November 1947: How The Engineer reported on the world’s largest post-war liner, RMS Caronia

Engineer readers who link a thriving manufacturing sector to a healthy economy might be surprised to find an advocate of this view in the upper echelons of the Royal Family.

rms coronia
The launch of the Caronia from the Clydebank yard in 1947

That was the case in 1947 when Princess Elizabeth visited the Clydebank yard of John Brown and Co, Ltd to name the Caronia, a new Cunard-White Star liner that was, at the time,  the world’s largest post war passenger liner.


With the UK still in the grip of post-war austerity, Princess Elizabeth used the occasion to acknowledge the great skill that had gone into designing and building the ship, adding that the same ingenuity would bring the UK out of the economic doldrums.

Our reporter noted that the Caronia was the second ship of the same name to be built by John Brown for Cunard ownership, the first 20,000-ton ship being launched in 1904 from the same building berth at Clydebank.

rms caronia

Cunard’s history of transatlantic services goes back to 1847, and during the luncheon that followed the launch much was made of the association between the shipping company, the shipbuilders and owners of Clydebank shipyard.

In proposing the toast of the ship and her owners, Lord Aberconway, chairman of John Brown, referred to the dual capacity of the ship and the fact that she would carry nearly 1,000 passengers (932 to be precise) in “every modern comfort which could be applied to a ship at sea”.

According to our reporter, Mr FA Bates, chairman of the Cunard-White Star Ltd, responded and said that the Cunard company was proud of the fact that its association with John Brown and the firm which preceded it went back to 1853.

For his part, Sir Stephen Pigott, managing director of Clydebank shipyard and engine works, referred to the Cunard-White Star company as the firm’s chief customer. His firm and its pre-decessors had built for Cunard a total of about 50 ships, representing a gross tonnage of over 500,000, with machinery of 750,000hp.

Everyone involved in the Caronia had good reasons to be proud of her, not least because she’d been designed for dual use in the North Atlantic and cruising in tropical waters.

To this end, many model experiments were conducted in a testing tank at Clydebank, and the size and draught of the vessel were calculated so that the ship could enter all the ports likely to be included in a world cruise itinerary.

Before heading to the engine room, our predecessor added notes on the hull design and construction, observing: “The ship is built with a cellular double bottom, which gives a continuous watertight inner skin, from fore to after peak, with 40 watertight compartments between the inner and outer bottoms. Ten watertight bulkheads form the main watertight compartments of the ship above the double bottom.”

Notes from the tech specs showed the nine-deck, 34,000 gross tonnage Caronia to be 715ft long with a promenade deck 665ft in length, and the ability to achieve a top speed of 22 knots.

The main propelling machinery, said The Engineer, comprised a twin-screw arrangement of Parsons-geared turbines, taking steam from Yarrow water tube boilers, constructed by the shipbuilders.

The two turbine units consisted of triple expansion impulse reaction turbines, designed to be operated independently in the ahead or astern direction, wrote our predecessor. The high pressure, intermediate pressure and low-pressure turbines were grouped around a main gear wheel, the condenser being underslung from its low-pressure turbine.  At full power the high-pressure turbine was built to run at 3,686rpm and the intermediate and low-pressure turbines at 1,990rpm.

“The turbine revolutions will be reduced to the propeller speed of 140rpm in the case of the high-pressure turbines, through double reduction, double helical gearing; for the intermediate and low-pressure turbines there will be single reduction helical gearing,” The Engineer added. “The primary gears of the high-pressure pinion are of the all-addendum type, whereas the high pressure second reduction gears and the intermediate and low-pressure gears are of the deep tooth involute design. The astern turbines are incorporated in the intermediate and low-pressure turbine casings.”

The single-flow main condensers were built with a cooling surface of 16,500 sq ft, which was made up of 6,554 tubes. The main boilers could be found in one compartment and comprised six side-fired, five-drum water tube boilers fitted with super heaters and air heaters.

Steam was supplied to the main turbines at a pressure of 600lb psi and a total temperature of 800F, said The Engineer. Four of the boilers each had a generating heating surface of 8,387 sq ft, and a superheating surface of 2,945 sq ft, while the remaining two boilers had a generating surface of 5,861 sq ft and a superheating surface of 2,224 sq ft.

Caronia served Cunard for 20 years and made her last journey for the company in a voyage from New York to Southampton.