St. Laurent-class destroyer

The St. Laurent class destroyer was a class of destroyers that served the Royal Canadian Navy and later the Canadian Forces from the mid-1950s to the mid-1990s.

This was the first major class of warship designed and built in Canada. They were similar to the British Type 12 Whitby class frigate, but used more American equipment than British. There were seven ships of the class commissioned between 1955 and 1957.

They were originally intended as destroyer escorts (DDE) but were later refitted and reclassed as destroyer helicopter escorts (DDH).

Construction
The need for the St. Laurent class came about in 1949 when Canada joined NATO and the Cold War was in its infancy. The RCN was assigned responsibility for anti-submarine warfare and controlling sea space in the western North Atlantic.

Design work for a new class of destroyer escorts began that year with the original completion date slated for 1955. They were designed by Montreal naval architects German and Milne "under the direction of a senior constructor, Sir Rowland Baker, seconded from the [British] Director of Naval Construction... Baker produced a design basically similar to the Whitby [Type 12], but incorporating several ideas of his own....To flatter Canadian susceptibilities, Baker was careful to make the appearance as different as possible from the Whitby, but the ship that resulted was virtually a Type 12 specification (albeit with a different hull form) translated by a different design team."

The St Laurent class were "built to an operational requirement much like that which produced the British Type 12, and powered by the same machinery plant, she was strikingly different. The rounded deck-edge forward was adopted to prevent ice forming." She was designed to operate in harsh Canadian conditions. They were built to counter nuclear, biological and chemical attack conditions, which lead to a design with a rounded hull, a continuous main deck, and the addition of a pre-wetting system to wash away contaminants. The living spaces on the ship were part of a "citadel" which could be sealed off from contamination for the crew safety. The ships were sometimes referred to as "Cadillacs" for their relatively luxurious crew compartments; these were also the first Canadian warships to have a bunk for every crew member since previous warship designs had used hammocks.

Other innovative features not found on other ships of its time included an operations room separate from the bridge, from which the captain could command the ship while in combat, 12 separate internal telephone systems, air conditioning, and the latest advances in radar and sonar technology.

The St. Laurent class originally called for 14 vessels to be commissioned no later than 1955; however, changing design specifications due to the rapidly changing Cold War naval environment, as well as Canada's wartime priorities during the Korean War, saw only the first 7 completed by 1957. The remaining 7 vessels were built as the follow-on Restigouche-class to incorporate advancements in naval warship design in the preceding years. There were also two essentially similar follow-on classes, the Mackenzie Class (4 ships completed 1962-63) and the Annapolis Class (2 ships, completed 1964), the latter completed as helicopter carrying destroyer escorts from the onset, and not converted later as were the seven St Laurent Class ships.

Armament
The St. Laurent class was fitted with twin 3 inch/L50 guns for engaging both surface and air targets. Her anti-submarine armament consisted of a pair of triple barrelled Limbo ASW mortars in a stern well. The stern well had a roller top to close it off from following seas. "As in the case of the Type 12, the design included provision for long-range homing torpedoes (in this case BIDDER [Mk 20E] or the US Mark 35. They were never fitted however."

As built, the twin 3-inch 50-calibre anti-aircraft mounts were installed without shields. These were added in 1963. The gun housings are fibreglass. (Jane's Fighting Ships 1963-64 shows photographs taken in 1962 and 1963 respectively of Skeena and Assiniboine with these.)

Machinery
The vessels of the St. Laurent class had two Babcock & Wilcox water tube boilers installed providing 600 PSI (4.1 MPa, 42 kgf/cm²) at 850 °F.

The steam produced by these boilers was directed at two geared steam turbines which powered two shafts, providing 30,000 HP (22 MW) to drive the ship at a maximum speed of 28.5 knot. By the early 1990s, the quoted maximum speed was only 27 kt.

"Propelling machinery is of British design. Yarrow & Co Ltd, Scotstoun, Glasgow, received an order from Canadian Vickers for the supply of a complete set of machinery for the St. Laurent, the other ships being supplied with machinery manufactured in Canada.  The main turbines and machinery are of English Electric design."

DDH conversion
The advent of nuclear-powered attack submarines in the late 1950s prompted RCN leaders to assess the new threat they posed. Although these craft were noisier than older submarines and could therefore be detected at longer ranges, they were also capable of 30 kn while submerged, which was faster than the top speed of the St. Laurents at 28.5 kn. Some RCN leaders harbored serious doubts that the destroyers could effectively pursue and destroy such fast vessels, even when operating in pairs. During a 25 February 1959 meeting of the Naval Board, it was decided that the Navy would counter the new threat by outfitting destroyers for helicopter operation.

The RCN had examined the feasibility of operating ASW helicopters from small escorts when it modified the Prestonian-class frigate HMCS Buckingham (FFE 314) in mid-1956 with a temporary helicopter landing platform fitted the quarterdeck. Trials held in October 1956 using a Sikorsky HO4S-3 were successful, and a larger temporary helicopter landing platform was installed in the new destroyer escort HMCS Ottawa (DDE 229) in August 1957. Operational trials were conducted using an RCAF Sikorsky S-58, a substantially larger and heavier aircraft than the HO4S, and the success of these tests led to approval of the concept.

To achieve the goal, the RCN needed a helicopter capable of all-weather day-and-night operations with a heavy weapons load- capabilities the HO4S lacked- and a means to handle and secure the aircraft on the landing platform in rough seas. Trials showed landing was not the major concern: deck handling was. Manpower alone was insufficiently quick or certain in all conditions. During the 1957 trials aboard Ottawa, it had taken 30 tense minutes to secure the S-58 to the deck during nighttime operations in rough seas. The deck handling issue was addressed by the invention of the beartrap. The Navy came up with the solution, and contracted Fairey Aviation of Dartmouth, NS, to produce it. Fairey's prototype was installed in HMCS Assiniboine during her 1962-63 conversion. By keeping the aircraft secure, the beartrap eliminated the need for deck handling from landing to the hangar, or from hangar to takeoff.

"In conjunction with the helicopter carrying features and hangar facilities, roll-damping fins were added to the destroyers being so built or converted. These fins reduce the roll of the ship and aid landing and take-off operations during rough weather."

Initial studies identified two helicopters that met the upcoming requirements- the Sikorsky S-61 (HSS-2) Sea King and the Kaman K-20 (HU2K). The Sea King was ultimately chosen in December 1961.

All seven St Laurents were fitted with helicopter platforms and SQS 504 Variable Depth Sonar (VDS). St Laurent was equipped with VDS late in 1961, the helicopter platform to be added later. When ships were fitted with the helicopter platform, the single funnel was altered to twin stepped funnels to permit the forward extension of the helicopter hangar. Stabilizing systems were added to allow for helicopter recovery in any sea conditions, and a single CH-124 was carried. To make room for the helicopter deck, the aft 3 in mount and one of the Limbos were removed.

Assiniboine was the first in the class to receive the full upgrade, re-commissioning as a DDH on 28 June 1963. On 27 November 1963, her new platform was used for the first operational landing of a production CHSS-2 Sea King, and her beartrap landing system was used operationally for the first time a week later.

DELEX program
In the late 1970s, under the Destroyer Life Extension (DELEX) program was commissioned to upgrade ten of the St. Laurent and Restigouche-class ships with new electronics, machinery, and hull upgrades and repairs. The intent of DELEX was to extend the life of these ships for another 15 years of service while the Halifax-class frigates were being designed and built as part of the Canadian Patrol Frigate Program.

DELEX included the installation of a Naval Tactical Data System (NTDS) known as the Automatic Data Link Plotting System (ADLIPS), as well as the Canadian Electronic Warfare System (CANEWS), and a new communication suite.

The DELEX program was very successful as it allowed older ships to participate in a modern electronic battle field using tactical data links between ships and aircraft.

Ships
Note that pennant numbers were originally prefixed DDE but were changed to DDH in the early 1960s.

Significance
In 1997, the Historic Sites and Monuments Board of Canada recognized the St. Laurent Class as being historically significant to Canadians and in 2000 installed a bronze plaque aboard HMCS Fraser which reads: