Trans RINA, Vol 152, Part A2, Intl J Maritime Eng, Apr-Jun 2010


obsolete wooden walled battleships. Normandie Express was built in 2005, aluminium hull, 38,500shp medium speed diesels with four waterjets, 42 knots, 850 passengers, 235 cars.


Transport of passengers is today focussed on short sea and local ferries, with a huge variety of designs, usually including vehicle transport. Sizes now exceed yesteryear’s


deep sea liners, 50,000gt being


technology for fast warships, permitting high power in a compact space, with lesser manning and maintenance from the 1970s. With gas turbines being of


lower not


uncommon on some European routes, at over 20 knots. From the 1960s, high speed craft began to challenge conventional ferries on short routes, initially air cushion vehicles and hydrofoils with speeds of 35-50 knots. With their inherently low lift/drag ratio, light


alloys were


needed to keep hull weight down and gas turbines were often used to provide the high power. Steady growth has continued, with some craft now carrying around 1500 passengers and 400 cars at speeds of over 40 knots. But it is the catamaran concept that dominates the fleet today, where two slender hulls offer low drag while the bridging structure offers space. Medium speed diesels have often proved more economical than gas turbines, with both types of prime movers coupled to the ubiquitous waterjet (up to four). Freight-only high speed craft have yet to challenge conventional ro-ro’s on short sea routes. On deep sea routes, the problems of seakeeping, large fuel load and cost, and low payloads await technologies


to improve lift/drag ratio and


enabling fuel


consumption significantly – a problem that early aircraft also faced.


efficiency at modest cruising powers, it was common to fit two gas turbines per shaft, one for boost to around 30 knots, and one for cruise up to about 20 knots (sometimes diesel). The frigate Sheffield has three machinery spaces. Nearest the camera is the Aft Auxiliary Machinery Room with two diesel generators in the centre, two auxiliary boilers in front


of them with auxiliary machinery


modules and distillation plant at each side. The middle compartment is the Aft Engine Room, showing the two 5000shp Tyne gas turbines and forward the much bigger gearboxes. The further compartment


is the Forward


Engine Room, although the two 25,000shp Olympus gas turbines are barely visible.


Gas turbines have been the prime mover of choice for most high speed warships from the late 1960s, derived from aircraft jet engines, although the first seagoing (industrial) gas turbine was fitted in a British torpedo boat in 1947. High power-weight ratio, compactness, repair by replacement, reduced manning and quick starting have


for military vessels outweighed the


disadvantages of high fuel cost, few frame sizes, lack of reversibility (usually achieved by controllable pitch propellers), large uptakes and downtakes, and possible salt spray ingestion. Electric propulsion technology with high power density motors has increased the number of ships with full electric propulsion, especially those with a wide range of power commercial or offshore.


demands, whether Azimuthing thrusters


become the propulsor of choice for tugs, two giving great manoeuvrability under one-man control, hence a smaller crew.


While some high speed craft have been built of fibre reinforced plastic, a much larger market has been in mass produced leisure craft, where low maintenance has been an advantage. Its non-magnetic properties encouraged the use in mine countermeasures vessels from the mid 1970s. Fishing vessels have been built in the widest range of materials, also including timber and ferro-cement, but the stern trawler offering safer operation for the crew is usually built in steel.


Supporting technologies have had a collective impact on ship performance. Self polishing tin-based co-polymer anti-fouling coatings in the 1970s provided smoother longer life protection, a capability now offered by foul release (non-stick) coatings since the ban on TBT-based coatings in 2003. Inert gas systems cargo tanks


for hydrocarbon from the 1960s improved the safety of Figure 14. Gas turbines were an important enabling


tankers, based initially on scrubbing flue gases from boilers. Automation starting with auto-pilots has reduced crew number down to half a dozen on coastal vessels and around a dozen on some deep sea ships with dual trained deck and engine crews. Improved navigating aids have helped reduce ship casualty rates, although both the quantity and quality of experienced seafarers continues to


naval, have


©2010: The Royal Institution of Naval Architects


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