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Volume Three - The Pontoon Era - Proposed off-shore dock . . .

An end elevation drawing of the proposed Penarth pontoon showing connections to the quayside and the critical dimensions of the off-shore type of dock. The following letter accompanied the drawings.

"Messrs. Penarth Shipbuilding & Ship Building Co., Ltd., Penarth, Glamorganshire - Gentlemen - Proposed Off-shore Dock.

We have examined the sketches of the proposed Dock and beg to offer the following comments. We presume that this scheme is meant to be considered a finished design, (for there are many portions of the design, notably, for instance, the skin plating, and some of the framing, which have evidently not been examined), but rather as an indication of the Company's views, as to the requirements in the way of general strength, and more specifically that in the sense of the longitudinal axis of the Dock.

In our design, the continuous series of braced longitudinal framings spaced every 2'-6”, have, with the central plate bulkhead, hitherto always been formed to afford sufficient longitudinal resistance, but we should propose in the present case, which is undoubtedly a broad Dock, (although not more so than some that have already been built), to make the temporary bulkhead, which has always been allowed for in the longitudinal joint chamber, into a permanent one, the same as any other internal watertight bulkhead. In this case, we should propose also to make the new compartment or division thus formed a fresh pumping division, providing it with troughs, pipes and valves leading to the main drain. We might point out that such a bulkhead occurs in the best position for strengthening the Dock longitudinally, being the outside of the Dock, away from the great girder formed by the Wall itself, whose extra depth and stiffness would almost render redundant the resistance of a shallow pontoon girder placed anywhere near it.

The new sketches, shown as stiffened by two longitudinal keelsons of the full depth of the Pontoon. We usually put three longitudinal girders at this position, one of the full depth of the Pontoon directly under the keel, and the others one each side of the central one, each of sufficient strength to convey the maximum load that can come on them, either to the central girder, and to the transverse girders, or else directly to these latter.


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