Continuing a series of profiles of lifeboat classes By Keith Thatcher RNLI Naval Architect TI he RNLI's experiment with an in the Waveney class proved to Institution turned its attention to tended service offshore.

entirely different concept of lifeboat be an unqualified success, and the a larger, faster boat capable of ex-The Waveney had not been considered atrue All-weather lifeboat, although time proved this to be an incorrect assumption, and the Committees felt there was a need for a boat of at least 50ft long capable of speeds in excess of 18 knots.

In common with many previous boats, Messrs G.L. Watson was commissioned to prepare the hull design, and they drew a 52ft, transom stern, semi-displacement hull with soft bilges and multiple spray rails at the waterline.

Re-drawn Model tests indicated the need for changes to improve sea-keeping and performance, and the RNLI's staff redrew the lines to incorporate extra beam and tunnels to allow larger propellers.

The multiple spray rails were also removed as they produced, rather than suppressed, the spray.

The prototype boat, Arun, was commissioned from Wm. Osborne of Littlehampton, a company which has a long history of RNLI prototype work, and launched in 1971. She was given the official number ON1018 and the operational number 52-01.

The material chosen for the first of the class was laminated wood, three skins of agba on laminated frames, a conventional boat building method. A period of extensive evaluation then followed during which Arun travelled the length and breadth of the country.

Many coxswains tried her and all were highly enthusiastic about her seakeeping and handling. A few old hands were initially sceptical about the drastic change of shape when compared with the old 'traditional' lifeboat and expressed concern about the exposed screws and rudders. A short trip soon removed any doubts however.

With the success of Arun a second boat was commissioned, incorporating significant changes above the waterline.

On 52-02 the sheerline was cut down to give barely 3ft of freeboard amidships and a re-designed wheelhouse gave two separate cabins above deck. An inflat-able shallow water rescue boat, the Y class, was carried on a gantry over the after deck with its own launching crane.

The engines were also uprated to give enhanced performance. The second boat in class, ON1025 Sir William Arnold, was launched in 1973 and, after initial trials, stationed at St Peter Port, Guernsey.

Lengthened The third boat, ON1037 Edward Bridges (Civil Service No. 37), was then built incorporating a further change to the hull. She was lengthened to 54ft and the transom corners radiused to produce an elliptical stern which, it was felt, would give better handling in following seas and also make the corners of the transom less vulnerable. The construction material was again laminated timber, identical to ON1018 and 1025. She was launched in 1975 as 54-03 and stationed at Brixham as the Torbay lifeboat.

With the launch of the third wooden boat, thoughts turned to production. It had always been the RNLI's intention to build the bulk of the Arun class from glass reinforced plastic (GRP) and a mould was now constructed, based on the hull of the latest boat ON1037, slightly modified to suit the new material.

Since the users of the boats could still not decide which stern configuration was best the mould was given a removable stern section to allow 52ft and 54ft boats to be built as required. This mould has been used for every Arun hull built since, with a single exception which we will come to shortly. All mouldings have been produced by Halmatic at Havant, near Portsmouth.

The first GRP-hulled boat, 54-04 Tony Vandervell ON1049, was launched in 1976.

To complement the GRP hull Halmatic developed a GRP superstructure which was almost identical in shape to the aluminium alloy house fitted to ON 1037. In general the change was successful, but the GRP structure proved slightly heavier and there were problems with radio interference, as GRP has little or no 'shielding' effect. A decision was therefore taken to revert to an aluminium house for boat number 9 (52-09, Spirit of Tayside ON1056) and the shape has remained constant since.

With boat number 8 (52-08 Joy and John Wade ON1053) the 52ft hull with transom stern was re-introduced, and the hull shape then remained unchanged through to the final boat, 52-46 The DukeofAtholl ON1160, which was completed in 1990.

All Aruns except for the three wood prototypes and one other mentioned briefly above, have been built in GRP.

The exception is ON1100 Snolda, which has a steel hull with aluminium alloy decks - her operational number of 52- 030 carrying the extra zero to denote steel or aluminium construction. This boat was built by Fairey Marine in 1985 as part of an investigation into a serious consideration for building the remaining boats from this material. The experiment proved a complete success and many coxswains consider ON1100 to be the best Arun for comfort and handling. However, cost defeated any chance of more steel Aruns; future boats would have cost almost half as much again as a GRP-hulled boat.

Arun construction has now ceased and work is progressing on her replacement, still known as FAB 3 (Fast Afloat Boat 3). ARUN CLASS 1971 - 52-01, ON 1018, first of class, wood, high sheerline 1973-52-02, ON 1025, wood, low sheerline 1975 - 54-03, ON 1037, wood, round transom, 54ft 1976-54-04, ON 1049,first GRP boat, GRP hull and wheelhouse, round stern 1977 - 52-08, ON 1053, transom stern reintroduced 1978 - 52-09, ON 1056, aluminium alloy wheelhouse reintroduced 1979 - 52-11, ON 1058, wheelhouse layout redesigned - open plan 1980 - 52-15, ON 1067, engines changed from D343 (6 cylinder) to D3408 (8 cylinder) and uprated to 485hp 1985-52-030, ON 1100, only steel-built hull, standard wheelhouse 1988 - 52-43, ON 1149, hull laminate changed, epacryn resin 1990 - 52-46, ON 1160, last Arun launched Introduced: Designed by: Number built: Number in service at November 1990: Launching method: Number of crew: Length overall: Beam: Displacement: Engine type: Maximum speed: Radius of action: 1971 G. L. Watson/RNLI (see text) 46 46 Lies afloat 6/7 (later boats) 52ft/54ft 17ft 25.25 tons (prototype) to 32.25 tons (steel) Standard GRP boats approx 31 tons 52-01 two Caterpillar 336 (375hp), 52-02 to 52-14 Caterpillar D343 (460hp), 52-15 to 52-46 Caterpillar 3408TA (52-15 to 52-41 485hp, 52-42 to 52-46 500hp) 18 knots 115 nautical miles (Total range is twice the radius of action).