Britain’s biggest warship is now Britain’s tallest warship as HMS Queen Elizabeth reaches her maximum height with the addition of her final mast.
From the tip of the newly-installed pole mast to the keel, the gigantic carrier now stands 73 metres (239ft) tall – eclipsing Tower Bridge, Nelson’s Column and, if it were possible, a Hunt or Sandown-class minehunter turned on its end.
With a draught of just shy of ten metres (33ft) it means the aircraft carrier – due to be officially named by the Queen at Rosyth on July 4 – will tower 63 metres (206ft) above the waterline.
But at that height, she’s too tall to sail beneath either of the two iconic Forth crossings – so engineers have come up with an ingenious solution.
To allow HMS Queen Elizabeth to pass safely beneath the road and rail bridges, the pole mast is lowered until it’s almost horizontal – before being raised again once safely through.
“The mast is home to antennae for communications systems which are a pivotal part of navigation and flight safety, so a solution had to be engineered to raise the Mast once the ship has transited safely underneath,” explains Petty Officer Engineering Technician (Weapon Engineering) ‘Johno’ Johnson.
“What makes the Queen Elizabeth’s pole mast different is the engineering solution to lowering the mast – it’s what lies beneath where things get really interesting.”
On its own, the pole mast is 19 metres (62ft) tall. The lower half is home to navigational lighting, while the upper part houses numerous radio and communications antennae.
The mast sits on a steel cartridge which houses two hydraulic cylinders and a hydraulic system which lower the structure to an angle of 77˚, before raising it back in place once through.
The chance to raise/lower the mast for real will come in late 2016 when HMS Queen Elizabeth leaves Rosyth to begin her sea trials.
There are 42 days to go until the carrier is launched on July 4.
Press Release, May 22, 2014; Image: Royal Navy