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

Mr. T. Summers cont'd :

But, by the hydraulic system, a small and light vessel took almost as long to haul up as a large and heavy one, because of the delay by the reciprocating action of the hydraulic ram whereby one-half in time was lost, and also by the time taken up in " fleeting.” Thus if the cradle had to be moved 600 feet, and the hydraulic ram moved 10 feet, there would be 60 fleets, which, at three minutes each, would occupy three hours for “ fleeting ” only. He thought the system of steel-wire haulage for slipways possessed several important advantages over any other yet introduced, as it was much less expensive to lay down, less costly to work, more rapid in its action, and could be employed for any sized vessel.

Sir John Coode.

Sir John Coode was pleased to have his view confirmed that a repairing slip was a good thing for vessels up to about 2,000 tons, but he quite agreed that for vessels beyond that tonnage, a dry dock was in every sense preferable. The mode that had been described of laying the lower end of the platform was, in his opinion, so far as he could understand it, not a satisfactory proceeding. He knew the difficulty attending such an operation ; but he thought that to sink the platform by merely weighting it with stones, and letting it down upon a dredged bed, which had been equalised by a layer of rough rubble stone, was not a satisfactory engineering operation.

Where the rise of tide was considerable, and the means of laying the fall length of the slip in the dry existed, a repairing slip might he used with advantage for vessels of a moderate size. In his own experience, he had to lay the foundation of a slip in an excavation, which had been laid under a cofferdam and dried, and there the foundation from top to bottom was rock. The rails being laid upon a solid rock, with a thin bed of neat Portland cement intervening, the operation was most successful.

But where the range of tide was small the only thing that, in his opinion, would enable an engineer to lay a satisfactory foundation, and that would warrant a shipowner in placing a ship on it, would be to construct a dam and lay the foundation entirely in the dry. That, of course, meant a dam of considerable length ; and in an operation of that kind, the difference in expense between a repairing slip and a dry dock almost, if not entirely, vanished.