Marine Link
Thursday, January 18, 2018

Military Designs for the future

Gone are the days when navies were restricted to ordering monohulls. Although traditional hulls are still popular with military forces the world over, today's European design teams are emerging with intriguing multihull designs which claim to offer significant advantages. Blohm + Voss in Germany, Vosper Thornycroft in the U.K. and Kvaerner Mandal in Norway all have new concepts for the naval vessel of the future.

Blohm + V on The Mekat air-cushion catamaran, the latest product to spring from Blohm + Voss's MEKO (multipurpose combination) unique modular warship construction principle, is now truly off the design board and afloat as the prototype vessel Corsair.

An air-cushion catamaran (i.e. the combination of a catamaran with its two hulls and an air cushion craft), the Mekat series is available in three versions β€” the 80,150 and 200 β€” all of which are suited to military and paramilitary requirements. The largest β€” the Mekat 200 β€” is 146.3 ft. (44.6 m) long x 45.6 ft. (13.9 m) beam with an on-cushion draft of 2.6 ft. (0.8 m).

Two propulsion options are available: diesel to achieve speeds of around 40 knots and gas turbines for approximately 50 knots.

Operating in typical surface ef- Blohm + Voss' SES Corsair offers military operators a host of advantages.

feet ship (SES) fashion, the vessel has forward and aft skirts to seal off an air cushion located between the two hulls. The cushion is fed by highly efficient radial fans which cause it to lift the vessel so that only 15-20 percent of its weight is borne by the water.

In addition to high speed and low draft during on-cushion mode, the glass reinforced plastic (GRP) built Mekat reportedly produces reduced pressure, infra-red, noise and electromagnetic signatures. Furthermore, its catamaran shape provides a large deck area which can be used to accommodate customer-specified modules from the MEKO range.

Voipar Thornycroft Leading U.K. military vessel builder Vosper Thornycroft (VT) has also revealed details of two new vessel designs β€” one as a trimaran type and the other available as an SES or monohull. VT has tailored both primarily to the requirements of Middle East navies, as it is well versed in their specific needs, having secured considerable business with Gulf military forces.

VT chose the IDEX 95 exhibition in Abu Dhabi as the launch pad for its new concept patrol/mine /countermeasures vessel (PMCM) and trimaran corvette. As VT Technical Director Bob Mulligan explains: "They are flexible, efficient designs that are also cost-effective. As navies continually look towards matching their needs with the budgets available, we believe these designs are the way ahead." Flexibility is obvious with the PMCM. Built in GRP, it can He constructed as a SES or monohull and is specifically aimed at customers who cannot devote resources to a dedicated MCM but would welcome a vessel that can also undertake patrol and hydrographic survey tasks.

Its basic configuration is, therefore, as a patrol vessel with ability to be re-programmed for MCM or other roles when additional equipment is fitted and, for this purpose, has been designed to the same shock standards as the modern MCM vessel.

At about 164 ft. (50 m) long, the vessel will be capable of speeds up to 25 knots (unusual for an MCM) with a slow speed range between zero and 12 knots and a range at 12 knots of 2,000 nm. For MCM duties, a variable depth sonar is fitted and a Ships Positioning Control System with navigational aids necessary for MCM/policing duties also incorporated. The second design β€” a 311.7-ft.

(95-m) long trimaran corvette β€” is the product of much investigationn t o the benefits of the large trimaran for naval use. Advantages lie with low resistance and flexibility of layout. The former bonus means that either higher speeds than a conventional monohull can be offered for the same installed power or t h a t speed can be matched with lower power requirements.

Layout has been another major consideration as for a trimaran of about 311.7-ft. waterline length, the cross deck structure between the main hulls is sufficient to accommodate a full deck. This provides useful volume in the center of the ship where space is most valuable thus making layout of accommodation spaces more flexible.

Having an open deck above the wide cross structure is for a helicopter flightdeck. The closeness of this flight deck to the pitching center of the vessel will significantly reduce the motion and thus extend helicopter operations to higher sea states.

It is understood that VT has received a good amount of interest in the new designs. The company, though, is currently keeping busy with 14 newbuild contracts on its books, including: seven 170.6-ft. (52- m) Sandown Class GRP minehunters for the Royal Navy; four 183.7-ft. (56-m) fast attack craft for Qatar which are loosely based on the Vita class, the first of which is due for launching in the spring; and final fit-out of the second of a two vessel A1 Jawf class order for the Royal Saudi Naval Forces. The yard also awaits confirmation of three more of this class for Saudi and is also tendering for frigate orders from the UAE and the Royal Navy, U.K.

Production is also on schedule for a second 272.3-ft. (83-m) corvette in build for the Royal Navy of Oman with the superstructure lowered into place in early January.

Kvaerner Mandal Norwegian yard Kvaerner Mandal is working on an order for nine mine countermeasures vessels for the Royal Norwegian Navy (RNoN). Here, designers return again to the unconventional as when delivered, the RNoN will have the first fleet of operational SES MCMs in the world.

At 181 ft. (55.2 m) length by 44.5 ft. (13.5 m) beam by 2.95 ft. (0.9 m) draft on cushion, the designs are claimed to offer better operational performance, survivability and economy of operation than comparable monohulls and catamarans and, as 75 percent of the displacement is airborne, the transit speed is increased by more than 50 percent. Not only can they operate in shallow waters, but their maneuverability is reportedly superior due to the long distance between the twin hulls, which gives a large turning moment from the wateijets. The vessels are also able to move sideways without any rotation or forward movement.

The main propulsion and auxiliary plant are housed separately in unmanned machinery spaces, one over each hull just abaft midships. Each room houses an MTU 12V366 TE84 diesel engine developing 1,500 kW (2,040hp) at 1,900 r pm driving a Kvaerner Eureka waterjet with azimuthing nozzle for steering and a reversing bucket. For slow speed operations the wateijets are hydraulically powered via pumps. Vessels are equipped with two independent sonar systems which enhance safety and improve detection of mines when operating in mined waters.

Due to the improved seakeeping of the SES, the hazard involved in deploying divers or remote operated vehicles in adverse weather conditions is reduced. As the vessel has waterjets instead of propellers and rudders, the operator is free to maneuver the ROV without the risk of entangling the umbilical. Sonar conditions are also improved as less turbulence is created and the danger zone reduced as vessels can come close to target. Added to this, the open deck area combined with moderate roll angle maximizes safety for mine sweeping operations

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