HMS Victory "afloat" again on high-tech, hull-protecting supports
HMS Victory, which has been in dry dock for almost a century, is once again "afloat" – but not on the water. Instead, it is being supported by a high-tech system that prevents the 255-year-old ship from sagging under its own weight by mimicking the pressure of the sea pushing against the vessel's hull and keel.
Famous as the flagship of Lord Viscount Vice-Admiral Horatio Nelson when he defeated the combined French and Spanish fleets at the Battle of Trafalgar in 1805, HMS Victory is the world's oldest commissioned warship. However, the Royal Navy's 104-gun first-rate ship of the line has suffered from a long history of war damage, accidents, neglect, and threats of scrapping.
Since being launched in 1765, the Victory has avoided the chop many times. Even before Trafalgar, she was deemed unseaworthy and almost ended up as a hospital ship for prisoners of war before being ordered reconstructed to replace the lost HMS Impregnable in 1799.
At Trafalgar, she was so badly damaged that she had to be towed to Gibraltar before returning to England where she did duty as a storage depot ship, troopship, prison ship, tender, and floating school. Over the next century, she deteriorated badly and was once rammed and almost sunk, and it was only continuing public interest and outcry that kept the ship from being broken up.
In 1922, Victory found her permanent home in the world's oldest operational dry dock at what is now the Portsmouth Historic Dockyard at the National Museum of the Royal Navy (NMRN), where she still serves as a Navy vessel under a commanding officer. Since then, she's undergone many refits in a constant battle against old war damage, deathwatch beetles, and dry rot, resulting in tonnes of original timbers being replaced and recycled as crafted souvenirs to help pay for the restoration.
Unfortunately, saving Victory by taking her out of the water also exposed her to a more insidious enemy – gravity. Wooden ships like Victory are not designed to be out of the water. In fact, they rely on water to keep their seams tight and to support the hull with constantly changing pressures. Between sitting on 22 steel cradles since 1922 and having her outer planking replaced over the last 40 years, Victory's hull has sagged at a rate of 0.5 cm (0.2 in) per year and has shifted a full 20 cm (8 in) to date.
To prevent further damage, the Museum and BAE Systems undertook a £40-million (US$52-million) renovation project that involved removing the masts and yards, repainting the hull, and refurbishing Hardy's Cabin and the Great Cabin. In addition, 89.25 billion laser measurements were taken and used to design a new, active support system.
Instead of the steel cradles, the 3,600-tonne Victory is now supported by 134 "smart" props. These incorporate sensors that measure the pressures being placed on the hull on a minute-by-minute basis and can then adjust themselves to relieve stresses in the same way that the sea would if the ship was afloat.
In addition, the new arrangement allowed the installation of a new Under Hull Path that will allow visitors to walk under the ship's hull for the first time.
"Reaching this halfway stage, in a two-decade-long conservation project, is an extraordinary achievement," says Andrew Baines, Project Director from the NMRN. "Each prop has a load cell, so we can know, on a minute-by-minute basis, how much of HMS Victory’s weight is being carried, providing the Museum with invaluable insight into her stability and helping us to prevent damage to her structure. Before the pandemic hit we had hit a critical stage in the project, so it was fantastic that we were able to work with BAE Systems to get back up and running within social distancing restrictions so quickly."
The public will be able to view HMS Victory and its innovative support system when the Portsmouth Historic Dockyard reopens on August 24.
Source: BAE Systems