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Sigma class Corvette

The SIGMA ship class is a design of Damen Schelde Naval Shipbuilding to built a Frigate or Corvette. This design is special for the export. SIGMA stands for Ship Intergrated Geometrical Modularity Approach. This design is special to be built in modules and easy to built by the wishes of the client. So by a easy way to different variants of the propulsion, sensors and armament. The hull design is a combined effort between Marin and Damen Schelde Naval Shipbuilding. This resulted in a hull that can be built in modules between 52 and 98 meter and from 400 to 1930 tons.

Damen has three basic models, 6910, 8313 and 9113 model. The design nomenclature indicates the beam of the ship in meters [the basic models having a beam of 10 meters and 13 meters, while the initial numbers indicate the ship's lenght, 69, 83 and 91 meters]. Orders for lengthened ships based on this design are also possible. A systematic hull form series has been set up, which has extensively been model tested on hydrodynamic performance. This has resulted in an optimal hull form series, ranging from 50 to 150m in length and 9 to 15m width. With this range, the whole spectrum from Offshore Patrol Vessel, via corvette to frigate is being covered. The vessels have been built up in a standardised modular way, using off the shelf equipment where possible. This approach allows the client to compose its own vessel of standard blocks. Of course every vessel can be further customised, based on specific client requirements like amount of equipment, type and make.

Two clients were initially found for the SIGMA type, Morocco and Indonesia. Indonesia bought 4 ships of the 9113 type, the last one delivered in 2009. These ships armament is, 1 76mm gun, Exocet surface to surface missiles and Mistral surface to air misiles. Morocco ordered two 9813 type and one larger type 10513 [that is, 98 and 105 meters long, with a beam of 13 meters].

For the client this SIGMA Design Philosophy offers the following advantages;

  • Flexibility in establishing the optimum arrangement of the clients current operational requirements, whilst maintaining the possibility to implement the changing needs of tomorrow.
  • Easy implementation of modifications or upgrades in the future, avoid premature obsolescence of the vessel.
  • Affordability by making use of standard equipment where possible. For every vessel the basis is being formed by a repetitive design, allowing for lower engineering cost. Due to the modular set up of the vessel, standardized production methods are being applied.
  • Wide selection of hull dimensions and different combat suites, all making use of proven product compositions.
  • Short lead time for engineering and construction, achieved by the modular set-up and standardization.
The Sigma design uses standard, 7.2-meter-long (24-ft.) sections separated by bulkheads with watertight doors throughout the ship. By varying the number of sections, a ship can be stretched or shortened. The Indonesian corvettes have 12 sections; two of the Moroccan ships have 13, and the third Moroccan ship has 14. The length of the sections was set at 7.2 meters because of an international requirement that 6-meter-wide damage be survivable. Based on the 7.2-meter-section principle, such damage will result in a maximum of two sections being flooded, which is survivable. The section dimensions also provide an extra margin to accommodate standard 20-ft. containers. Thin-hulled ships such as the Sigmas use 5-mm. steel rather than the 6-12-mm. steel used for patrol ships of the Dutch navy or Swedish coast guard.

Moroccos order for three Sigma multimission frigates from Schelde Naval Shipbuilding confirmed the value of the ships modular-hull design. The Royal Moroccan Navy signed the contract with Schelde on 06 February 2008 for approximately 510 million ($816 million). The pact calls for the design, build and delivery by 2012 of three surface combatants that the Moroccans are designating multimission frigates. Four missile corvettes built with the Sigma design had been sold to Indonesia, but some observers had dismissed the deal as a case of an old colonial power selling military equipment to a former possession.

The Morocco contract called for one 2,300-ton ship (designated Sigma 10513) that will be 105 meters long, with a beam of 13 meters. The other two ships will have a displacement of 2,100 tons (Sigma 9813s) and a length of 98 meters. The stretched version will have additional facilities for command and control, and accommodations for 110 personnel. The other two ships will have a crew of 91.

Apart from the standardisation, the quality and competitiveness of the SIGMA series are further enhanced by Damen Schelde Naval Shipbuilding extended experience in applying a clever mix of commercial and military standards. This experience has been built up in the RNN's innovative programs over the last 25 years. This approach is now being applied onto the SIGMA series and allows the client to make a balanced selection of commercial and/or military standards and specifications, that matches his operational requirements.

Royal Schelde presents its new range of Naval Patrol vessels based on its unique and highly innovative Ship Integrated Geometrical Modularity Approach, in short 'SIGMA'.
The driving factor behind the SIGMA-approach is to respond to the world market's demands of today and the next decades, emphasising notably the following two aspects:

  • Flexibility in establishing the optimum arrangement of the customers' current operational requirements, whilst maintaining the possibility to implement the changing needs of tomorrow, which may require modifications or upgrades, thereby avoiding premature obsolescence of the vessel;
  • Affordability, by a balanced trade-off between required capabilities on the one hand and initial procurement and subsequent life cycle cost on the other hand.

To achieve this goal the SIGMA-approach is in essence customer-oriented:

  • It provides a wide selection of basic versions with a vast range of options to enhance and customize the vessel without deviating from the proven product composition;
  • It allows a competitive price and speedy delivery.
Modularisation in naval shipbuilding is usually limited to using standardised pallets and containers. However, the associated advantages of this building method (risk reduction, shorter building time) can better be achieved otherwise. Royal Schelde chose to go a radically different way, by defining a set of geometric parameters, which are now applied throughout the entire SIGMA-range, thus providing a repetition of identical units, both in the dimensioning of the ship's spaces and in the lay-out of systems.

To validate the geometric modularity applied to the hull in the SIGMA-approach, a large number of tank tests has been conducted in a joint research program, conducted by the Marin institute and Royal Schelde's engineering department. The prime aim of the research was to establish to what extent it is possible to apply geometric modularity to hull shapes by applying parallel mid ship sections - and this without compromising the hull's hydrodynamic highspeed displacement characteristics. The tank tests resulted in the dimensioning as specified in the tables below, with a basic series covering patrol vessels in the range of 52 m to 98 m length over all, with displacements ranging from 440 tonnes to 1930 tonnes. In the Schelde Naval Patrol-series, each specific configuration is indicated using a four-digit number, designating its approximate length and breadth overall in meters.

The Schelde Naval Patrol-series marks a breakthrough in ship design and sets the trend in naval shipbuilding today and tomorrow.

In the SIGMA design approach the mission of the ship such as "Customs / Police", "Coast Guard / Offshore Patrol", "Littoral Warfare" or " Blue Water" mission profiles, determines the Combat System configuration, the ship's speed, the maximum range, the crew size and the mission time. These elements in turn determine the ship's hull and topside. Royal Schelde cooperates with all reputable combat system and weapon suppliers and can configure and deliver on a turn-key basis the optimum combat system, that matches the ship's mission profile.
Standardisation apart, the quality and competitiveness of the Naval Patrol series are further enhanced by Royal Schelde's vast experience in applying a clever mix of commercial and military standards and specifications, which it has built up in Royal Netherlands Navy innovative programs since the late eighties.
The four Royal Netherlands Navy Air Defence Command Frigates are designed and built by Royal Schelde using navalised commercial equipment and techniques made suitable for naval application. Yet these Frigates meet the most demanding operational and technical requirements. This approach is now projected onto the Schelde Naval Patrol vessels and allows the customer to make a balanced selection of commercial and/or military standards and specifications, that matches his operational requirements.
Propulsion options include twin screw controllable pitch propeller or twin water jets, driven by two or four diesel engines and twin screw fixed pitch propellers or twin water jets, full electric driven by four to six DG-sets. Other options, e.g. including gas turbines, are available.

  • Proven and tested hull form series
  • Straightforward layout and throughout internal accessibility
  • Ergonomic bridge layout with optimal panoramic visibility
  • Hangar optional
  • Low-Spray-Bow optional

  • Bilge keels (limited roll reduction)
  • Fin stabilization (speed dependent)
  • Roll stabilization tank (also at low speed)

  • Signatures:
  • Noise attenuation, flexible mountings
  • RCS shaping
  • IR shielding
  • Magnetic degaussing
  • Watertight integrity:
  • No access doors between compartments below bulkhead deck
  • Progressive flooding prevention
  • Shock: functionally optimized
  • NBC protection: citadel, NBC-filter
  • Redundancy in essential services by layout and duplication
  • IMO
  • Naval 80 knots wind
  • Naval 100 knots wind
  • Naval, two-compartment damage

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