ANOTHER MILESTONE on the path of lifeboat development was passed in May this year when Frank Pen/old Marshall, the 37' Oakley stationed at St Ives, the first of her class to be fitted with radar, successfully passed righting trials and went back on station complete with this new equipment.

At the time the 37' Oakley lifeboats were being built, from the late 1950s to the early 1970s, there was no radar unit made suitable for installation on this type of boat; those available were not light enough, nor were they capable of being folded for boathouse stowage, and practically all Oakley lifeboats have been housed.

Also, the earlier boats of the class had only a limited generator capacity, sufficient for the electronic equipment of the day but possibly not so for the future. Drawing upon the experience gained in larger lifeboats, the mechanical problems involved in the fitting of high output alternators with integral diode rectification were investigated and solved, the first 37' Oakley to be fitted being the St Ives boat. When the Oakley class developed into the Rother, this improvement in power supply was carried further with larger generators and a matching battery system. Concurrently a new generation of solid state lightweight radar units had appeared on the market. The majority of these were still not suitable for the harsh environment of a lifeboat's deck but, with the co-operation of the manufacturers, two were modified for lifeboat use, the first available, the EMI Electrascan, being installed in Rother class lifeboats.

These advances meant that the problem of fitting radar to the Oakley boats could be re-examined. Both 37' classes of lifeboat have upper limits of weight (because of carriage and tractor limitation), dimensions (dictated by boathouse dimensions) and stability of the lifeboat. It was also necessary to look closely into the effect of the extra buoyancy of the radome scanner on the self-righting ability of the boat.

Careful checking of all these points showed that it was possible to fit radar retrospectively to most of the 37' Oakley lifeboats and a programme for radar fitting as well as updating of other communications equipment was drawn up. A special version of the Decca 050 radar was selected to replace the EMI unit which had gone out of production.

Frank Penfold Marshall, the St Ives boat, was selected for the first fitting as her survey was the next in the class, being undertaken at Mashford Brothers, Cremyll.

Tank tests of the watertight integrity of the radome were jointly conducted by' Decca and the Siebe Gorman laboratory at Chessington, the radome being submerged under a 12' head of water. After the small modification of adding additional fastenings to the radome flanges a radar was prepared and sent to Mashfords in time for mounting on the St Ives boat. The radome is mounted on a tabernacled tripod mast which has about twice the strength fore and aft as athwartships; should the radar be hit by a head sea it will stand, but should the boat roll over and capsize in shallow water it will fracture. The hinging aluminium pins are all undercut for shearing to avoid the possibility of damage to the engine room superstructure on which the mast is mounted.

The mast folds forward and down into the forward cockpit for boathouse stowage and can be quickly erected after the boat launches.

Since the first successful tests radar has been fitted to Clacton-on-Sea lifeboat, at Ian Browns of Rowhedge for complete survey (see page 195), and the programme is under way..