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

Mr. J .B. Redman said the value and interest of the Paper would have been considerably enhanced if the Authors had given the tonnage, also the names and dimensions of the largest vessels that had been dealt with by the ingenious systems which they had described. After carefully reading the Paper, he had been unable to arrive at a conclusion as to what was speculative, and as to hat had actually been done.

He presumed that the example given of a slipway for vessels of 300 feet length, and 2,500 tons, was intended to illustrate the system advocated by the Authors. No doubt if vessels of 4,000 or 5,000 tons (which were becoming so common) could be raised upon slipways and repaired in the same manner as in dry docks, there was manifestly the advantage of light and ventilation ; but, on the other hand, the old system of graving-docks gave a level keel, and greater facilities for shoring, as compared with slipways.

The objection to a slipway for raising vessels of great weight was met by the advocates of the system by saying, “ That is true ; but the modem iron vessel is, in the first instance, launched on crossways of a very similar character.” No doubt that was so, but the vessel, until she was launched, was in the hands of the naval constructor, and the launching of the vessel was perhaps one of the most crucial epochs of its existence, and launching from the shipwright’s ways appeared to him to be a very different operation from that of re-hauling the vessel on to terra firma up a slipway, for the sake of repairs.

The Authors bad referred to the obvious disadvantage of piling, intermixed with ground of a yielding nature; but he thought they had been lather ungrateful towards a system which had formerly been used in all naval constructions, such as docks, lock-pits, slipways, and other structures where the mass of work rested upon piles.

Although the foundations for such works, in the majority of instances where the materials were at hand, were now formed by masses of concrete made with Portland cement, which were got in at a much greater depth owing to the improved mechanical advantages of the present day, still there were situations, especially in the Colonies, where, even at present, piling must be resorted to. To put piling on one side altogether, appeared to him rather to ignore a method that had done good service in constructions of that kind.