Multi-million-pound works are under way to create a new cradle for Nelson's flagship HMS Victory to prevent it sagging under its own weight.
A total of 134 15ft adjustable steel props are being fitted at a cost of £3 million to support the 252-year-old ship in the same way as if it was sat in water.
A spokeswoman for Portsmouth Historic Dockyard explained:
"HMS Victory has been sitting in a dry dock in Portsmouth since 1922 supported by 22 steel cradles positioned six metres apart.
"It has been well documented that the 252-year-old ship is creeping under her own weight and following a detailed laser scan of 89.25 billion measurements and computer modeling, a new support system has been designed to mimic how the ship would sit in water.
"Rather than the existing steel 'blades' which are placing considerable strain on the hull structure, these will be replaced by 134 15-foot adjustable steel props fitted over two levels.
"This will completely revolutionise the support system and share the ship's 2000 tonnes load between them.
"Each prop is telescopic and features a cell monitoring the load around the clock and which is easily adjusted."
The 18-month project, being carried out by BAE Systems, follows £40 million refurbishment works which began in 2011 which have included removing the masts and yards before work to prevent water ingress and reduce rot, repainting of the ship's hull and refurbishing Hardy's Cabin and the Great Cabin.
A new walkway for visitors was also installed enabling access to more of the ship, along with a new fire detection and fire suppression system.
The National Museum of the Royal Navy (NMRN) now owns and operates the ship.
Andrew Baines, project director, said: "Over the last 40 years, all the outer planking of the ship has been replaced. The outer planks held the hull in place but, like a corset, with its strings loosened, the hull is now moving and bulging.
"The hull is moving at a rate of 0.5cm each year, so 20 centimetres over the last 40 years. This is untenable and must be remedied before irreversible damage is done.
"The new support system will cradle the ship much like she would be in water. The existing cradles will be removed in stages across the project's duration and visitors will start to notice a real change in the look of the dry dock."
Professor Dominic Tweddle, director general of the NMRN, added: "Victory is possibly the most famous ship in the world. She remains a commissioned ship and the flagship of the First Sea Lord.
"The dry dock, in which she sits, is also the oldest in the world, and this is the first time something like this has ever been done on a historic ship. So we have been really tested with this scheme.
"Our priority though is to stop the ship from moving, get her into a stable condition and then take the necessary steps to ensure the hull is here for another 250 years."
The ship, which has welcomed more than 30 million visitors since it opened to the public in 1928, will remain open in Portsmouth Historic Dockyard.