We use cookies to enhance your experience on our website. By continuing to use our website, you are agreeing to our use of cookies. You can change your cookie settings at any time. Find out more
Sir  Robert Seppings (1767–1840), by William Bradley, 1833Sir Robert Seppings (1767–1840), by William Bradley, 1833
Seppings, Sir Robert (1767–1840), naval architect, was born at Fakenham, the fourth child of Robert Seppings and his wife, Lydia, the daughter of John Milligen, a linen draper at Harleston. His father was a cattle salesman but was not very successful and the young Robert had to work as a messenger, carrying letters on a mule. Lydia's brother John Milligen, a retired naval captain living at Plymouth and childless, adopted Robert Seppings and also two daughters of his brother Thomas. One of these girls, Charlotte, later married Robert Seppings while the other married Sir Richard Dacres.

Apprenticeship and innovation, 1782–1803

In 1782 Seppings was accepted as a personal apprentice by John Henslow, the master shipwright at Plymouth. Because of his co-ordinating role, the master shipwright may be seen as the equivalent of today's general manager, and even to be accepted as apprentice by such a man was a mark of distinction. Seppings completed his apprenticeship in 1787 and, helped by wartime expansion, rose rapidly through the ranks of shipwright, quarterman, and foreman to become assistant master shipwright at Plymouth Dock in 1797. His former master, Henslow, was now the surveyor and, aware of Seppings's merit, may quite properly have influenced the rapid rise of his former pupil.

Seppings became concerned over the time and manpower needed to lift a ship onto dock blocks for the examination of the keel area. He devised a block consisting of three wedges which could be removed in two-thirds of the time and with far fewer men. This invention was tried in the docking of the San Joseph in September 1800 and adopted at Plymouth in 1801 and was so successful that the Navy Board awarded him a bonus of £1000, a very large sum equivalent to about four years' salary, while the Royal Society of Arts awarded him its gold medal in 1803. The Navy Board estimated that this improvement saved £11,000 over three years at Plymouth alone.

Chatham, 1804–1813

Seppings was further encouraged by appointment as master shipwright at Chatham in 1804, aged thirty-seven, very young for such a senior post. In this post he set to work to devise a systematic series of changes to the structure of warships to overcome the main problems of traditional frame-built ships. These were excessive deflection in a seaway leading to early rot, shortage of long timbers, and the weakness of the bow and stern against raking gunfire. The first of these problems was the most serious and cost large sums of money in repair bills.

The unequal forces of weight and buoyancy as the ship passed through waves would cause it to bend with the planks in the side sliding over each other, so that rectangular sections of the side changed in shape to lozenges. Seppings was later to describe this behaviour as like a five-bar gate without the diagonal. This deflection in shear—known as ‘breakage’—disturbed the caulking and allowed sea water to seep in between the planks, which would rot quickly, further weakening the structure. Seppings's answer was to arrange diagonal frames on the sides of his ships, later further strengthened by packing the bottom solid with timbers, supporting the deck beams on continuous shelves rather than on individual knees, and arranging the deck planking on the diagonal. His scheme was developed and tried in stages. Some of his early ideas may have been used during the refit of the 36-gun frigate Glenmore in 1800 but details are obscure.

The Navy Board was, as usual, quick to act and in 1805 approved a limited use of Seppings's ideas for the repair of the Kent. This was further developed the following year in repairs to two other ships and the full diagonal system was first fitted to the Tremendous in 1810; in 1811 the Albion incorporated the complete system. The speed with which these changes were adopted is impressive; the navy needed every ship at sea in wartime and time in dock was severely limited but the Navy Board, and presumably the Admiralty, saw Seppings's work as so important that it was worth accepting that ships were out of service for a longer time while they were strengthened.

Measurements taken when Tremendous floated out of dock showed that the breakage with Seppings's modifications was negligible. In November 1811 John Barrow, the progressive second secretary (senior permanent civil servant), called a meeting of eminent scientists to consider Seppings's work. This meeting led to Thomas Young being asked to carry out a mathematical study of the loading and strains on a ship in a seaway. His study used fluxions (as opposed to calculus) and was almost incomprehensible but generally supported Seppings. Details of the meeting reached Napoleon a few days later and he commissioned the French mathematician Dupin to study Seppings's scheme. Dupin's analysis was both more enthusiastic and clearer than that of Young. Not for the first time—or the last—engineering design was well ahead of theoretical explanation.

Seppings presented a paper on his scheme to the Royal Society in 1814, as a result of which he was elected a fellow and later, in 1818, received their Copley medal. There was some hostility to Seppings on two grounds, the first being plagiarism. Other people had, indeed, tried diagonal stiffening but without success. Gabriel Snodgrass had been very successful in using diagonals to stiffen the ship in the transverse plane but did not expand his approach to the sides. Seppings himself said that the only external influence on his thinking was the design of the covered bridge over the Rhine at Schaffhausen. It was also alleged then, and has been alleged even recently, that Seppings's work was not ‘scientific’. This is based on a fallacious equation between mathematics and science. Seppings's logical thought progression from loading by the sea to strains and hence to the alignment of structural members was truly scientific, confirmed as it was by measurement. There also seems to have been a contemporary belief that hydrodynamics was scientific while structural design was not.

An even more convincing proof of Seppings's scheme was provided in 1817, when the old 74-gun ship Justicia was used for trials before being broken up. A paper to the Royal Society showed that the breakage on undocking, measured with and without diagonals, was reduced by about a half by the stiffeners. It is interesting that in the original scheme the diagonals were in tension while those in Justicia were in compression, and Seppings was to claim that his original method was superior. The problem with wood construction is the strength of joints, and for this reason a modern designer would probably use the diagonals in compression. However, Seppings's approach worked well. A further paper in 1820 showed how the diagonal system could be used in merchant ships. Few merchant ships seem to have been built in this style, the conspicuous exception being I. K. Brunel's Great Western: Brunel acknowledged Admiralty assistance in planning her structure.

Surveyor, 1813–1832

Seppings was rewarded for his work by appointment as surveyor in 1813, the mid-forties being a typical age for appointment to this creative post. By 1815 his system was standard practice; the 120-gun Howe was probably the first new ship designed using Seppings's fully developed scheme.

Seppings was concerned over the damage and casualties at Trafalgar during Nelson's end-on approach, as the weak beak bulkhead provided little protection from raking fire. When Namur was razed in 1805 Seppings retained the heavy bow planking up to the upper gun deck and later developed this into the round bow which also became a standard feature, providing some protection against raking fire and permitting up to twelve guns to fire ahead. His round stern was less popular, mainly on aesthetic grounds, though there were a few practical problems such as the siting of the officers' ‘heads’. He was knighted on 17 August 1819 on board the royal yacht Royal George, while under sail and with the royal standard flying. He was to receive gifts marking his achievements from the sovereigns of Russia, Denmark, and the Netherlands.

The end of the war meant that few new ships were designed and Seppings had few opportunities to demonstrate his skills as a designer. The later two-deckers of the Canopus class, such as Ganges, had Seppings's structure and are best seen as a new design. They were followed by the even bigger, 90-gun, ships of the Rodney class, which had a long and successful life. They were seen as particularly good in head seas and rolled little. Nile was fitted with engines in 1852–4 and later served as the famous training ship Conway before being destroyed by fire in 1956.

Seppings produced a modified version of his scheme using iron diagonals for frigates, as may be seen in the frigate Unicorn at Dundee. This was further developed in the 1830s by Lang and Edye for use in ships of the line. As surveyor, Seppings established a model room at the Admiralty showing developments in design; many of the models from this collection survive in the Science Museum and National Maritime Museum. Seppings was a keen supporter of the Admiralty School of Naval Architecture (established in 1811), even though his own son failed the entry examination.

It is sometimes argued that Seppings's ships were heavy, which may have been true when stiffening was added to an existing ship but should not have been the case in a new design, where the stronger ship should have been lighter. Seppings claimed that there was a considerable reduction in the number of trees required to build a ship when his methods were used, which must have equated to weight reduction. Perhaps more important, it was possible to build using shorter lengths of timber rather than the long pieces which were in short supply.

In the early post-war years there were many ‘experimental sailings’ in which ships by different designers were raced against each other; identical ships achieved very different results. Great importance was attached at the time to the results, but analysis shows that the skill of the captain, not just in sailing but also in adjusting the trim and the rigging was all important. In 1832 a joint sailing competition was held with the French, who were particularly impressed with the way that Donegal, a French-built prize, was much faster after British modifications.

One of the most successful captains in experimental sailings was Captain William Symonds, whose successes were achieved in ships of his own design. It should, however, be noted that Seppings's frigate Castor was consistently fast during the late 1830s. As a result of his political contacts Symonds was appointed as surveyor to replace Seppings in 1832, the first amateur to hold that professional post. In 1836 the University of Oxford conferred the degree of DCL on Seppings.

Achievement and death

The vast increase in the size and gun power of wooden warships in the last decades from 1815 was only possible as a result of the introduction of diagonally framed ships. In 1819 the House of Commons finance committee drew attention to the savings from the greater durability of Seppings's ships. A final compliment came at the great naval exhibition of 1891, when the gallery showing progress in naval architecture was named the Seppings Gallery.

After his retirement Seppings lived at Taunton until his death there on 25 September 1840; he was buried in St Mary's Church, Taunton, where there is a tablet to his memory in the chancel which briefly records his achievements. Lady Seppings died at Taunton in 1834. His eldest son, John Milligen Seppings, was for twenty years the inspector of shipping for the East India Company at Calcutta. Another son, Captain Edward Seppings, together with his wife and two children, was killed at Cawnpore during the Indian mutiny.

David K. Brown


DNB · T. Wright, ‘Thomas Young and Robert Seppings: science and ship construction in the early 19th century’, Royal Institution (1981), 55–71 · D. K. Brown, Before the ironclad (1990) · R. Morriss, The royal dockyards during the revolutionary and Napoleonic wars (1983) · D. K. Brown, ‘The structural improvement to wooden ships instigated by Robert Seppings’, Naval Architect (May 1979) · B. Lavery, The ship of the line, 2 vols. (1983–4)


NMM, corresp. [microfilm]


W. Bradley, oils, 1833, NMM [see illus.]