A newly designed fast patrol boat (FPB), intended for employment in those areas where heavier armament, greater endurance, and seakeeping qualities outweigh the tactical advantages of high speed has been introduced by the Vosper-Thornycroft Shipyard. It is their third private venture. The first prototype, completed in 1937, was incorporated into the Royal Navy as the MTB.102. The second, the Ferocity, was completed in 1960 and used as a demonstration and trials craft until she was scrapped in 1968.
The existing Vosper Thornycroft FPBs have reached a high level of development and fall into two main groups: the 96-foot, hard-chine, gas turbinecraft of wood construction and capable of 55 knots; and the 102-110-foot round-bilge diesel craft of steel construction and capable of 23-30 knots depending on the power plant selected. Three of the 96-foot craft were built for the Libyan Navy.
The new boat is 142 feet long, has a 25-foot beam, and displaces 220 tons; she was designed for duties where much heavier long-range armament, coupled with the improved seaworthiness and greater endurance, outweighed the tactical advantage of high speed of the earlier fast patrol boats.
Recent developments in weapons and their control equipment dictated an increase in size. Despite their compactness, they could not be properly integrated in the weapons payload available in a 100-foot, 100-ton FPB. Guns and missiles—such as the 76-mm. OTO-Melara or twin 35-mm. Oerlikon and the Contraves Sea Killer—are light enough to be installed in FPBs, and both can be linked to the Contraves Sea Hunter 4 fire control system. They are more accurate and effective than the weapons now carried in FPBs, and enable them to engage major surface units and aircraft on an equal basis.
The hull of this new FPB is of all-welded mild steel construction and round bilge form, with a spray-deflecting knuckle extended well aft, while aluminum alloy is used for the superstructure. The increased dimensions, together with active fin stabilization, result in improved seaworthiness compared with the 100-foot craft, and enable the new FPB to remain at sea for a one-week period, under all weather conditions.
A choice of two propulsion systems is available, both giving a maximum speed of about 40 knots. The longer casing required by the combination diesel or gas turbines (CODOG), encroached on deck space aft so that fixed ramps are provided for the Sea Killer missiles, while a trainable launch ramp is fitted to the diesel engine version. The choice of power plant is dictated by maintenance, training, and logistics facilities.
With the CODOG version main propulsion is by three Rolls-Royce Proteus gas turbines, each developing 4,250 h.p. and driving its own shaft through V-drive reduction gearing. Coupled to each wing shaft is a diesel engine, either a six-cylinder, 700 b.h.p. Paxman Ventura-type giving 1,500 r.p.m., or a 750-b.h.p. Maybach Mercedes-Benz, giving 1,500 r.p.m. for a cruising speed of 15 knots, and a range of 2,500 miles. Electric power at 450 volts a.c. is supplied by two or three 100-kilovolt-ampere alternators, powered by Rover gas turbines.
The diesel engine version has four shafts, each driven by either an 18-cylinder English Electric Deltic type unit, with a maximum rating of 3,100 b.h.p. at 2,100 r.p.m.; a 20-cylinder Maybach Mercedes-Benz unit, with a maximum rating of 3,500 b.h.p. at 1,700 r.p.m.; or a 16-cylinder Maybach Mercedes-Benz unit, with a maximum rating of 3,600 b.h.p. at 1,900 r.p.m. They are all turbocharged and uni-directional engines driving through reverse/reduction gearboxes. Electric power at 450 volts a.c. is supplied by three 96 kilovolt-ampere alternators, which are powered by Foden diesel engines.
The hull arrangement differs with both engine types. The engine rooms are aft in the CODOG version to provide short exhausts for the gas turbines which discharge through the transom stern. The engine rooms are placed amidships in the diesel version. All controls for the main and auxiliary machinery, together with the main switchboard, are contained in the machinery control room, which is linked to the wheelhouse by engine order and revolution telegraphs. Full alarm and protection equipment and complete instrumentation are provided so that all running machinery can be supervised by a single watchkeeper.
There are berthing spaces for the commanding officer, two or three officers, four to six petty officers, and 20 to 24 enlisted men. The larger complement is required for the diesel version. All living and working spaces except for the engine rooms, are air conditioned. The accommodation spaces are thermally insulated at the sides and underside of the upper deck, and acoustically insulated on the engine room bulkheads. While steel bulkheads are used to subdivide the hull into eight watertight compartments, internal partitioning is a rigid, expanded plastic foam, which is faced with plastic laminate.
The operations room is located at the forward end of the superstructure, and is backed by an enclosed wheelhouse and open upper bridge, both partially raised to provide clear ahead vision. Fire control consoles and their associated equipment, a gyro compass, AGT electric-magnetic log, echo sounder, and a navigational radar are all contained in the operations room. Communications equipment includes marine, air, and shore bands, IFF and ECM equipment, and the internal action information and armament broadcast systems, with the necessary emergency equipment, telephones, and voicepipes.
Wheelhouse equipment includes helm and engine controls, and autopilot. For target illumination, there are 2-inch rocket flare projectors located on each side of the bridge.
The Sea Killer is a beam-riding surface-to-surface missile with a range of 20-km. and a low flight altitude. While the radio altimeter is contained in the missile, it can be controlled from the ship to adjust height. Visual bearing guidance, by a “joystick” control is provided as an alternative when radar jamming is employed. The missile has a total weight of 375 pounds, a length of nearly 15 feet, an 8-inch diameter, and a wing span of almost three feet. The 110-pound warhead is fitted with contact and proximity fuses. The missile is powered by solid-propellant booster and sustainer motors.
The 76-mm. and 35-mm. guns are fully automatic in power-operated mountings. The choice between them must rest on the preferred requirement for weight or rapidity of fire. They are both compatible with the Sea Hunter 4 fire control system, which can control both guns and missiles, either separately or together, by day or night.
The Contraves Sea Hunter 4 fire control is a proven system, having been installed in nearly 100 warships. It is compact, lightweight, and of simple design, enabling it to be fitted in FPBs. A limited number of modules permits easy maintenance and fault diagnosis, while rapid-system performance checking is possible with built-in test equipment. The fullest use is made of transistors and minaturized [sic] electronic components to secure a high reliability and reduced power consumption, and heat dissipation eliminates special cooling measures.
Enhanced visual search and aiming capability at night is provided by a television camera mounted on the stabilized antenna. Targets are acquired by its integrated search radar or visually from optical sights. The fire control antenna can be manually operated to search for targets, or by an automatic adjustable helical search program. Once a target has been acquired, prediction and aiming of the linked weapons are automatic, leaving only the firing controls to be operated. When radar range is not available target settings can be applied manually to the Sea Hunter system together with spotting corrections for surface action or shore bombardment. A track-while-scan circuit enables one or more surface targets to be tracked using the search radar, while a separate target is simultaneously tracked by the fire control radar. Consequently, when shifting target, the new target can be rapidly acquired and brought under radar-controlled fire.
The private venture by Vosper Thornycroft is strictly experimental. From past experience, however, there is much reason to believe that the missile-armed fast patrol boat is a requited weapon for any navy.