LOOKING AT a lifeboat when housed, perhaps the first design detail to catch the eye is the propeller and its tunnel.

Each of the twin propellers is housed in a tunnel built into the stern, the principal aims being shallow draft and protection for the propellers. Most lifeboats have tunnels. They vary in depth, depending on the class of lifeboat; their construction (seen in the photographs of a 48" 6" Oakley lifeboat below) calls for the work of an exceptionally skilled boatbuilder.

The cant, which can be seen coming from the sternpost, forms the outer edge of the tunnel. It has to be shaped in two planes, the curve running fore and aft as well as vertically; it also has to be rebated to receive the timbers of the tunnel and the boat's planking. This cant is shaped, with handsaw and adze, from two solid baulks of African mahogany scarphed together. The curved timbers of the tunnel, 2" by li" English oak, are bent to shape round a jig before being fitted to the boat. Over thetimbers will be two skins of African mahogany planking, laid diagonally at 60° to each other: the inner planking f *, the outer J". Each plank is shaped to a radiused template so that it fits exactly to the curve of the timbers, and is fastened with clenched copper nails, 3" centres.

Note the square trunks (centre of photographs) through which a tool can be used to free the propeller should it be fouled by rope or wreckage during a service. Note, too, the strips of calico laid temporarily along the joints of the deadwood (left); soaked in linseed oil, they will keep the joints tight until the time comes to paint the boat..