Steel [?]

… it was not until the year 1810, that the placing of materials in a diagonal direction to strengthen ships, was brought to any perfection; when Mr (now Sir Robert) Seppings, introduced a plan of a diagonal framing, formed by riders, (or as they are considered, braces) and trusses. This plan was first carried into effect in his Majesty's ship Tremendous, and subsequently into all ships of the line in the British Navy; the consideration of which, and the manner of carrying it into execution, will form the subject of this work.

As all arts and sciences have their infancy, and gradually advance to maturity, so the plan, as practised upon the Tremendous was preceeded by partial introductions of the system. In the year 1800, Sir Robert Seppings, in the repair of the Glenmore of 36 guns, an old and weak frigate built of fir, laid some planks in her hold crossing the footwaling in a diagonal direction, in order that they might act as ties to strengthen the ship. The success that attended this experiment induced him to extend the system; and in 1805, when the Kent of 74 guns, a ship of large dimensions, was docked for repair at Chatham, it was found that she was in a general state of weakness, for an alteration had taken place from her original sheer, for she had arched in each half of her length, no less than 17 inches. As a partial remedy, Sir Robert placed between the bends of vertical riders already in the hold, diagonal ones, lying at an angle of 45 degrees; and abutting against them and the original riders, trusses, at the same angle in an opposite direction; this framing was found in a great measure to preserve the sheer of the ship. It will be perceived … that this was an approximation to the perfection of the plan, as practised on the Tremendous, which has been followed, with slender modifications, from the year 1810 until the present time …

If a ship, like any work of civil architecture, were always at rest, it would be easy to measure the forces that act upon the several parts, and apply the materials in such quantities, and in such directions, as should in the most effectual manner resist them. But as this is not the case, the naval architect has to provide against forces acting in all directions, by the pressure of the water, the impulse of the winds and the waves, and the momentum of the body acted upon them; from these an alteration in figure generally takes place, and ships first have a disposition first to arch (or hog as it is sometimes called) longitudinally, by curving upwards in the middle in the direction of their length. Hogging is sometimes the effect of a faulty construction, but us generally brought about by the unequal distribution of the weights placed in different sections of the body, when compared with the quantity of water displaced at those places, and from the fore and after parts of the ship being frequently left unsupported by the water during the motions of pitching. To these may be added the stres of the masts downwards, not only by their own weight and that of the rigging, sails and co., but by the pull of the shrouds, and also the pressure of the water upwards, on the those floors which lie in nearly a horizontal position …

To place the materials so as to oppose the greatest and most perfect resistance to longitudinal and transverse alterations of form is the object then of the new mode of shipbuilding. … the general principle of the new mode of shipbuilding is the substitution of the triangle for the rectangle. The beakheads in ships are discontinued, and the timbers in the bows run up to the top of their sides, which forms a round bow; a plan which had long been practised in frigates, and was proposed by Sir Robert Seppings in the year 1807, to be carried into effect of ships of the line. The suggestion arose in consequence of the great number of men who were killed or wounded on the upper deck of the Victory of 100 guns, at the Battle of Trafalgar, by the grape and other small shot passing through the thin boarding of the beakhead bulkhead, as that ship passed down in order to break the line of battle of the French fleet. This alteration not only increases the strength and safety, but conduces also to the symmetry of the ships …

The first attack of those who were inimical to this system was made by asserting that the ships would lose a considerable degree of strength by the omission of the footwaling, and therefore become dangerous at sea. This opinion was given without adverting to the considerations that, independently of the diagonal framing, a very great degree of fixedness, and consequently strength, is gained by filling in the frame … It was next asserted, that the filling in the interstices between the frame timbers, would subject the ships to premature decay; and instances were adduced which were considered analogous, viz. that the frames filled in, in wake of the channels, and that those in the fore and after bodies, where the frame timbers nearly touch, are more subject to rottenness than any other part of the ship. Those, however, who made use of these arguments, had lost sight of the well-known fact, that 'when excluded from the air, even moist wood shows but little tendency to decomposition …'

A notion has been very generally current, that the strength or rigity of a ship destroys her sailing properties, and hence it was supposed that ships built according to Sir Robert Sepping's principle would be dull sailers; facts have, however, proved that this opinion is erroneous … it is not easy to comprehend how a ship, constructed from the best principles for dividing the fluid easily, and to give the required quantity of stability, should be improved by weakness, or by a continual change of form according to the relative pressure of the wind upon the sails.

Transcribed by Lars Bruzelius

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