This is an edited article originally from ‘This is Napier’ No.5 1959
During 1957 the Compania Shell de Venezuela took delivery of three high-speed passenger launches for service on Lake Maracaibo between land bases and oil rigs up to 40 miles offshore. The launches, designed and built by John I. Thornycroft & Co. Ltd of Woolston, Southampton, were powered by two Napier Deltic 810 b.h.p. 9-cylinder high-speed marine diesel engines, carried up to 50 passengers and had a cruising speed of more than 30 knots.
In August 1959 Shell took delivery of a larger and still faster passenger launch for service on Lake Maracaibo. Numbered PL4 this was designed and built by Vosper Ltd of Portsmouth and powered by two Napier Deltic 18-25K high-speed marine diesel engines; had a cruising speed of more than 35 knots; accommodation for sixty passengers, and could operate between the shore bases and oilrigs 75 miles out.
These four fast launches maintained a continuous 24 hour a day ferry service between the shore and the rigs. Oil workers earned high wages, and time spent in transporting them from shore to rig and back had to be paid for by the oil company. Ordinary launches wasted too much time; helicopters were uneconomic; only a fast diesel engined launch was a sound proposition, and only the compact “Deltic” fitted the launch’s specification.
Vosper’s design team visited Maracaibo to study operating conditions on the spot. They saw that a high steering position was essential since Lake Maracaibo was littered with half-submerged tree trunks and other debris brought down by the rivers that fed it. The helmsman had to be situated so that he could see these navigational hazards at the earliest possible moment. It also became clear that the boat needed the most sensitive and responsive steering system possible, so that the helmsman could avoid an obstruction by the flick of a finger. PL4 was also designed so that it could go astern from full ahead by means of a single movement of a single lever, so that obstructions too large to be avoided by a change of direction could be avoided by a rapid loss of speed.
Proof by demonstration
Shortly before the Vosper boat was shipped to Venezuela, representatives of the technical press inspected PL4 on the Solent. The steering position was described as “so high that I seemed to be sitting in the Eiffel Tower” and that the helmsman “ought to be able to see a champagne cork at two hundred yards.” When put into reverse PL4 lost all forward speed in just two boat lengths.
Construction and equipment
PL4 had an all-welded steel hard-chine hull; tests showed that it did not suffer from “slamming” in a seaway, as many hard-chine boats did. The superstructure was of welded aluminium alloy, and the passenger accommodation was pleasantly furnished and lined with light green Lionide. Ventilation trunking with directional punkah louvres were fitted throughout the passenger saloon, the ventilation air being supplied by two centrifugal fans. Electrical power came from a 1.5kW 24V D.C. Lister generating set floating 24V 130 ampere hour battery made by the D.P. Battery Company. The equipment included searchlights for night operations and a “Ranger” marine-type ship-to-shore wireless set by Pye Telecommunications Ltd. The steering equipment supplied by Mathway Marine of Hamble, Hampshire was normally electro-hydraulically assisted, but could be operated manually in the event of a power failure