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The Influence of Iron in Ship Construction: 1660 to 1830.

Peter Goodwin. IEng. MIMarE. Keeper & Curator of HMS Victory.

Today the hull of Victory is braced with considerable amount of iron work, either in the form of Robert's plate knees, various designs of breast hooks and other supportive strapping. Popular consensus is such that most of this iron work was present at the period of 1805, however closer analysis of the ship and supportive evidence suggests that this is not entirely true. What we do see on Victory is a transition in ship construction technique, albeit a preliminary countermeasure to strengthen weakened hull fabric, the form of which is merely a improvement on earlier methods.

With exception to bolts and nails and other more minor fittings, the first serious indication we have of iron being used as a substitute for timber components was circa 1670 when the naval shipwright Sir Anthony Deane, a protege of Samuel Pepys, built the 1st rate Royal James at Portsmouth. However Pepys, then Clerk of the Acts, rebuked Deane for using materials not authorized by the Navy Board. After visiting the dockyard, he wrote to Deane stating; "that you have of your own head, without precedent, as well as without the advice, or so much as the privity, of this Board or the Commissioner upon the place, presumed to lay aside the old secure practice of fastening your beams in your new ships with standards and knees, and in the room thereof taken upon you to do it iron ".1 Deane, defending the case that his 'iron dogs' were a stronger method of securing beams replied, "between you and myself, the King must build no more ships, if nothing can be invented but knees..., we having not one knee in the yard".2 The King, later seeing Deane's letter, supported his actions. Deane's allegations supported the fact that there was already a serious problem regarding a shortage of timber. In all probability this was incurred by resources being directed towards rebuilding London after the Great Fire of 1666. Unfortunately we have no knowledge on what the actual iron fittings looked like as the Royal James was burnt and sunk at the Battle of Solebay 28 May 1672. With respect that Deane referred to his fittings as 'iron dogs' hints that their design may have been similar to the simple iron clamps found on wrecks of Dutch colliers circa 1820.3 In these cases the beams were secured with iron 'U' shaped brackets that embraced the actual ship's frames, the arms being clamped to the sides of the beam. However this supposition is only theoretical, hopefully underwater archaeological survey of the Royal James wreck site may be resolve this matter.

Note: 1. Deane is renowned for his work 'Doctrine of Naval Architecture' published in 1670'.

Although there is no further mention regarding iron fittings in English ships until the introduction of the 1719 Establishment, the French had already begun experimenting with iron knees (courbes de fer) as early as 1707. These were introduced by M. Golbert then Deputy Inspector of Shipbuilding.4 To what degree French practice influenced English construction has yet to ascertained. The 1719 Establishment specifications include an annex titled. 'Dimension and Weight of Iron Standards on the Gundeck, Middle deck, Upper deck and Quarter deck of Royal Naval ships'.5 Of note this list relates to standards (inverted hanging knees) only. From the dimensions given these fittings were of considerable size: i.e. Dimensions of standards fitted on a 100 gun ship;

Extract from Adm. 170/429.
 
Gundeck. Length of the: Arm at the Sides 6 ft 7 ins (2.006 m)
Shortest Arm 5 ft 0 ins (1.524 m)
Thickness: Throat 11 ins (27.94 cm)
Next to it 6 ins (15.24 cm)
At the Ends 3 ins (7.62 cm)
No. & Size of Bolts: Arm to the Side 4 of 1.1/2 inch dia. (3.81 cm)
Beam 4 of 1.1/2 inch dia. (3.81 cm). 
Furthermore this source appears to indicate that the specification for iron work was formalized at the time two ships built to the 1706 Establishment, the Torbay (80) and Nottingham (60), were being rebuilt in 1719. Those fitted on the gundeck of the Torbay were 4 cwt and 2 qtrs (228.82 kg) in weight, those fitted on the Nottingham being 3 cwt I qtr (165.26 kg) and 2 cwt 3 qtrs (139.83 kg). The fact that iron fittings are listed in the Establishment specifications it does not infer that they were used extensively in ships. There are many reasons why application was limited, these are; quality of iron, cost, tradition, and personal interests.

At this period, most wrought iron produced was very brittle and subject to fracture. This was mainly due to the impurities introduced from coke during the smelting process. This problem was resolved by Abraham Darby II in 1750, 6 unfortunately little is known about how he applied this new technique. Much of the iron industry was still centered in the south east, Kent, Sussex, and Hampshire, primarily because these areas provided a plentiful supply of wood for smelting. Because production processes were involved, iron remained an expensive commodity for the first half of the 18th century. Costs were also high because a considerable quantity of iron was imported from Sweden and the American colonies; iron from these countries was of far better quality than English iron. However as industrial technology improved change became inevitable.

Shipbuilders, traditionally conservative in attitude, still considered timber preferable to iron and thus were often reluctant to adopt alternative materials irrespective of the advantage. With regards to personal interests, many officials connected with the government, the navy, and the mercantile trade had private involvement with the timber trade, thus it was in their interest to support their investments.

Irrespective of authorized specifications it appears that the design of iron standards and knees varied according to place of manufacture. Evidence supporting this is provided from French sources. In 1733 Blaise Gislain, under instructions from Maurepas, Minister of the Navy, visited the English dockyards of Chatham, Deptford and Woolwich to make observations of our ship construction techniques. His report clearly indicates variations in the design of iron standards; those made at Chatham and Woolwich being rather plain with a thick throat, that from Deptford being braced with a curved stay.7 Subsequently, the French improved the design and adapted iron fittings in place of timber to their ships more readily than the English. Such modifications, introduced by Duhamel Du Monceau are clearly shown in his treatise published in 1752.8 Knees illustrated in Duhamel's treatise are formed from three pieces of flat iron bar, some being a complete angle with a stay. Others have the angled corner omitted, the beam being additionally supported with a second plate fitted underneath, its vertical arm abutting the ship's side. Knees of the same fashion were being manufactured at Breast under the authority of Deslongchamps in the same year. In 1754 the English shipwright Mungo Murray translated and published Duhamel's treatise. 9 This was to be the first serious English doctrine printed since Sutherland's works of 1711 and 1717. 10 This work, together with the capture of the Invincible and the appointment of Sir Thomas Slade as Surveyor of the Navy in 1755, very much influenced English opinion in design, materials, and construction techniques.

The iron fittings illustrated in Duhamel's treatise closely resemble the iron knees found on the wreck of the Invincible (74) which foundered and sank off Spithead in 1758. Designed by M. Morineau, and launched at Rochfort in 1744, this vessel, was later captured by Anson at the Battle off Cape Finisterre in May 1747. The Invincible was built with quite a number of iron knees, some of which were boxed in with timber, a system of which predates any similar practice adopted on English ships. All of these iron knees dated from her construction 1740- 44. In size the length of the iron knees fitted on Invincible measure approximately 5 ft 5.1/2 ins (1.67 m), the metal being 4 ins (10.16 cm) wide and 1.1/2 ins. (3.81 cm) thick. 11

Iron fittings soon influenced current building trends especially with the ever increasing problem of procuring good compass timber for knees and riders, etc. towards the end of 18th century. This problem was expounded especially during the French Revolutionary and Napoleonic Wars when there was necessity to expand warship construction. Besides the improved smelting process aforesaid, other developments were happening in Britain's iron industry. In 1754 the first iron rolling mill was opened at Fareham producing stronger iron bar for bolts. Importantly, this a site not too distant from Royal Dockyard at Portsmouth.

The greatest breakthrough in technology came in 1784 when Henry Cort of Gosport patented a new method for converting pig iron into malleable wrought iron in a reverberatory furnace heated by common coal. The process involved a 'puddler' to stir the molten mass. As it was stirred the metal was decarbonized by air circulating through the furnace. The major advantage was that the iron remained separate from the coal fuel. This innovation was not entirely accredited to Cort, as similar processes had been tried previously by both the Cranage brothers at Coalbrookedale and by Peter Onions.12 After further experimentation, Cort invented a new method of making better quality iron bar and eyebolts, etc. using grooved rollers which he patented in 1783. Instead of the old process of hammering or cutting rolled plate in a slitting mill, Cort's system could produce about 15 tons of iron bar in 12 hours. 13 Stronger iron bolts were very necessary to ship construction especially with the introduction of plates knees, etc. He then went on provide stronger anchors for Naval ships. To assist his experiments old iron ballast was supplied to his foundry at Funtley near Fareham from Portsmouth Dockyard. Experiments, in the form of destructive testing, were carried out at each Royal Dockyard between items manufactured with Swedish Iron and Cort's iron. In March 1787 the results were published in a report supported by Lord Sheffield, David Hartley Esq. and Dr. Black (see Chapter 8). 14 The processes involved are superbly recorded in an extract of Hartley's letter dated 19 June 1786, enclosed within this report. The overall result proved that lower grade English iron could be converted to a malleable iron far stronger than that of better quality iron supplied from Sweden. This fact is clearly emphasized from part of the report;

EXPERIMENTS made at WOOLWICH Dock-Yard.
SWEDISH IRON  CORT's IRON
An anchor 43 cwt. 2 qrs. ]4 lb. An anchor 44 cwt. 3 qrs. 0 lb.
On the ninth of May: the arms of the two anchors were placed over the sides of two building slips which lie parallel to each other, (chocks ) and the shanks lay horizontally, with the rings opposite each other; the straps of two treble fall tackle blocks were then put through the rings of each anchor, and wood toggles run through the straps to secure them to the rings; a twofold block was likewise secured to each ring, to increase the purchase; the other two blocks were fastened to each end of the treble tackle falls; they being first reeved through two single blocks, lashed to bollard heads. To lead them to the capsterns which were manned with thirty-six men each after a very great strain
The ring of this anchor broke in three places, a piece 2-5ths of the circumference of the ring being separated from it entirely, and that piece broken again nearly off in the middle. In other respects the anchor remained in the same state as after the former trial. 
 
The ring and every other part of this anchor remained precisely in the same state as before either of the trials.
Not only had the quality of iron improved, the concept of using iron had now became more appreciable especially as production had increased rendering it a more cost effective commodity. This could not have come at a better time, as besides Sweden, and occasionally Spain, our other substantial source of iron had been supplied from the American Colonies. As result of the War of American Independence this source had been briefly interrupted. as result of the. The rules governing the export of iron from the American Colonies, introduced under the Iron Act in 1750, were along with many other factors, a contributory point of contention that initially lead us into the war'. Irrespective of our own expansion Swedish iron, timber, and other raw materials supplied from other Baltic States continued to be imported'. So necessary were these materials for our shipbuilding industry and war effort that trade had to be given considerable protection during the pending wars with France (1794- 1801 & 1803-1815).

Taking advantage of new technology, Gabriel Snodgrass, the Surveyor of the East India Company introduced an innovative system using iron knees, riders, and braces to the new EIC ships being built in the 1780s. Finding his scheme successful, he submitted his proposals before the Admiralty in 1792. From contemporary publications it appears that it was at this point that Britain took the lead over France on the extent that iron was employed in ship construction. 15 This was due to three factors: France was financially crippled after supporting the American cause; industrial development was thwarted by the revolution; and last, Cort's puddling process was not introduced in France until circa 1818. 16Though no immediate action was taken by the Admiralty at this stage, it appears that Snodgrass's ideas greatly influenced subsequent designs submitted by Robert Seppings who was later to become the Surveyor of the Navy in 1813. Iron fittings, based on the Snodgrass system, appear to have been adopted on warships circa 1795. These, introduced by the sub-surveyor Mr. Roberts, comprised a combination of wooden chocks braced with iron plate knees. 17 The advantage of such a system was that surplus short lengths of straight grained wood could be utilized without wastage, a very important issue by this period. Such a design can be seen on the Victory and the Trincomalee today. Their use however should be regarded more as a structural repair or strengthening measure fitted to existing ships rather than a formalized building practice. Besides Roberts, other similar designs were submitted though how extensively they were used is undetermined. 18 It was to be a further decade before iron knees were formally introduced by the Navy Board Order of 6th May 1805.19

By 1801, the dockyards were now using some 1400 tons of iron annually. 20 To meet this requirement Dockyard facilities had to be upgraded. In 1797, a weighbridge was constructed at Portsmouth Dockyard to ensure that incoming loads from contractors were correctly measured. Likewise all iron bar supplied was cut to expose its end grain and often further examined by heating the ends and beating the material to test tensile strength. Use of iron was not restricted to ships construction but other lesser fittings. A new Iron and Brass Foundry was built within Portsmouth Dockyard 50 yards north of the Block Mills. During expansion in 1803, a new furnace was installed for smelting iron and copper. With the Block Mills now operational, a metal mill was set up incorporating purpose built machinery designed by Brunel to produce iron pins for the blocks. This was opened in 1806. And thus, the technical infrastructure of Portsmouth Dockyard moved steadily towards the iron ship building era. A similar process was undertaken at other key Royal Dockyards. 21

Production of pig iron in England rose slowly from 17,000 tons in 1740 to 45,000 tons in 1785 - the time of Cort's innovation. After this date growth increased rapidly arising to an annual output of 700,000 tons by 1830. And within a further nine years production reached 1,700,000 tons, an increase of one hundred percent over a century. 22 This fact very much reflects the advantages gained by Cort's puddling process. aforesaid. Besides industrial expansion import restrictions caused by war also generated greater use of English iron irrespective that iron was still imported from Sweden. Obviously it was imperative to maintain open trade links with the Baltic, however these were threatened on two occasions. The first was caused by the Armed Neutrality - formed by the Baltic states of Denmark, Sweden, Prussia and Russia. This coalition was coerced by Napoleon to ensure neutral ships to ignored the British right of search. In brief this would effect Britains's trade supplies and assist trade to France and Spain. Inevitably this forced Britain to use alternative sources and now that relations with the former Colonies had improved, iron, and other necessary ship's stores such as masts, tar, and turpentine, were again being sent from what was now the United States of America. However, the northern coalition was soon broken with the defeat of the Danish at the Battle of Copenhagen by Nelson in 1801. This effectively brought Napoleon to heel and subsequently the war closed with the signing of the Treaty of Arniens in March 1802.

Peace was not to prevail, with the failure on both sides to adhere to the recent treaty the war reopened in 1803. Baltic supplies remained restricted, only 11,000 ships passing through the Sound in 1805. This figure had fallen to 6,000 by 1807 the decrease being mainly due to Napoleon's enforcement of the Continental System which banned all European trade with Britain which effective reduced the import of crucial supplies. After the destruction of the Danish fleet at Copenhagen in 1807 a potential threat and assistance to Napoleon was removed. From then onwards the import problem began to improve, and to counteract any further restrictions, the theatre of war was expanded into the Baltic with a British fleet led by Admiral Saumarez in the Victory. Saumarez himself re-opened diplomatic relations with Sweden ensuring that the export of iron and other raw materials to Britain was maintained. By 1809 the trade situation had considerably improved, and by 1812, regular supplies of raw materials, including iron were provided to the dockyards. 23 In consequence, the use of iron in ship construction and fittings increased.

During the war, the scarcity of timber had become relatively acute problem Attempts were made to use alternative woods such as fir and beech but these did not prove overly successful, and although introducing iron fittings would alleviate matters, the situation was further exasperated by the reservations raised by the Navy Board in April 1804. To quote "However eligible plans which have from time to time been suggested , the result has not always answered the expectations formed from them", and stated that the Board should , "act with caution". They advised the Admiralty that, and I quote, "previous to the adoption of any general plan which has not the authority of practice, to prove the utility proposed by it however plausible it may be in appearance"24

The fact that no formal introduction of iron was made until 1805 is supported from draughts of the Caledonia (1807), 25 and a draught showing the modifications made to the Union in 1810. 26 From this evidence it is clear that the existing iron plate knees currently seen on the Victory today, were not extant at Trafalgar but introduced during her 'great repair' of 1814. This point is wholly substantiated from Devis's painting of 'The Death of Nelson'. This well documented painting 27 clearly indicates that the gun deck beams were still supported with wooden hanging and lodging knees. In addition other fittings, now non-existent, are also shown (see Chapter 10). Unlike new ships built, iron plate knees fitted on the Victory were only placed at selected areas: Middle Gun Deck and Orlup. Those fitted on the former deck, which supported the Upper Gun Decks beams, are only found at every other beam, the remaining beams were furnished with the older system using Hanging and Lodging Knees. This point infers that the following;

  1. When refitting 1814/16, only half of the Upper Deck Beams were replaced incorporating the fitting of beam End Chucks and Plate Knees.
  2. The practice of only altering every other beam could have been undertaken to keep costs of timber and iron work to a minimum.
  3. Beam replacement complies with all those fitted under the Upper deck gunpurts thus the new method was adopted where greater strength was required to support to the ordnance.
  4. The practice of only altering every other beam could have been undertaken to ensure maintaining the line of the deck. Such measures are still carried out today when restoring the ship's frames where alternative defective frames are removed over a given span. When replaced and lined with the original frames, the remaining old frames can then be removed and new fitted and lined with the new frames previously replaced. This method ensures that the run of the hull shape is never compromised.
Notes:
  1. In short it appears that a good compromise was taken between improving strength and cost.
  2. That stated in 4 above complies with standard ship repair practice.
  3. Recent survey has shown that those beams supported using wooden knees were found be in a greater state of deterioration than those beams fitted with chocks and plate knees. This fact confirms that the latter stated are considerably newer.
The average dimension of the Iron Plate Knees fitted on the range of the Middle Gun Deck were found to be 3 ft. 4 ins (101.60 cm) long on the athwartships arm and 3 ft. 8 ins. (111.76 cm) long on the 'up and down arm'. The width of the plate arms varied. The athwartships arms measure 4 inches (10.20 cm) wide, the remaining vertical and angled arms being 3.1/2 inches (9.00 cm) wide. Metal thickness is 2 inches (5.08 cm) at the throat tapering to 3/4 inch (1.91 cm) at the extremities. Each were fastened with 11 bolts; 4 in the athwartships arm, 2 in the angled portion forming the lodging knee, 4 in the vertical arm and I in the angled arm. The entire thickness of the Plate Knee was found to be set into both the Beam and Chock, the exception being the lodging arm which are fayed and bolted to a Packing Piece. Furthermore, the athwartships arms are fashioned with two lugs about 4 inches (10.20 cm) wide and 2.1/2 inches (6.35 cm) deep. These provided an increase in metal width to permit better security in wake of bolts. This particular design, which does not exist on any other preserved vessel, is a rather unusual feature. Each plate knee is secured with 11 bolts two of which are driven through the lodging knee portion. Chock Knees in wake are checked into the underside of the beams in such a manner that a fore and aft slot was formed between the upper surface of the chock and lower face of the beam. This was made in order to fit opposed iron wedges that they can be tightened if components worked loose at sea. The slot itself is lined with a copper sleeve. 28

With regard to the beams of the Quarter Deck and Forecastle, these remain supported with standard wooden Hanging knees with some iron Lodging Knees. More odd is the fact that Middle Gun Deck beams remain supported with wooden Hanging and Lodging Knees. This implies that none of these beams were replaced since circa 1803 until restoration was undertaken between 1989 and 1994 from No.1 to 12 beam.

The iron knees wrought in wake of the Lower Gundeck beams differ slightly in design than those fitted on the Middle Gundeck inasmuch that there are no lugs and thus their manufacture is much simpler. These measure approximately 4 feet (121,9 cm) in length and depth; the vertical, horizontal and angled arms being 5 inches (12.7 cm) wide; metal thickness varies from 1.1/8 inches (2.85 cm) at the extremities, the throat being 3 inches (7.62 cm) thick. Each are secured with 11 bolts, two of which pass through the portion forming the lodging knee. As previously mentioned the thickness of metal is recessed into the adjacent woodwork of the Beam and Beam End Chock. Likewise all are furnished with opposing iron wedges within a copper lined slot. 'Rase marks' on relevant beams and chocks indicate that this work was undertaken during Victory's 1814/16 refit. The design of these iron knees correspond to those fitted on the Trincomalee frigate of 46 guns which was launched at Bombay in 1817. The fact that this ship was under construction while Victory was being extensively rebuilt confirms that by this period a common pattern of iron plate knee had been adopted to all naval ships.

As stated there is a difference in the design of the Iron Plate Knees between those fitted supporting the Lower Gundeck and those of the Upper Gundeck. This fact does suggest that each type may have been installed at different dates, the latter stated possibly being earlier in 1810. This point could be verified by the fact that the iron knees supporting the Upper Gundeck are fashioned with lugs, a feature similar to those previously introduced by Snodgrass, however further analysis is necessary before this point is fully confirmed.

When iron bracing was fitted between the heels of the counter timbers and the wing transom on Victory is at present uncertain but again certainly later than Victory 's.1800/03 refit. The square stern, which had changed little since the Tudor era, was not itself overly successful design. Later Sir Robert Seppings was to strongly criticize stern construction as seen by the content of his letter 29 submitted to Lord Melville 1 January 1822. This paper, which lists defects observed from some 62 line-of-battle ships and 80 frigates, includes the Victory herself; 30

No.1 - Ships referred to in the preceding Letter.

Rate Guns Ships Names Captains Name Date Nature of Defect.
2 98 London Griffith Dec 1795 "The stem works and strains when blowing fresh from the quarter. Find that by the ships getting aground, her stern-frame is very much broke and strained. The carlings of the lower-deck have worked out of their scores in the transom."
3 64 Asia McDougall Dec '95 "The poop works work 'very much."
" 74 Colossus Jenkins Jan '96 "Wales, topsides, stern frame and standards, work very much."
" 64 Mrica Horne Aug " "The poop and knees in the great cabin work very much at sea."
1 100 Victory Grey Sept " "I have also observed that the ship is very weak abaft; the transoms between the lower and middle-decks work exceedingly."
3 64 America Blankett Dec " "The heels of the stern-timbers almost worked out their steps."
1 100 Queen Charlotte A. S. Douglas Jan 1797 "The stern-frame works so much, it breaks the wooden ends of counters and buttock seams. The tiller transom works very much."
3 74 Cumberland Rowley ditto " "The stern-timbers work very much in their scores in the wing-transom."
" " Venerable Fairfax Sept. " "The counter-timber-heels worked out of their scores in the wing-transom."
" 64 Agamemnon Fancourt ditto " "The ship has dropped so much abaft, that the tiller traverses entirely on the helm-transom, and it is supposed that the stern-post works.
 
The gravity of the problem can be seen from the short extract above. The problem was further expounded by virtue that the stern of all two and three decked ships were constructed with open galleries which added unnecessary weight abaft the hull line. Well aware of the inherent failures of stern construction design the Admiralty and the Navy Board abolished galleries and introduced the Closed Stern 1798. This action alleviated the problem temporarily but it was to be a further two decades before Seppings revolutionized design. Following this trend the Victory was rebuilt with a Closed Stern during her 1800/03 refit. The additional iron bracing that we currently see today would not have been fitted at this stage but incorporated in 1814/16 or later. This statement is supported by the fact that analysis of the various iron straps and brackets fitted within the various after cabin areas (Captain's, Admiral's and Wardroom) reveal that all iron work is, by virtue of the gauge of metal employed, very much characteristic of the bracketing later introduced by Seppings circa 1820.31 If not fitted during in her rebuild it may well have been fitted in 1824 when Victory was being furnished out as the port admiral' s flagship. Bracing with iron was the only short term solution. Like Snodgrass, Seppings advocated using iron on a considerable scale.

Once Seppings had taken office, he could influence his innovations that would revolutionize ship construction. The use of iron plate knees with wood chocks, clearly seen in the construction of the frigate Trincomalee built in 1817, had now become standard shipbuilding technique. With timber conservation in mind, this practice was soon superseded by forging a complete iron knee in the form of a bracket without the angled stay which thereby virtually eliminated the use of the wooden chock and required only a packing piece. The design of these knees varied accordingly to their application as seen on the Unicorn frigate, built in 1824, and to reiterate, the iron bracketing employed supporting the stern timbers of the Victory. By this period iron was also being used for, Deck Hooks, Breast Hooks, and Crutches. thus giving greater support to the fore and after ends of a vessel. Their introduction eliminated the necessity to employ large pieces of compass oak previously used, the size of which had always been difficult to procure. 32 This practice was earlier used to as backing plates to strengthen breasthooks, etc. fitted in the Victory in 1814. More unusual is the plate fitted on the upper surface of the Breasthook fitted at the fore end of Victory 's Orlop Deck. Inspection confirms that this fitting complies to with Seppings designs. 33

The use of iron was to have an even more profound effect on ship construction. On the 10th March 1814, Seppings addressed his paper on a 'New Principle of Constructing His Majesty' Ships of War', before the Royal Society. 34 Using the principle of a 'five barred gate' Seppings showed that ships could be built more rigid. The current construction system, which relied entirely on the cohesion of transverse frames and beams, and longitudinal strength members and planking, was, because forces acted in two planes only, susceptible to 'hogging' and 'sagging'. In both cases, the strength of a ship's hull is compromised due to the flexing incurred: Seams would open up easily and decks move out of true; the hood ends of hull planking could be forced out of their rabbets. To compensate, the initial practice was to use wooden Breadth, Top and Middle Riders, each fitted against the ships side, spanning two deck levels. This is clearly seen on an updated draught of the 98 gun Dreadnought, 35 and evidence that Victory was so fitted is indicated in the well known Devis painting aforementioned. In short, Seppings proposed that the inherent transverse forces would be counteracted if a hull was braced with diagonal laid riders.

The principle of diagonal bracing was first , "successfully adopted in the 74 gun ship Kent in 1805". 36 Seppings later improved this design by fitting diagonal timbers between the gunports and fitting diagonal carlings between beams and laying diagonal deck planking. This became universally known as the 'trussed frame' system'. 37 This was not an entirely new innovation as diagonal riders had been used experimentally before both in France and America, though not on a wide scale. The USS Constitution of 1797 itself is a surviving example and recent reconstruction has incorporated such timbers in accord with Humphries' specifications. 39 One advantage of Seppings design was that short lengths of timber could be used thereby reducing timber wastage. Seppings also introduced a method of stiffening a hull by inserting opposed wedges in the spaces between the floor timbers thereby producing a continuous rigid form. It was now but a short step before the diagonal timber riders were substituted with those of iron. A classic example of diagonal iron bracing can be seen on the frigate 'Unicorn' now at Dundee. This vessel, built at Chatham in 1824 is the archetype of a ship encompassing Seppings innovative designs: the Round Bow, Round Stern, iron knees, riders and stanchions, and built-up solid bulwarks. The original timber crutches and breasthooks used on both the Victory and Trincomalee were now made entirely of iron giving greater strength afore and abaft The overall effect of Seppings' work was that ship length was now less restricted and in 1832 a new class of ship was introduced, these having 90 guns, mounted on two decks only as opposed to the 3 decked 90's some thirty years earlier.

Prior to this other proposals were submitted in an effort to reduce hogging. One such innovation comprised fitting 'U' shaped iron braces set between the main frames in wake of gun port sills and ledges. Whether this rather unique system was actually adopted on any particular ship as an experiment is now speculative and may have been abandoned in view that its was both complicated and expensive. 40

Higher production of cheaper and better quality iron soon lead to the construction of iron warships, the first, HMS Warrior, completed in 1860. This revolutionary step in ship development heralded the eclipse of the traditional wooden Man of War which had reigned supreme since the Tudor period. However there is an ironic conclusion, inasmuch that the concept of adopting iron with timber construction, albeit first initialized without authority by Sir Anthony Deane in 1670, was later utilized, together with Seppings principle of diagonal timbers in the design of Scott's Discovery built in 1901. This vessel, now preserved at Dundee, was purposely constructed to withstand the rigorous environment of Antarctic exploration. What is less obvious is that the introduction of iron fittings, in whatever form, based on the Seppings system instigated even greater changes: The advent of Steam Propulsion - the machinery and shafting of which required the rigid hull form.

Peter Goodwin. April 1997.

Sources:

1. Bryant. A, Samuel Pepys.'. The Years of Peril. London 1952 edn. pp49-50. See also Letter: Pepys to Deane 2 May 1670. Rawlinson MSS.
2. Ibid. p50. See also Letter.'. Deane to Pepys 5 May 1670. Rawlinson MSS.
3. Adams. J, (van Holk & Maavleveld): Dredgers & Archaeology.'. Shipfinds from the Slufier. 1990.
4. Ollivier. B, (ed. Roberts. D). Eighteenth Century Shipbuilding: Remarks on the Navies of the English and Dutch. (1737). Robertsbridge 1992. P361. NMM Adm. 170/429.
5. ADM. 170/429. Establisment Book 1719: See also Goodwin. P, The Construction and Fitting of the Sailing Man of war 1650 - 1850. London 1987. pp260 - 261.
6. Singer, Holmyard. Hall & Williams. A History of Technology: The Industrial Revolution 1750-1850. Vol. IV. Oxford 1958. p106.
7. Duhamel Du Monceau Papers. Peabody Museum, Salnem: USA.
8. Monceau, D. du. Treatise on Naval Architecture. Paris 1752. & 2nd Edn. 1758.
9. Murray. M. A Treatise on Shipbuilding and Navigation. London 1754.
10. Sutherland. W. Britains Glory or Shipbuilding Unveiled 1717. See also Sutherland. W, The Shipbuilders Assistant. 1711.
11. Details supplied from John Bingemen; Archeaologist Invincible wreck site.
12. A History of Technology: The Industrial Revolution 1750-1850. Op cit. . p106.
13. Ibid. p106-107.
14. Cort. H, A Brief State of Facts relative to The New Method of making BAR IRON With Raw Pit Coal and Grooved Roller: Discovered and Brought to Perfection by Mr. Henry Cort, of Gosport.
15. Recueil De Planches, De L 'Encyclopedic Par Orde De Matieres Tome Cinquieme. Paris 1787. Figs. 975 & 986.
16. A History of Technology: The Industrial Revolution 1750-1850. Op cit. . p115.
17. Fincham. J, A History of Naval Architecture. London 1851. p199.
18. Ibid.
19. PRO. Adm 106/2234. See also Lavery. B, Ship of the Line. Vol 1.
20. Morriss. R, The Dockvards during the Revolutionary and Napoleonic Wars Leicester 1983. p73.
21. Ibid.
22. A History of Technology: The Industrial Revolution 1750-1850. Op cit. p107
23. Morriss. R, The Dockyards during the Revolutionary and Napoleonic Wars Leicester l983. Op cit.
24. PRO. ADM. 106/2234
25. Caledonia 1807. Midship Section. 2. Box 1. ZAZ 0107. Also Caledonia 1807. Iron Knees. 46 Box 1. ZAZ. 0108
26. Union. 1810. Iron Knees. 200'. Box 4. ZAZ.0248.
27. Published by Boydell & Co. 1812.
28. Goodwin. P, Keeper & Curator's Notes. HMS Victory 1996.
29. Seppings. R: The Circular Stern of Ships of War; 1822.
30. Ibid.
31. Goodwin. P, Keeper & Curator's Notes. HMS Victory 1996.
32. Albion. The Timber Problem of the Royal Navy: 1652 -1850. SNR Pubn.
33. Mr. Seppings Tracts on the Construction of Ships. Plate X. fig. 6.
34. Seppings, R., A New Principle of Constructing His Majesty's Ships of War: 1814.
35. Dreadnought.
36. Seppings. R, Op cit. See also Lavery. B, Ship of the Line. Vol.1.
37 Seppings. R, Great Strength given to Ships of war by Application of Diagonal Braces: 1818.
38. Recueil De Planches, De L 'Encyclopedie Par Orde De Matieres. Op cit. See also, Mack. AT, The Influence of the French on English Shipbuilding in the Eighteenth Century. Flagship: Journal of the World Ship Trust. Iss. 1 Oct.1992. pp143-26.
39. Humphries. Specifications of the USS. Constitution. (Provided by Pattrick Otton).
40. Steel. D, Op cit. Plate VIII. Fig 5.

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