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

◊ Slipways for Repairing Ships - Plate 5 - Figs. 3, 4 and 5.

The longitudinal timbers or rail-bearers, disposed as in Plate 5, Figs. 3, 4 and 5, are supported by transverse sleepers 12 inches wide by 6 inches deep, placed close together. The cluster of timbers forming the centre-ways for a slipway, such as now being considered, consist of three balks of Memel or swan pitch-pine, each 13 inches square, all with scarfed and keyed joints, while the outer bearers, which are spaced abut 25 feet apart from centre to centre, having but little weight to carry and distribute, are composed of single timbers also 13 inches square. After the first starting of the slipway slight settlements are sure to take place, but are easily compensated by wedging up the rail-bearers where required.

In order to obtain sufficient depth of water to permit vessels of the desired capacity to float over the cradle when run down, it is necessary to carry the ways a considerable distance into the water. For this reason, except in situations where from the great range of tide the construction of the lower portion can be entirely effected at low water, the employment of divers is necessary. To avoid this increased expense various proposals for shortening the slip have from time to time been made and carried out. The simplest and usual plan is to make the cradle telescopic, that is, in several divisions attached to each other by sliding lengthening-bars which permit the various sections to close up when the cradle is run down for taking on a vessel, and to open out as soon as the hauling-up commences. This arrangement is successfully adopted in several slipways worked on the Authors' system. Another plan,applicable in situations where there is sufficient range of tide, is to enclose the upper part of the slip within water-tight walls, provided at the bottom with gates, which being shut at low-tide exclude the water. This method was selected in the case of a slipway on the River Tees, also worked on the Authors' system, but the gates are not now used.