RNLB William and Kate Johnston (ON 682)
Class overview
Builders	J Samuel White, Cowes S. E. Saunders, Cowes Saunders-Roe, Cowes Groves & Guttridge, Cowes Rowhedge Ironworks, Rowhedge
Operators	Royal National Lifeboat Institution
Built	60 ft: 1923–1929 51 ft: 1928–1949 52 ft Mk. I: 1950–1955 52 ft Mk. II: 1957–1960
In service	1923–1987
Completed	60 ft: 4 51 ft: 13 52 ft Mk. I: 10 52 ft Mk. II: 10
Retired	37
General characteristics
Type	Motor lifeboat
Displacement	60 ft: 40–44 tons 51 ft: 27 tons 52 ft: 28 tons
Length	51–60 ft (16–18 m)
Beam	60 ft: 15 ft (4.6 m) 51 ft: 13 ft 6 in (4.11 m) 52 ft Mk. I: 13 ft 6 in (4.11 m) 52 ft Mk. II: 14 ft (4.3 m)
Installed power	60 ft:2 x 80 bhp D.E. 6-cyl. petrol 51 ft: 2 x 60 bhp Weyburn CE6 6-cyl. petrol 52 ft Mk. I: 2 x 60 bhp Ferry VE6 6-cyl. diesel 52 ft Mk. II: 2 x 72 bhp Gardner 6LW 6cyl. diesel
Propulsion	2 × pitch propellers in tunnels
Speed	9.5 knots (10.9 mph; 17.6 km/h)
Range	300 nautical miles (350 mi; 560 km)
Crew	6

The Barnett-class lifeboat consists of three types of non self-righting displacement hull lifeboats operated by the Royal National Lifeboat Institution (RNLI) from its stations around the coasts of the United Kingdom and Ireland between 1923 and 1987.

The 60 ft (18.3 m) Barnett was the first twin-engined, twin-screw RNLI lifeboat, and when introduced in 1923, the largest. Designed by RNLI naval architect James Rennie Barnett, the boats pioneered many features which were to become standard on future lifeboats. They were, however too large to be slipway launched and had to be moored afloat at a time when the RNLI preferred to keep lifeboats in boathouses and consequently, only four were built.

The boats had an open aft cockpit with a shelter ahead of it. The engines were in separate watertight engines rooms with exhaust taken up two side by side funnels amidships. There were fore and aft survivor cabins below deck. The boats were powered by two RNLI designed 80 bhp DE6 6-cylinder petrol engines, three built by Weyburn Engineering and the other by J. Samuel White. The final boat was 61 ft (18.6 m) long due to a forward raked bow. The boats served their stations well until the early fifties when they were replaced by 52 ft Barnetts.

The 60 ft Barnett was too large and heavy to be slipway launched and so the 51 ft (15.5 m) type was designed as a scaled down version which would be able to be stationed at a greater number of locations. The class is sometimes referred to as the "Stromness" after the first station to receive one.

The 51 ft Barnett had an open aft cockpit with a shelter ahead of it giving access to the engine room. Ahead of the engine room was a survivor cabin and there was a forward shelter ahead of the mast. The class was powered by two 60 bhp Weyburn CE6 6-cylinder petrol engines with a single exhaust funnel ahead of the aft shelter.

The final boat of the class, RNLB Southern Africa (ON 860), was built in 1949, fourteen years after the end of regular production, and was more akin in deck layout to the first five 46ft 9in Watson-class boats built around the same time. This boat was powered by two 60 bhp Ferry VE6 6-cylinder diesels and was in effect a prototype for a post war production run of diesel powered boats. However, it was overtaken by events as James Barnett turned to midships cockpits and the new boats emerged as the 52 ft [15.8 m] class the following year. The only other 51 ft Watson to receive diesel engines was ON 755 which was re-engined with twin Ford based 65 bhp Parsons Barracuda diesels in 1965. In 1976, ON 860 also received Barracudas while serving in the relief fleet and this boat was the final member of the class in service when retired in 1981.

• RNLI
• ON943 RNLB Claude Cecil Staniforth