The skeleton of a ship thus formed, built with well-seasoned timber, was left standing on the stocks “in frame” for a considerable period, sometimes for years, exposed to the open weather. On it eventually a skin of planks was fastened, secured by wood trenails split and expanded by soft-wood wedges, both internally and externally; and inside the ship, to reinforce the frames and in line with them, timbers known as “riders” were worked. On the beams the decks were laid: the orlop below the water-line level, and above it, at a height suitable for the ordnance, the main or gun deck; above that the upper deck, on the ends of which were reared the poop (sometimes a half-deck, extending from the stern to the mainmast, sometimes on that a quarter-deck, over the steerage) and the forecastle.
Such, very briefly, was the mode of ship construction. The resulting structure, when caulked and swelled by sea-water, presented a water-tight and serviceable vessel. Timber provided, for ships up to a certain size, a suitable material. It afforded strength and buoyancy, and elasticity sufficient to obviate local strains and to spread the stresses due to lading, grounding, careening, or the actions of the wind and sea. The different parts of the ship’s frame gave mutual support, and the pressure of the fluid on the exterior of the hull tended, by constraining the component parts, to preserve the vessel.[8]
But the timber-built ship possessed an inherent weakness. Metal plates or girders can be bolted or riveted together so efficiently as to leave the joints between them almost as strong as the sections of the plates or girders themselves. Not so wood beams. However skilfully they might be joined, their joints were necessarily weaker than all other sections: “it was then, and still is, impracticable to develop the full strength in end connections between wooden members.”[9] The softness of the wood was an additional source of weakness. Two beams fastened together by iron bolts might form initially a close and rigid joint; but if, under the action of alternating or racking stresses, they became loosened even in a minute degree, the tendency to become still looser increased: the wood gradually yielded under the bolt washers, the bolts no longer held rigidly, “the very fact that wood and iron were dissimilar materials tended to hasten the disintegration of the structure.” With planking a similar effect obtained. Trenails, expanded by wedges and planed off flush with the planks which they held together, had only shearing strength; if once they were loosened they had little power to prevent the planks from opening further. These weaknesses were recognised. To minimize their effects the butts of frames, decks, and side planking, were arranged so that no two neighbouring butts lay in the same line. But in spite of the most painstaking craftsmanship, the size of the wooden ship was limited by its inability to withstand a high degree of stress. As sizes increased extraordinary endeavours were made to meet the hogging and sagging strains, to prevent cambering of the hull, and to stiffen it longitudinally and circumferentially. Enormous masses of timber were worked into the internal structure in the form of riders, pillars, standards, and shores, “the whole of which had an appearance of great strength, but which in fact, from its weight and injudicious combinations, was useless, if not injurious.”[10] Which did, in fact, clog the ship and usurp the space required for stowage.