Back by popular demand, TTra Lifeboat brings you the definitive guide to all operational RNLI lifeboat classes - starting this issue with the all-weather lifeboats… Severn The Severn is the largest of the fleet and Is designed to lie afloat. She carries a Y class inflatable which can be launched and recovered by a lightweight framework and winch, so that rescues can take place closer to the shore. The Severn shares the same hull shape as the Trent class and also has bilge keels to protect the propellers should the lifeboat take ground.

The first Severn went on station in Harwich, Essex in October 1996.

Length: 17m (55ft 9in) Beam: 5.9m (19.3ft) Displacement: 41 tonnes Speed: 25 knots Range: 250n. miles Crew: 6 Construction: Fibre Reinforced Composite (FRO Trent The Trent class lifeboat is designed to lie afloat either at deep water moorings or at a berth. The sheerline sweeps down for ease of survivor recovery and the hull is of a 'hard chine' design.

Propellers are fully protected by substantial bilge keels, enabling her to take the ground without damage.

The first production Trent went on station at Ramsgate, Kent in 1994.

length: 14.26m (46ft 9in) Beam: 4.9m (16ft lin) Pisplacement: 27.5 tonnes Speed: 25 knots Range: 250n. miles Crew: 6 Construction: Fibre Reinforced Composite (FRO Arun The Arun class was the RNLI's first UK-designed 'fast' lifeboat. It is the RNll's most numerous allweather lifeboat and was introduced in 1971. The Arun has a prominent wheelhouse and upper steering position and carries a Y boat on top of the wheelhouse.

The last Arun was built in 1990. The earlier boats are gradually being replaced by Trent and Severn class lifeboats.

length: 16-16.55m (52ft-54ft 4in) Beam: 5.43m (17ft 9in) Displacement: 25 25-32 25 tonnes Speed: Id knots Range: 230n. miles Crew: 6 Construction: Glass Reinforced Plastic (ORP) or steel (one boat) Mersey The Mersey was the first 'fast' carriage-launched lifeboat, introduced in 1988. It was designed mainly to be launched from a carriage, but can also lie afloat or be slipway launched. Features include a slightly 'boxy' wheelhouse set well aft and a sheerline flattened towards the bow.

Propellers are fully protected by partial tunnels and substantial bilge keels.

The last Mersey was built in 1993.

length: 11.77m (38ft Tin) Beam: 4m (13ft) Displacement: 14 tonnes Speed: 16 knots Range: 140n. miles Crew: 6 Construction: Aluminium or Fibre Reinforced Composite (FRO Tyne The Tyne was the first 'fast' slipway lifeboat and was introduced in 1982. It is the RNU's main slipway lifeboat, but a number also lie afloat at moorings for specific operational reasons. At nearly 18 knots, it doubled the speed of earlier slipway boats. Features include low profile wheelhouse and separate cabin aft of upper steering position. It has a shallow conventional sheerline and flared bow above the waterline, with propellers protected by substantial bilge keels.

The last Tyne was built in 1990.

Length: 14.3m (47ft) Beam: 4.48m (14ft 8in) Displacement: approx 25.5 to 26.5 tonnes Speed: 17.6 knots Range: 240n miles Crew: 6 Construction: Steel.