Title: Points Of Reference
Pages: 48 - 53
Author: David Rowlands
Points Of Reference
Developments in lighthouses, lightships and the growing use of helicopters are described by David Rowlands
Britain's waters are among the busiest in the world with about 350 ships a day using the English Channel alone and about 210 ferries a day linking British ports with Europe. Like other major transport arteries, the sea has its signposts: the lighthouses, lightships, and navigation and wreck-marking buoys which are the responsibility of Trinity House.
Formed in 1514 to provide a pilot service and charged in 1836 with maintaining all navigation aids, the Corporation of Trinity House has in the last eight years begun an overhaul of equipment and methods that is now resulting in major changes to the appearance and operation of on- and offshore hardware.
Offshore, the mainstays of Trinity House's operation are the 27 distinctive red-painted lightships backed by a reserve of three ships that makes this one of the world's largest lightship fleets. Manned by crews of 11 each, of which seven are at sea at a time, the ships are very expensive to maintain: about £30 000pa. New lightships cost in the region of £250 000.
An alternative to these costly sea stations is the Large Automated Navigational Buoy (Lanby), first developed in America from successful unmanned oceanographic research platforms. Trinity House now has five Lanby buoys, four designed in America by General Dynamics and the fifth a British design by Hawker Siddeley Dynamics. Lanbys cost in the region of £195 000, including the setting up of onshore facilities for their automatic control; annual servicing and operation, at £3000pa, is one-tenth that of a lightship.
The Hawker Siddeley Lanby was stationed on the Shambles. Trinity House's experience with this jointly developed design has not been happy. A 'buy British' policy and a belief that the General Dynamics buoys then available were not up to Britain's arduous offshore conditions were behind the design of this 12m 40ft) diameter discus buoy built for 30-300ft moorings in 60km/h Bales 12m (40ft) waves and 7 knot currents.
It relied on three diesel engines, each working a day-long stint in a continuous 72h cycle of battery charging, to operate a group of sealed-beam lamp units revolving at the top of its 12m tower, which also carried a Wallace & Tiernan foghorn audible at 6km.
Three years experience with this buoy has shown it to be more sophisticated than is required: it has complicated automatic control mechanisms for regulating the engine change and a multiplicity of back-up systems in case of failure of any main units.
The four General Dynamics Lanbys now in service have shown that two British-made diesel generator sets are sufficient and that automatic cycling is not necessary. One engine will run for six months unattended and the other is only given a short run once a month, automatically started, to ensure it is ready for emergencies.
The other major fault of the British buoy was its AGA revolving light which did not prove to be robust enough to withstand the high acceleration forces experienced in very rough seas; six months' unattended operation was not possible. The American designed Lanby (actually built in Britain with about 50 per cent American equipment) uses fixed xenon flash tubes. These tubes suffer the disadvantage that their high-intensity short flash can be missed in the blink of an eye. A revolving light beam can often be seen throughout its revolution and the flash has greater persistence.
The Hawker Siddeley buoy is now back on Cork Hole (the Trinity House experimental mooring off Harwich where DESIGN first visited it) with a new navigation lamp that may overcome the problems of both sealed-beam and xenon flash units. This Trinity House design has a continuously burning mercury arc lamp, a revolving aluminium carriage and multilensed panels.
Another alternative to lightships is a new type of offshore lighthouse which resembles an oil-drilling platform in concept and construction. The first example of this lighthouse replaced the Royal Sovereign lightship eight miles off Beachy Head in 1971. Built on Newhaven beach and floated to its position, the lighthouse consists of a broad concrete base, supporting a concrete tower in two telescopic sections which support a cabin section and light 37m above the surface. The cabin roof provides a helicopter deck, in one corner of which is a steel-lattice tower, bearing the 22 million candela lamp inside a revolving cage of lenses.
Equipment includes four 20kW diesel generators, three diesel compressors to power the diaphone foghorn, radar to monitor shipping and the nearby Greenwich Lanby, three-man crew quarters and rooms for visiting technicians.
The Royal Sovereign platform, its light visible over 40km away and the foghorn audible for 8km, has been a successful venture largely as a result of its helicopter deck which ensures that the crew rarely miss their monthly changeover.
Trinity House's single Bolkow 105D twin-engined helicopter, recently hired from Management Aviation instead of the heavy Wessex 60 previously used, is small enough to land on special platforms like that constructed on the Wolf Rock lighthouse.
This 7.6m diameter platform, an aluminium deck supported on a steel lattice, is designed to fit securely onto the top of the lighthouse tower over the light. Careful detailing of the attachment to the lighthouse's granite blocks was necessary as high seas forcing upwards on the deck panels could exert enough force to remove the entire platform. The Wolf Rock deck has proved a success and Trinity House is now considering whether or not to extend helicopter service to the famous Longships, Eddystone and Bishop Rock lighthouses off the Cornish coast. Another venture is to fit similar decks to lightships.
Just outside Southampton Water is the Calshot Spit lightship which is another experiment to relieve Trinity House of the enormous cost entailed in keeping men afloat. A conventional light vessel in appearance, the Calshot Spit light is unmanned and operated by the same automatic methods employed for Lanby buoys: Trinity House thinks this may be one way to overcome the 25 year time-lag it faces in replacing all the lightships off Britain's coasts with more maintenance-free equipment.
Lights apart, the other half of Trinity House's responsibility is the provision and maintenance of navigation and hazard-marking buoys. Buoyage systems throughout the world are in a state of the utmost confusion to the mariner; there are two main systems in Europe alone. A recent experiment carried out by Trinity House for the International Association of Lighthouse Authorities is attempting to unify the systems for world-wide use.
The two European systems are known as the 'lateral' and 'cardinal' types. Lateral-system buoys, are used for channel marking; they indicate by colour, usually red and black, that they should be left to port and starboard respectively when sailing in the direction of the incoming tide. Cardinal-system buoys, denote isolated dangers and show by distinctive topmarks in which compass direction from the danger they lie. Off the coasts of other countries, buoys with the same types of topmarks may be used for other applications.
The new IALA system combines the best features of both main types of current buoyage: by using distinctive buoy shapes and colours, light-flash sequences, light colours and topmarks, a uniform system has been assembled to allow mariners to distinguish channels and hazards without local knowledge of which system is in use. The main obstacle to rapid identification of buoys in the lateral system is the convention of denoting port and starboard in the direction of the incoming tide; under the new system, all channels will bebuoyedwithrespect to a compass direction.
The system regards wrecks in the same way as other isolated hazards; the familiar green wreck buoy would be replaced by a buoy indicating compass direction to the hazard.
A spate of serious accidents in recent years has led to the nowobligatory directive to ships to use the Dover Strait traffic separation system. Half the world's shipping accidents happen in this narrow neck of water which carries north-south traffic between the world and Europe's largest tanker terminals and container vessel ports. At right-angles to this flow of vessels is the constant plying of car ferries and other smaller craft between British and. European ports.
The lane system, set up by the UN's Inter-governmental Maritime Consultative Organisation three years ago, directs northbound ships to the French side of the Channel and southbound ships between the Varne Bank and the Channel Ridge on the English side of the water. Objections to the present system come from ships trying to enter the Thames estuary across the traffic flow and channel ferry operators who say that the system adds ten minutes to their direct Dover-Calais/Boulogne routes. Convictions of rogue ships ignoring the lanes numbered 80 last year.
HM coastguards who police the system for IMCO report rogue ships by radio every two hours during routine weather and hazard broadcasts but still the captains ignore the rules. Their main reason for doing so is ultimately to cut sailing time but many say that grouping ships together increases collision hazard enormously. HM Coastguard and IMCO are satisfied that the system works - there have been no serious accidents since it began.
Above crew of a Trinity House lightship being replaced by helicopter as an experiment. Lightships are being gradually replaced by automated Lanky buoys opposite because of cost of crowing and maintenance. Five Lanbys have been built: the first with the conical shaped base was British, stationed on the Shambles; Trinity House then turned to an American design far right Right a light could have saved the Granite State wrecked off Porthrurno in 1895
Far left medieval lighthouse on the Isle of Wight Opposite top original Eddystone lighthouse dating from 1699 differs very little in basic design to the most recent lighthouse such as the Royal Sovereign above Opposite bottom St Catherine's lighthouse, Isle of Wight, built at the beginning of Queen Victoria's reign and stir in use Left clean lines of the Dungeness lighthouse
1) lateral system wreck buoys are all green and indicate whether it should be passed on the left or right and if it can be passed on either side
2) the cardinal system shows whether it should he passed to the E or W
3) in the IALA experimental systems wrecks will be marked the same as any other obstruction, buoys indicating by their shape and colour in which direction the wreck is
Opposite the Wolf'Rock lighthouse has to come in for some battering. A model of the tower with a proposed helicopter landing platform is tested in a wind tunnel at the National Physical Laboratory, Teddington. The helicopter platform has since been built on to the lighthouse
Above right a Decca Radar picture of Dover Strait showing the French and British coasts, over 50 north and south-bound ships in 'lanes' and a wreck about one third of the way off the British shore