The need to provide motor lifeboats at stations using carriage launching had first been addressed with the 35ft Self-righting motor type of 1921. Three of these boats were built and were to all intents and purposes pulling and sailing boats with an auxiliary engine. The definitive boat for production appeared in 1929, six inches longer and with the same 8ft 10in beam as the second and third 35ft types. After the first two boats had been put on station, a crash programme of production was instituted in 1931 and twelve boats were produced that year. These gave many stations their first motor lifeboats, but experience proved that stability was lacking and from ON 763 beam was increased by 5 inches. The final two single engine boats saw further beam increases, to 9ft 6in and 9ft 10in respectively. In common with the similar but non self-righting Liverpool-class, post war production switched to twin-engined versions, but only five were built. The RNLI was increasingly switching to more stable non self-righting lifeboats and the single engine 35ft 6in Self-righting motors were replaced at most stations by Liverpool-class boats in the early 1950s after only around twenty years service. The twin-engined boats had even shorter lives, being replaced at three stations by Liverpools and at the other two by 37ft s after less than fifteen years service.
Description
The challenge of producing a motor lifeboat light enough to be manhandled for carriage launching resulted in a boat weighing around 5½ tons. The single RNLI designed, Weyburn Engineering built AE6 6-cylinder petrol engine produced 35 bhp and sat in a watertight engine room beneath pent roof access hatches ahead of an aft cockpit shelter from which the mechanic operated the engine controls. Apart from a small shelter forward the boats were open. As described above, beam was increased during production in an attempt to improve stability. After World War II, five twin engined boats were built which had a beam of 10ft and a larger shelter covering the engine room and very similar to the contemporary twin engined Liverpools. The first two of these boats were powered by two 18bhp Weyburn AE4 4-cylinder petrol engines, but the final three had 20bhp Ferry FKR3 3 cylinder diesels.
