Volume Ten - Pre-Victorian to the present day - even more aspects - The Patent for the Penarth Slipway - 1881 . . .

When it is necessary to employ the aid of divers in constructing the lower submerged portion of a slipway the work is generally carried out in the following manner. The rail-bearers are first of all framed together on land, on a continuous platform of transverse sleepers (Plate 5, Figs. 3 and 4). The rails are then fixed, and, the land end of the bearers being properly scarfed to join the last length laid from the shore, the platform is floated out as nearly as possible over the position it is intended to occupy, the bed having been previously prepared by dredging, or by sinking and leveling up a sufficient quantity of stones, or by both. Guide-piles being driven, the platform is loaded with stones and sunk, after which the ends are keyed to the shore timbers, and the stone-weights, which are permanently left, adjusted, sights being taken from time to time from the top of the way to check the correctness of the work during sinking, and before it is finally left.

◊ Slipways for Repairing Ships - Plate 5 - Figs. 5 and 6.

The rails already alluded to (Plate 5, Figs. 5 and 6) are of cast iron. The outer ones are single, about 5 inches deep and 5 inches wide, while those at the centre are double, of nearly the same sectional dimensions, and connected to each other by a plate on which is cast a strong rack of about 6 inches pitch, for receiving the holding pawls on the cradle. These pawls are introduced to prevent the cradle running down the way in the event of an accident happening to the hauling gear. In the Authors' system wings are cast on each side of the centre rail, to support and guide the hauling links, which extend nearly to the bottom of the ways. The rails must be accurately cast, and are laid on the timbers with an intervening layer of felt to ensure a good bed. The joints must be carefully made, and throughout this work it is absolutely essential to avoid all inaccuracies, as they would be certain to lead to breakages of rollers, carriages or rails, which, though not endangering the safety of the vessel, would seriously interfere with the efficient and economical working of the plant.