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

A further letter from Clark & Standfield to Swan, Hunter, & Wigham Richardson Ltd dated 11th January 1909 outlines the design and functional issues and suggests some solutions to the problem for consideration. I felt it worthy of inclusion verbatim:

"Dear Sirs,

We are sending you herewith some notes on another method of dealing with the extension portion of this Dock. This system avoids the necessity of making the joint before the Dock is launched, possible extra risk in towing a broad and shallow Dock, and the necessity of unmaking a joint in the mud at Cardiff. Against this, however, is to be placed the fact that an extra bulkhead will be required the whole length of the Dock. This bulkhead, of course, will not by any means be a heavy affair, as it has no great water pressure to withstand.

We might perhaps also point out that in addition to the Dock being a narrower structure, thus facilitating towing, the weight of the extension portion clamped down on the Pontoon deck will assist towards balancing the unequal weight distribution of this craft. Yours very truly . . . . . Clark & Standfield."

"Notes on the Longitudinal Joint of the Penarth Dock

Where a joint is made with a proper and complete joint chamber, any small leakage in the joint itself only affects the joint chamber, which is a small portion of the Dock. In the Penarth Dock it is not thought expedient to form a complete joint chamber for the longitudinal joint. Any leakage in the joint therefore will affect the whole area of the outer compartments, that is, half the whole Pontoon. Therefore, especial care must be exercised to see that the joint is watertight. It is an easy matter to drill joint angles in pairs, and to assure the coming together of the bolt holes, and also the coincidence of the planes of the angles, but in riveting these angles into separate structures, true adjustment is lost by means of the joint angles being unequally displaced by the drag of the rivets. For instance, the holes may coincide, but the face of the angles may be bowed, and if such bending were in opposite ways, the faces of the angles would not meet, and although the bolt might be true, they could not bring the faces together, for it would mean deforming the whole shape of the Pontoon, which would be impossible when once it was riveted up.


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