The First in a Series of Four Oceangoing Patrol Vessels for Royal Netherlands Navy

In 2005, a study by the Dutch Navy concluded that changes in the field required a different type of vessel. The study proposed selling four frigates of the Karel Doorman class, measuring 122 metres for a crew of 154, and replacing them with four new Oceangoing Patrol Vessels, with a permanent crew of 50 and accommodation space for 40 non-listed crew. Since the end of the cold war, the focus has increasingly shifted from traditional combatant warfare to facing more unconventional threats: pirates, smugglers and terrorists rather than large foreign navies. It is due to the demands of this so-called asymmetric warfare, but also with humanitarian missions in mind, that the Holland class of ships was conceived, resulting in longer endurance, all-weather operability, self-sustainability, versatility, smaller crews and more economic operation at patrol speeds.

All-weather operability

The requirement to operate safely in a sea state 5 (waves up to four meters, winds up to 21 knots) resulted in a minimum length of 90 metres. The heli-deck demanded a beam of at least 14 metres for safe landing and launching. The speed of the ship is also crucial. Instead of putting in a massive amount of horsepower to push the 3,750 ton ship up against the resistance curve for an increase from 20 to 30 knots, the Royal Netherlands Navy chose to go about it in a smarter way. While the ship’s top speed remains in the displacement regime at 22 knots, it can quickly launch a NH-90 helicopter and two FRISCs, short for Fast Raiding Interception & Special Forces Craft. The twelve metre long FRISCs are rigid inflatable boats with an inboard diesel engine. They can achieve a top speed of 45 knots and have a range of 172 nautical miles. The helicopter and the FRISCs have onboard fire-power and operate as the Holland’s tentacles. Through their communication system, they benefit from the advanced sensor package onboard the mother ship.

Launching at speed

While one of the FRISCs is davit-launched from the side, requiring slow sailing (one to five knots), the other is stored on a slipway recessed in the stern, enabling launching at speeds up to twelve knots. At speeds above twelve knots, the depression in the slipstream of the ship becomes too deep and the stern wave too high for safe launching. In the stern, a non- watertight hatch can be rolled inboard just like a segmented garage door. To retrieve the FRISC from the water, it first needs to sail as far onto the ramp as possible. For the last bit, the boat is caught by a hook to a triangle and can be pulled inboard with electric winches. The triangle can also be pulled in the outboard direction to assist in the launching of the boat.

“Together with the helicopter, the FRISCs can be used as hunting dogs, granting a view over the horizon, bringing boarding teams to other vessels or carrying out interventions”, describes project manager Rob Zuiddam from the Defence Material Organisation (DMO). To enable the launching of the FRISCs and the helicopter in rough seas, the Holland is equipped with a pair of Quantum fin stabilizers. These fins feature a low aspect ratio and an unbalanced shaft position to make them effective at low speeds,  much like zero-speed fin stabilizers on large motoryachts.

Helicopter

The helicopter can be hauled into the hangar, blades folded, by carts which clamp onto its front wheel and a strong point attached to the airframe. The cart is pulled by cables which run inside two recesses in the deck. The system was devised by Bosch Rexroth. The heliplatform is equipped with a landing grid, into which the pilot can lower a harpoon to create a secure connection to the deck in an instant. When departing, the pilot can release the harpoon at the most convenient moment and take off right away. A refuelling installation is provided, not only for a landed helicopter, but even for in- flight refuelling of larger helicopters. The safety net frames around the aft deck can be lowered and raised hydraulically at the flick of a switch.

Propulsion

Typically for a patrol vessel, the Holland class of ships will spend a large portion of their time trolling at five knots. For the 2 x 5.400 kW main engines, type 12V28/33 from MAN Diesel, such endured low loading (below 20% of MCR) would be very disadvantageous (causing unnecessary fouling of the exhaust gas system). That is why the engineers at DMO and Damen Schelde Naval Shipbuilding have specified dual input- single output gearboxes. At speeds up to nine knots, the ship can sail in pure electric mode, powered by two 400 kW e-motors mounted on PTIs (Power Take In) on the gearboxes. Above 14 knots, both main engines are engaged for a classic diesel-driven propulsion. Tests during the sea trials have shown that at speeds between nine and 14 knots, the most efficient operation, coupled with sufficient engine loading, is the single shaft propulsion mode. This is achieved by setting one of the propellers at its maximum pitch, and letting it freewheel, while the other propeller is powered by its diesel engine. The five-bladed controllable pitch propellers were supplied by Rolls Royce, one of only two suppliers worldwide which can supply five- bladed CPP propellers.

The main engines and generators are cooled with seawater, from a cross-over made of cunifer piping. All the exhausts pass through a damper for noise reduction. Project manager Jeroen Waalewijn from Schelde Naval Shipbuilding says: “With her 500 cubic metres of fuel, the Holland has a range of over 5,000 nautical miles at a speed of 16 knots. There is also a refuelling installation, to allow bunkering at sea from a supply ship as HNLMS Amsterdam.” Two generators of 968 kW are installed in the aft engine room and one 968 kW genset is positioned between the main engines in the forward engine room. Two of the gensets are sufficient to cover both the ship’s electrical consumers and either the electrical propulsion or the electrical bowthruster (rated at 540 kW). It is not possible to use the bowthruster in conjunction with the electrical propulsion.

Seakeeping

An important aspect in the design of the Holland class was the seakeeping behaviour. Extensive model testing in the towing tank resulted in a moderately flaired bow and a relatively far aft position for the wheelhouse to avoid slowing down due to green water over the bow or excessive motions on the bridge. Commander Chris van den Berg reports excellent characteristics at sea: “Even in a wind force 10, we could sustain a speed of 15 knots, without shipping green water over the foredeck. The bow slices neatly through the waves, without causing excessive pitching.” The hull form is a classic round-bilge shape, with a small immersed stern area. Bilge keels, in conjunction with the fin stabilizers, minimise the rolling motions, while a skeg and a pair of spade rudders ensure directional stability.

The ship’s colour was based on a test programme carried out by the Dutch research organization TNO. It is a light greyish blue, resulting in minimal visibility from a distance of about six miles. When the weather is just slightly foggy, the ship almost disappears entirely. No special measures were taken to minimise the visibility on radar. The Holland was built with regular steel, but the watertight bulkheads were constructed as so-called ‘blast bulkheads’. They can sustain more deformation and absorb more energy than regular bulkheads, increasing the chances of containing damages within one compartment. An impressed current corrosion protection system is used to protect the hull from corrosion.

Fewer hands on deck

A lot of measures have been taken to minimise the crew needed on board. Two elevators are installed, one of which leads directly from the aft deck to the provisioning stores and the multi-functional space below. The forward elevator connects the non-food stores with the accommodation decks in the forward part of the ship. Most importantly, a very high level of automation means that less crew is needed ‘on watch’. In addition to the requirements of the unmanned machinery space notation, each crew member has a handheld PDA (a ruggedized smartphone), through which he or she receives all relevant alarms and which can be used for internal communications. A wireless network is installed throughout the ship for VOIP telephone communications and to support the PDA system.

The crewlist is also shortened by diversifying their tasks. Although only five deck ratings are on board, officers on watch are expected to help with line handling during manoeuvring operations. The logistical services department has also been reduced. There is no baker, as pre- baked bread is used, and no dedicated laundry person. All people on board eat in the same mess and are served in buffet style. The crew onboard will be supported by a shore-support team of 20 for the four Holland class OPVs. The team is based in Den Helder and takes care of maintenance and administrative and logistic tasks. Team members can be sent to one of the ships for specific tasks or as substitutes for onboard crew members in the case of illness.

Self-sustainability and versatility

An important aspect of the Oceangoing Patrol Vessel’s task is humanitarian relief. Under the aft deck, a multi-purpose space is located, which can be used to ship relief goods or may be equipped with beds for up to 96 evacuees. Particularly practical is a large deck hatch, which allows a container to be placed directly into the space. A big help in this respect – and a novelty on Oceangoing Patrol Vessels – is the large deck crane, which has a safe working load of ten tons at twelve metres. Furthermore, the Holland has a small hospital facility with a treatment room and a ward with two beds. Although a doctor is not normally on board, the nurse can use the broadband satellite link to establish communication with specialists on shore.

Safety for the crew onboard is ensured for example in the form of a watermist fire extinguishing throughout the ship, including the engine rooms, and with a marine evacuation system (M.E.S.) for 100 persons on port and starboard. The M.E.S. consists of a liferaft and inflatable slide, which can be launched through a hull door. To protect the onboard climate in case of operations in toxic air, due to calamities or attacks, all openings to the exterior can be closed to form a ‘gas citadel’.

Green credentials

One of the starting points for the new design was that it should minimise the impact on the environment. The Holland class OPVs feature a low fuel consumption, courtesy of their diesel- electric trolling capability. In the summer of 2011, half of the time sailing was spent with the main diesel engines shut down. The ships also have a new type of sewage treatment plant, with bio-reactor to guarantee a perfectly clean effluent. A ballast water treatment system will also be installed.

E-installation

The complete electrical installation was entrusted to Alewijnse Retec Romania, including the engineering, delivery, installation and commissioning of the lighting installation, main, emergency and auxiliary switchboards and panels and motor control centres. It was the company’s first contract with a naval client, requiring a high level of robustness, quality and documentation. The procedures for installing and testing of the fiber optic, CAT6e and coax cables were approved by the Royal Netherlands Navy.

I-Mast

The entire mast was what would be called in shipbuilding terms ‘an owner’s supply item’. It was built of steel by the Naval Dockyard. In spite of the weight aloft, steel was preferred over aluminium or composites for its excellent fire resistance. The mast was then shipped to Thales Nederland in Hengelo for the fitting of the sensors suite. After thorough testing at the Thales land base, the entire mast was shipped to Flushing, where it was mounted on the Holland, and connected to the onboard network. The mast is a new type of mast, dubbed I-Mast – for integrated mast – from Thales. It concentrates all sensors, antennas and radars in one structure, without blind sectors. This is achieved by using four fixed directional radars instead of the rotating type. All antennas and radars can now be used simultaneously without interference. Another advantage of the I-Mast is that it reduces the installation time on board. The mast is pre-assembled away from the shipyard and can be installed and connected in a relatively short timeframe. Structurally, the mast is joined to the superstructure by bolts and epoxy castings.

Voluntary class

While compliance with SOLAS regulations and class rules is not required for navy vessels, the Dutch Navy has for many years built code- compliant ships on a voluntary basis. When the rules conflict with operational requirements, the Navy applies for exemptions. An example is the colour of the rescue boat: it is not surprising that the mandated bright orange does not match well with the stealthily coloured hull. The Holland class is built under Det Norske Veritas Navy class rules, as their set of rules is most relevant for this type of ship.

The OPV Holland now sails under the management of DMO. In a few months, when all the tests for the sensor equipment are completed and the crew is fully trained, the ship will be handed over from the DMO to the Royal Netherlands Navy and will receive the ‘Her Netherlands Majesty’s Ship’ prefix. The three other vessels in this class, Friesland, Zeeland and Groningen, are currently under construction. All are named after Dutch coastal provinces.

Bruno Bouckaert