RESTORATION OF THE , 15th May 2009 Professor Bailey, of Greenwich University, said that it was realised six years ago that the Cutty Sark was decaying. Much of the ship is hidden from view, for instance behind the planking there was considerable corrosion of the iron frame. The Cutty Sark Trust has no government sponsorship, and tourists are mostly shown the ship from the outside – avoiding payment to go in. So as well as conserving the ship a new museum was wanted, featuring the Cutty Sark as the main exhibit. The Heritage Lottery fund contributed £20m with the proviso that the ship would be maintained for at least 50 years. She is now a symbol of Greenwich; and the Merchant Navy’s equivalent to HMS Victory, the Royal Navy Flagship at Portsmouth Dockyard. Unlike HMS Victory, 90% of the hull of the Cutty Sark is original. The Cutty Sark was the fastest ship of her time, a designed by an American, , working in . He lost money constructing the ship and never made another. The hull is composite: an iron frame with wood planking. HMS Warrior, also at Portsmouth, is of a similar date and also has a composite hull - she is still afloat. The , another example, was wrecked off Argentina, and is now just a rusting frame. Greenwich University was brought in to apply its mathematical and computer modelling skills. They considered how it would behave as it was dismantled, as its frame is now much weaker (due to corrosion) than when first built. Then they considered what support structure the ship should have – after sitting on its keel for fifty years (ships’ hulls are normally supported by water) there was some distortion, described as pancaking. They did their modelling to see if proposed work could be done without the hull collapsing – as Professor Bailey said “you only have one chance – if it goes wrong you lose it”. He said the work was not so much restoration as conservation. Problems: the decks were leaking (it did not help that salt used to clean the decks had been stored on them); the corroding frame was losing strength and could have failed in as little as ten years - it had chloride salts deep in the rust, dealt with by sand blasting and an electrolytic process (as on SS Great Britain at Bristol); and the planking was decayed. Then came the fire in May 2007 – the news instantly spreading from San Francisco to Tokyo. Fortunately the rigging, decks and most hull planking had already been removed; what burnt was a temporary superstructure covering the frame while its rust was treated. The remaining hull planking suffered some damage. The main worry was that the frame might have buckled – fortunately it survived, what little distortion it suffered being hammered out. Modelling Professor Bailey described the modelling as computational engineering, based on Hooke’s Law, linking stress to strain (Hooke, 1635-1703);Young’s Modulus (Young, 1773-1829); and the Poisson Ratio (Poisson, 1781-1840). Three-dimensional stress/strain analysis was started in 1950s by aircraft companies, and improved as more powerful computers came along. Computer Aided Design enabled it to be applied to real world geometries. He showed pictures of the computed result of a bird strike on the input fan of a jet engine; and of an impact on the side of a car. Supertankers have been modelled; and Viking ships in Denmark, to see how they would cope with a long journey on a lorry to a new museum. Animal bodies too, looking at the stress and strain involved in chewing. The Cutty Sark model marked the first phase of the restoration. It is based on surviving original drawings (some were lost in a fire in ), a laser scan by the Mary Rose team, a condition survey done by sonic scanning, and tensile tests of the materials (allowing for decay and corrosion). The hull shape was modelled as a series of mesh elements, for each of which stress & strain relationships were calculated. The model was validated on a mock-up of part of the hull. The first use of the model was to check the strength of the frame as planking was removed. New Museum - to be in the dry dock, under the Cutty Sark. The ship will be supported by a steel frame, the keel held by internal stretcher wires. The ship will be set higher than hitherto, the waterline roughly at ground level. Upper Deck Cutty Sark Glazed Middle Deck beams: Canopy Middle Deck original plus reinforcements Stretcher wires

Struts from Keel Museum Area Dock side Keel Support

The dock itself also needs work. Instead of the ship’s weight being along the centre of the base of the dock (for which it was designed), it will press against the sides, potentionally opening up the masonry and letting in water (the water table is above the base of the dock). This will be prevented by support from external piling. As well as tourism, the Cutty Sark is to be used for sail training by the Merchant Navy – they want to put sails up! Fortunately material porous to wind is available, and the ship model demonstrates that, with care, they can. Condition Monitoring Instruments to measure electrical resistance, stress, temperature, etc are to be fitted – some, called Canaries, ‘die’ before conditions get too bad, while Parrots mimic degradation processes. The combined probability (using theory by Bayes, 1702-61) of what the readings indicate is used to estimate the condition. These instruments are already being installed and commissioned on HMS Warrior. Cutty Sark’s speed Why was she such a fast ship – the fastest of all the ? What did Hercules Linton know? This is to be studied by applying computational fluid dynamics to the model, as done by ocean yacht designers. The Cutty Sark will be ‘raced’ against the , a ship which beat her back from Shanghai to London but only after the Cutty Sark’s rudder broke when she was 400 miles ahead.