How do you float a 65,000-tonne ship?
Last month saw the naming of the Royal Navy’s newest aircraft carrier, HMS Queen Elizabeth. Weighing in at 65,000 tonnes and with a flight deck measuring in at 4.5 acres, she is the largest warship ever built for the Royal Navy.
Above:
HMS Queen Elizabeth.
Courtesy MoD / Crown copyright
HMS Queen Elizabeth will provide a mobile air base for the UK’s armed forces.
She will be capable of launching, landing and maintaining aircraft 24-hours-a-day in support of war efforts and humanitarian aid and disaster relief operations. The carrier will operate worldwide with the new Joint Strike Fighter Lightning II jets and a number of types of helicopter.
Due to the size of the vessel and the importance of her role, stability is critical, especially for the taking-off and landing of aircraft. Indeed new ships and often those coming out of refit go through these tests. But how is this done?
A very accurate estimation of the ship’s weight and the particular location of the centre of gravity are required. First, the build dock in Scotland was flooded very slowly so that the carrier was floating without any brows or cables attached, and with the mooring lines slack.
Weights were then moved a predetermined distance across the flight deck and the heel angle (how much the ship tips to one side or the other) was measured using pendulums set up on board.
Through various measurements of data it was possible to establish the weight of the ship and her centre of gravity.
This information will now allow the team to manage the condition of the ship during the final stages of build. It will also inform the decision on where to deploy the final quantity of solid ballast.
The ballast system will be used on board to keep the ship stable and level during her time at sea, even through heavy seas when tonnes of seawater are transferred around the ship.
Preparing the ship for her sea trials in 2017 will continue and flight trials with the Lighting II aircraft will take place in 2018. Work on HMS Queen Elizabeth’s sister ship, HMS Prince of Wales , is also underway.
