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 1988.
The Barnett-class lifeboat was designed in 1923 by James Rennie Barnett, OBE, MINA, the Consulting Naval Architect for the Institution, and was named after him. The boat was a significant development in lifeboat design, as it was the first RNLI lifeboat to have twin engines and twin screws.
Previously, every lifeboat carried a full set of sails, and even lifeboats fitted with engines had to maintain their sailing qualities. The Barnett-class was the first motor-powered lifeboat dependent solely on its engines. The engines sat in separate watertight engines rooms. Each engine was itself watertight, and would continue to run if the engine-room was flooded, with the engine entirely submerged. The air-intakes were located well above the water-line, even if the boat is waterlogged, and with the exception of the first of this type, the exhausts were carried up two funnels amidships.
The lifeboats had an open aft cockpit with a shelter ahead of it. There were fore and aft survivor cabins below deck, with seating for 24. If required, the boat could carry up to 130.
The boat adopted an idea from the Dutch Life-boat Service, and has a life-saving net fitted amidships, to assist with the recovery of survivors into the boat. Equipment included a line-throwing gun, an electric searchlight and an electric capstan, with electric lighting throughout. An oil spray was fitted in the bows, used to dampen the effects of waves around the lifeboat, and a fire-extinguishing plant, worked from the deck, could throw jets of Pyrene fluid to all vital parts of the casualty boat.
This type of lifeboat was intended only for stations where long distances may have to be covered, and where the life-boat can lie afloat. After making a tour round the British Isles, the first of the type was placed at on the River Mersey in 1923.
When it was introduced in 1923, the 60-foot Barnett-class lifeboat was the largest and fastest lifeboat operated by the RNLI. 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. As a result, only four were built.
The first Barnett-class lifeboats were long x beam, with a draught of . The boats were powered by two 80-bhp DE6 6-cylinder petrol engines, designed by the RNLI, with three built by Weyburn Engineering, and the fourth by J. Samuel White. The engines give a maximum speed of 9 knots. Maximum speed could be maintained even in very severe weather, with the lifeboat carrying sufficient petrol to travel 310 miles at full speed. The fourth, and final boat, Princess Mary (ON 715), stationed at Padstow Harbour, was long, due to a forward raked bow.
The boat had a displacement of just over 44 tons. It was divided into fourteen water-tight compartments, fitted with seventy air cases. Construction was with a skin and keel made of teak, ribs of Canadian rock-elm, and a stem and stern-post of English oak.
The boats served their stations well until the early 1950s, when they were replaced by 52-foot Barnett-class.