Volume Three - The Pontoon Era - Notes on the longitudinal joint of the Penarth dock . . .

It is therefore not only necessary that the joint angles be drilled in pairs, but that they should be assembled and bolted together, and the Dock built round this joint. In this case, even if the joint angles did not present a flat plane, it would not matter, for the “hog” of one would fit into the like “sag” of the other, and the faces would come together.

In the present case, we have only the bottom joint angle to consider, the vertical and top joints being made by means of cover plates. It would therefore be sufficient after the joint angle has been built into and sufficiently riveted to the main portion of the Dock, to ensure that it will not again move, to lay down only the bottom plating of the extension piece which only sufficient frames to make sure that it did not sag between the supports. The different bottom plates should be well drifted together at all joints to make sure that they are laid out exactly as they will be after riveting up. Bolts are not sufficient, as they have too much play; well driven drifts tightly filling the holes must be used.

The joint angle should then be laid in position, and firmly bolted up at short intervals to the joint angle on to the main portion of the Dock. This being rigidly held to the main Dock structure will draw the other loose joint angle exactly to its shape, whatever that may be.

The holes connecting the joint angle to the bottom plating of the Dock should then be rimered out true without shifting either bottom plating or joint angle. The joint angle and bottom plating can then be dismounted, and re-erected in the position on the Pontoon deck, in which it will lie for the voyage round. The bottom plating during this re-erection, being again well drifted up, it follows that it will take exactly the same shape it had before, whilst the joint angle, when attached to it by rivets through the holes that were rimered true, must again assume exactly the same shape as it did when it was in close contact with its fellow angle on the main portion.

The Dock would be launched with the extension portion on its top deck, and would be towed round, and entered into Penarth Dock in this position

It follows, therefore, that there must be a complete watertight bulkhead on this portion of sufficient strength to withstand the sea on the voyage round. The edge of the joint angle should also be protected by some timbers, in case it should foul any solid or floating object.