Canadian naval architects and consultants Robert Allan Ltd were responsible for the design, working in close co-operation with Ostensjo's technical consultant Carl J Amundsen.

The design brings together many recent innovations and highlights a high level of co-operation between the owners, designers, builders and propulsion specialist Voith. The same design team were responsible for the larger and highly successful escort tug Ajax introduced by Ostensjo in 2000 and many of the features introduced in that vessel are incorporated in this latest new tug. Astilleros Gondan SA was entrusted with the task of building this new and in some respects unusual vessel. For a yard better known for high quality research and fishing vessels, merchant ships and even 'super yachts', this was their first tug. Co-operation and build quality is evidently of a very high standard and has resulted in a repeat order, with delivery scheduled for the end of this year.

Velox is a vessel of 37m in length overall with a breadth of 14m, and a maximum draft at full load of 6.9m. The tug has been constructed to meet the demanding requirements of DNV +1A1 Tug, EO, OILREC, FiFi 1 Escort(130/10).

A highly developed and unusual hull design incorporating a bulbous bow, sponsons and bilge keels is optimised to operate effectively while moving ahead or astern and achieve very high steering forces, when operating in the escort (indirect mode), unprecedented in such a small vessel.

Also incorporated in this new compact escort tug design is a specially designed skeg (fin) incorporating the very first 'Voith Turbo Fin' (VTF) concept.

Intended to maximise 'lift' and provide very high steering forces, when the tug is operating fin-first in the escort role, the deep vertical skeg has a rotating cylinder fitted within its leading edge (the leading edge when travelling 'skeg first'). Voith claim that in this instance an increase in steering forces of approximately 30 tonnes will be achieved in a vessel much shorter that the larger Ajax . The rotating cylinder in the skeg's leading edge provides a much improved boundary layer flow and a resulting increase in 'lift'.

Direction of rotation is critical and is automatically adjusted to suit the tug's angle to the towline - to port or starboard. Sensors in the control console of the Voith propulsion system activate the 'Turbo-Fin' and apply the appropriate direction of rotation when towing fin-first in the escort mode, when a certain power setting and helm angle is detected. The cylinder fitted in the skeg of Velox is 0.8m in diameter and 3.7m high, extending vertically from the base of the skeg. A hydraulic motor of only 45kW is required, mounted directly above the unit, and the cylinder has a maximum rotational speed of 245rev/minute. Hydraulic power is supplied by the vessel's main hydraulic system, powering the deck machinery and other ancillary equipment.

Two Voith Schneider six-bladed 32R6/210 propellers of the very latest type are installed in the vessel and powered by two Rolls-Royce - Bergen C25:33L8P main engines. The eight cylinder diesels produce a total of 6530bhp (4880kW) at their maximum continuous rating of 1000rev/minute. A static bollard pull of 65 tonnes was achieved on trials along with a maximum free-running speed of over 14.5 knots. Maximum steering forces, while operating in the indirect towing mode at 10 knots, of 140 tonnes are anticipated and maximum braking forces of 150 tonnes.

The actual performance figures for steering forces will be determined in due course when full-scale trials are conducted underway with a suitable tanker under DNV supervision to verify the vessel's escort tug notation.

Electrical power is supplied by two identical Volvo-Penta auxiliary diesels driving Stamford 135kW alternators rated at 400v/220v at 50Hz.

Hydraulic pumps for the main deck machinery system, and the fire pumps are coupled to the forward end of each main engine via Kumera-Norgear step-up gearboxes. A harbour generator has proved unnecessary when operating at Sture due to the adequate provision of 'shore power'.

Substantial 'box-coolers' on the port and starboard side of the engineroom provide not only cooling for the main engines but also auxiliaries and other services. Also located in the engineroom is a high capacity ballast water transfer system.

The system enables ballast to be transferred between the main internal tanks fore and aft and is equipped with pumps and valves controlled remotely from the main 'touch-screen' monitoring and alarm panels in the engine control room, ships office and wheelhouse. Two main ballast tanks and two small heeling tanks have a total capacity of 148m 3. A maximum of 213m 3offuel oil can be accommodated, 23.9m 3of fresh water, 23.4m 3offoam compound and provision is made to store up to 146.5m 3of recovered oil. The very deep skeg contains some 35 tonnes of permanent ballast in the form of steel pellets and the 'Turbo-fin' cylinder is a free flooding structure.

Below decks, the hull is sub-divided, with bulkheads and hydraulically operated watertight doors at the after end of the engineroom and between the engineroom and the Voith propulsion machinery room. Aft of the engineroom is a sizeable store, accessible from the deck and capable of housing the oil recovery skimmer, towing gear and other equipment. A further bulkhead, with a manually operated watertight door, is located between the Voith room and the forward hull, where a fitness room and a dry store are situated.

Towing equipment provided enables the tug to carry out escort operations and general shiphandling duties. The hydraulically powered Karmoy towing winch has two large 'split' drums, on a common shaft, and has a maximum line pull of 200 tonnes and a 300 tonne brake holding capacity.

Each drum is fitted with a high performance Steelite man-made fibre towline of 92mm diameter and 350m in length. One towline can be replaced by a 1000m steel wire towline should it be required. The winch is operated from the wheelhouse and can be used to control the length of towline and the maximum load applied automatically, during escort operations. A single spooling gear mechanism is fitted and designed to be set-up for use with either drum.

The towing staple (fairlead) is very unusual. Designed to accommodate both steel wire and a synthetic towline, it was necessary to have two separate apertures that will function effectively in both escort and towing roles. The result is a very wide-based channel slot to accept the fibre towline during escort operations, with a central fairlead above for use with a steel towline. The lower slot permits the line to migrate far outboard towards the pressure side in an indirect operation, thus reducing the heeling moment on the tug and increasing the line tension capacity. The long fairlead slot is very close to the deck and lined with stainless steel in the normal manner.

Other deck equipment supplied by Karmoy includes specially designed towing pins on the after bulwarks, a capstan and anchor windlass. A hydraulically powered Effer 44000-3SL knuckle boom crane, complete with a winch and wire lifting mechanism is fitted on the starboard side of the winch fairlead, for use in handling stores, towing gear and deploying a skimmer.

Fire fighting equipment fitted to meet the FiFi 1 standards includes two Unitor monitors located at boat deck level. One monitor is capable of delivering 20,000 litres/minute and the other water/foam at the same rate. Two pumps driven by the main engines are rated at 1,500 cu/m/hour to supply the monitors and the mandatory self-protection spray system.

Provision is made aboard Velox to rig spray booms on either side of the vessel for dispensing chemical dispersant and to deploy a skimmer and a protective boom. The skimmer is stowed below deck in the equipment store and accessed via a hatch in the deck. A hydraulically powered reel, located within the superstructure on the starboard side houses the protective floating boom and its inflation/deflation mechanism. When in use, a large hatch is opened in the side of the deckhouse allowing the boom to be pulled out - over the starboard bulwarks.

The wheelhouse is designed to afford good visibility when operating bow or skeg first and the controls are optimised to afford the tug master the best possible control position when operating in the escort mode where maximum concentration is required. Controls for the Voith propulsion system follow the now common configuration used in escort tugs, with the relatively small steering wheel on one side of the split console and the power/pitch controls on the other. Navigational equipment includes two Furuno radars, a gyro-compass, auto-pilot, electronic charting, DGPS, an echosounder, log and Navtex. The communications outfit meets the GMDSS and IMO standards for use in Sea Area A2.

Velox is fitted out to the highest standards for a crew of up to six persons in fully heated and air-conditioned accommodation. Five of the six single cabins include private en-suite facilities and a spacious lounge/mess room is supported by a modern fully equipped galley. The ship's office/meeting room houses a wide range of computers, communications equipment and has access to the ‘Bjorga’ computerised machinery monitoring and alarm system. A well-equipped fitness and exercise room is provided for the crew, below decks in a compartment aft of the fore-peak.