1988. The demise of the class also saw the withdrawal of the Wasp helicopter, the "Leanders" having been upgraded to carry the Westland Lynx.

Vessels

ee also

*River class destroyer escort - Australian ships based on the Type 12.
*"Whitby" class frigate - the original Type 12 design.
*"Leander" class frigate - the Type 12M frigate, a general purpose design following on from the success of the Type 12I

References

Further reading

*"Royal Navy Frigates 1945-1983" Leo Marriot, Ian Allan, 1983 ISBN 0-7110-1322-5