Cutty Sark, 1872 by Frederick Tudgay (Photo: Cutty Sark Trust)
The UK is rich in feats of Victorian architecture and engineering, from Brunel’s graceful and elegant suspension bridge at Bristol, to the vast arches of station roofs like St Pancras, and from grand civic architecture to palatial palm houses. However, of the hundreds of clippers to be built in the early 19th century, only two remain with any degree of integrity; Cutty Sark has recently been restored, while the other, City of Adelaide is awaiting restoration.
The innovation of the Victorian engineers who designed clippers was to combine state of the art materials with a sleek hydro-dynamic hull shape that could slip through the water with least resistance. Cutty Sark’s hull was of composite construction with rock elm planks below the water line and teak above, fixed to a wrought iron framework. This composite construction gave her narrow hull far more cargo space than would have been possible with an all-timber construction, and the rigidity to support three huge masts – the tallest 152 feet. The hull was sheaved in Muntz metal, a type of brass designed primarily as an anti-fouling measure, reducing the growth of weed and barnacles.
By the time it was launched in 1869, propeller-driven steam-powered shipping was already competing with sailing craft for the global trade routes. Furthermore, the Suez Canal was completed in the same year. As the canal was unsuitable for sailing ships, it was only steamers that benefitted from the shortcut to Eastern Africa, India and the Far East. As a result this clipper belongs to the final generation of great sailing ships designed for cargo, and she was among the fastest ever to be built.
|The hull prior to lifting in March 2011, supported on steel props off the sides of the dry dock (Photo: Tim Keeler Photography)|
|The ship today with replica masts and rigging and a painstakingly conserved hull, rises from the roof of Grimshaw’s visitor centre (Photo: Jonathan Taylor)|
The term ‘clipper’, which simply means a fast ship, had previously been associated with the schooners and brigs used by the Americans to beat the British naval blockade during the War of 1812. The term was adopted to describe the fast, three-masted, narrow-hulled ships of American merchants which emerged in the 1830s and were quickly adopted by the British too. With masts as tall as a 20-storey building, each bearing a number of huge, square sails and with triangular stay sails between, clippers had the ability to carry their cargo much faster than any previous sailing ship. With good winds they could cover 250 miles a day.
Cutty Sark was commissioned by the magnate Jock Willis in the 1860s and designed by Hercules Linton of ship builders Scott and Linton at Dumbarton, Scotland. However, the firm had never built anything of this size before and went bankrupt before the hull was finished. Construction had to be completed by neighbouring shipbuilders William Denny & Brothers.
On 22nd November 1869, the ship was launched at Dumbarton, towed to Greenock for closing work on her mast and rigging, and then sailed to London where she was packed and loaded for Shanghai with barrels of alcohol. Cutty Sark set sail on the 16th of February 1870 on the first of eight voyages to carry tea from China.
Cutty Sark never lived up to her commissioner’s hopes of winning the race to bring tea back to England, but in 1883 the ship started transporting wool from Australia, and it was here that she found her forte. Her first trip from Gravesend to Newcastle NSW was completed in just 83 days. This was 25 days faster than other vessels on that route at that time. Then, in 1885 the ship, loaded with wool, made a name for herself by covering the distance from England to Sydney in 77 days, and her return voyage took just 73 days. This was the start of a ten-year reign in which every merchant would know her name. On the night of 25th July 1889 the ship overtook the steam ship Britannia doing 17 knots to the amazement of its crew. Robert Olivey, second officer on the Britannia recorded the incident in the ship’s log: ‘Sailing ship overhauled and passed us!’
By 1895 steamships were taking over every route and Cutty Sark’s owner, who was now making little profit out of her, sold the vessel to a Portuguese firm. In 1916, a year after Portugal declared war on Germany, the ship, which was now named The Ferreira, was badly damaged in heavy seas. With her masts broken, she was hauled into table bay, South Africa and re-rigged as a barquentine due to the high war-time price of masts. In this arrangement only her foremast was square-rigged while the other two were rigged fore-and-aft.
In 1922 the ship was spotted by an Englishman named Wilfred Dowman while again being repaired, and a year later he bought her for substantially more than she was worth. The vessel was brought back to Britain for restoration and she returned to her original name.
SAVING CUTTY SARK FOR THE NATION
Despite the shortage in materials caused by the first world war, Dowman did well, restoring much of the clipper’s original beauty, and he opened the vessel to the public. After his death in 1936 the ship was sold to Thames Nautical Training College in Greenhithe, Kent where she was used for training cadets.
During the second world war Cutty Sark’s masts were dismantled to reduce her visibility, leaving just the stumpy lower sections, and little maintenance was carried out. It was in this condition that the now redundant ship attracted the attention of the National Maritime Museum and, with the help of the Duke of Edinburgh, the Cutty Sark Preservation Society was formed in 1953. After some preparatory repairs the Cutty Sark was moved a new purpose-built dry dock at Greenwich. The plan was to preserve the clipper as a memorial to the Merchant Navy, including those who had lost their lives in the two world wars.
|The floor of the ’tween deck was the principal casualty of the fire in 2007 and is now laid with Douglas fir and caulked as in the past, but the ironwork survived (Photo: National Maritime Museum)|
A programme of restoration and repair followed, primarily to keep out the rain and to consolidate her surviving fabric. By this time the iron frame no longer provided the rigidity required to support her masts, the lower sections of which were of wrought iron and integral with the structure of the hull. Repairs focussed on arresting the decay of the surviving timbers and metalwork, and two of the deck houses which provided the living accommodation for the crew were completely reconstructed. However, the work did not address the fundamental problem posed by the high salt content retained in the structure, which acts as a catalyst for corrosion, and for the next 30 years the ironwork continued to deteriorate.
A survey carried out in the 1980s by Three Quays Marine Services found that the structure was dangerous. Props supporting the sides of the ship had begun to cause the hull to deform, some 60 per cent of its fastenings had failed and the surveyors concluded that there was a risk of catastrophic collapse.
THE CONSERVATION PHILOSOPHY
By definition, ‘restoration’ means to return a structure to the form it had at a particular point in the past. According to internationally recognised principles set out in the Burra Charter, this may include the removal of accretions or the reassembly of existing components without the introduction of new material. The addition of new material is termed ‘reconstruction’ by the charter, while ‘conservation’, on the other hand, means ‘all the processes of looking after a place so as to retain its cultural significance’.
Traditional boat restoration, where the vessel is to be kept sailing, generally involves a much greater degree of renewal than is associated with building restoration. Both the functionality of the boat and the safety of the crew depend on the ability of structure and fabric to withstand constant exposure to abrasion, UV radiation, often violent seas and even collisions. The least intervention possible may therefore involve the replacement of large elements of fabric.
|The raised hull after completion with information panels in the converted dry dock (Photo: National Maritime Museum)|
A bid made in 1998 to the Heritage Lottery Fund for assistance with restoration did not take full account of the ship’s new environment and its change in status. Not only was the ship no longer afloat, Cutty Sark had been a Grade I listed ‘building’ since 1973. The HLF rejected the bid but encouraged a further application that was more conservative in its approach.
The Cutty Sark Trust, as the preservation society was now known, formed a limited company to manage the work in 2000, and engineering consultancy Buro Happold was appointed to oversee the conservation and restoration aspects. In turn, a conservation steering group was set up with representatives of the trust and its professional consultants, with meetings attended by representatives of the HLF, English Heritage and Greenwich Council’s conservation officer. The programme commenced in 2002 with a programme of investigation and assessment that lasted four years.
Prime considerations were:
- to stop degradation, including corrosion promoted by chloride
- to preserve fabric from her sailing days (ie pre 1922)
- to prevent further distortion of the hull.
The Heritage Lottery Fund agreed a programme of restoration in January 2005 and contributed £11.25 million towards an estimated cost of £25 million. This included a visitor centre with a controversial glass bubble designed by Eden Project architects Grimshaw.
The programme of investigation continued following funding approval. Clinker concrete ballast in the hull was hacked out and boards were carefully removed to expose the extent of corrosion. Then, in May 2007, a fire broke out in the ’tween deck, which is the large cargo deck immediately below the top deck. It raged for several hours and initially it was feared that the ship would be lost. Fortunately by then most of the original timberwork had been taken down and stored. The main casualty was the timber flooring of the ’tween deck and some from the main deck, which were to have been reused. Some of the wrought iron of the hull was also damaged, including areas of horizontal plating which braced the frame. Although badly distorted, the wrought ironwork was found to be sound, and some areas of damage were left unstraightened to tell the story.
The need to halt deterioration of the composite hull structure proved to be one of the most difficult conservation challenges. Investigations had discovered that some timbers retained levels of sodium chloride similar to those of seawater (20,000 parts per million). As it was not feasible to remove the salt content from all the timbers, the focus was on cleaning and desalinating the ironwork, and on isolating it from its environment with the best paintwork possible.
|Section through the hull at the entrance to the ship
showing one new timber and a conserved original,
packed out to restore the shape of the hull. The bolts
were fitted into the original holes to avoid damaging
original work. Caulking was left out to enable the structure to breathe. (Photo: Jonathan Taylor)
Preliminary trials indicated that desalination could be achieved using electrolysis, with small containment tanks constructed around the metal frame. The process was originally developed for ferrous archaeological artefacts recovered from shipwrecks. In essence it involves attaching the negative terminal of a battery to the ferrous artefact (in this case the frame) and the positive terminal to a separate metal object such as titanium mesh. both are immersed in water so that the artefact becomes the cathode and the titanium mesh becomes the anode. Salt (sodium chloride) breaks down in the electrically charged solution (or ‘electrolyte’), with chloride ions drawn to the anode and sodium ions drawn to the cathode.
In the event the process proved impractical for a structure as complicated as this, as well as being expensive and time consuming, and adequate results were found to be achievable through the cleaning process alone. After the timber boards of the hull had been carefully removed, the wrought ironwork was therefore cleaned, first with a low-pressure air abrasive to remove corrosion products, and then by grit-assisted water jetting, again at low pressure. The surface was then tested for residual salts using a salt-contamination meter. If the level exceeded acceptable levels, further cleaning was carried out until a satisfactory level was reached.
The metalwork was painted immediately after cleaning to prevent further corrosion using two-pack epoxy zinc phosphate primers, two-pack epoxy micacious iron oxide intermediate coats and two-pack acrylic urethane gloss-finish top coats. Film thickness of the paint system was meticulously controlled throughout.
Original ironwork was painted white, as originally, and new steelwork which was introduced alongside to supplement the originals without altering them, was painted grey.
RAISING THE HULL
|Designed as a tea clipper, Cutty Sark was a dry ship. The reinstated lead flashings and the new composite main deck ensure that rainwater is once again excluded from the structure below (Photo: Steve Perryman, English Leadworks)|
To prevent further distortion it was essential to remove all the props and take the weight off the keel. The chosen solution was to suspend the hull, once repaired and consolidated, from a series of beams that pass though it from side to side just above her waterline. Each beam has two cables just inside the hull on either side of the ship which are fixed to the keel at the bottom – in essence forming a series of giant inverted coat hangers within the hold of the ship. Each beam is supported off the sides of the dry dock by struts.
The system raised the keel off the floor of the dry dock so that it was held in suspension, and the decision was taken to raise Cutty Sark by a further three metres, creating a large visitor facility below and enabling the sleek shape of the hull to be admired from below. However, from outside the appearance of the raised ship now surrounded by Grimshaw’s glass bubble is bizarre, and the design was derided by both the architectural press and the historic ship fraternity.
Inside the ship the new structural support does not detract from the original architecture. Much of the wrought ironwork of the hull is heavily corroded, and the use of the additional ribs has enabled the original wrought ironwork to be retained.
KEEPING OUT THE RAIN
Although the new roof over the dry dock enables the environment surrounding the hull to be controlled, the environment inside depends on keeping out the rain. In particular leaks in the deck and the drainage system had meant that salt used in frosty weather to keep the main deck safe had contributed to metalwork corrosion below. The integrity of the main deck was essential.
As the fire destroyed what little remained of the teak stored for reuse on the deck, Cutty Sark’s main deck was replaced with a modern composite material with a teak veneer. This, combined with traditional leadwork particularly in the scuppers, and repairs to the structural framework ensured its integrity.
The degree of renewal necessitated by the fire and by the loss of fabric during her latter years in service means that some parts of Cutty Sark’s fabric have been added to make sense of those elements that are historic. The rigging and masts for example are a reconstruction of her days as a clipper. Other elements have been added simply to maintain its structural integrity and to avoid further loss of fabric, or for fireproofing. The results may leave the visitor feeling a little uneasy at times, unsure exactly what is original and what isn’t. Below deck, the history is clearer. like it or not, the reconstruction and restoration work does provide an extraordinary illustration of the different philosophical and practical considerations of conservation.