Friday, 23 December 2022

Blue Riband Engineer Props

In the 20thC the great industrial nations of the World competed to build the biggest, fastest, fabbest commercial ocean liners. It was a matter of prestige [sucks to the French!] but also practicality: fast, large ocean liners could be re-purposed as really effective as troopships. And when I say large, I mean LARGE: when RMS Queen Mary [displacement 80,000 tonnes] sliced through HMS Curacoa [displacement 4,000 tonnes] like butter on 2 October 1942, she was carrying 10,000 US squaddies for the European theatre of WWII.

The prestige aspect also counted $$$s into the exchequer because foreign-johnnies were more likely to place orders with Harland & Wolff, or Swan Hunter or John Brown if a British-built ship was in the trans-Atlantic news.

Between 1838 and 1952, 35 different steam ships held the Blue Riband an informal accolade for sustaining the fastest average speed crossing the Atlantic. 25 of these cheetahs of the seas were British; 5 DE, 3 US, 1 FR (SS Normandie), 1 IT (SS Rex). When the Sirius and Great Britain juggled the record between them in 1838, some sail packets were quicker - presumably with a fair following wind; but reliability trounced speed for people and products with a deadline to meet. Those early fastest-with-the-mostest voyages took 12 to 15 days at an average speed of 9 knots = 17 km/h. By the time ships had been superseded by jet-liners in 1952, the crossing was taking 3½ days at 35½ knots = 67km/h! Which was faster than I could drive my Yaris to work.

And the last holder of the Blue Riband - for the rest of time - was/is the SS United States. Significant technical innovations were required to wrest the accolade from RMS Queen Mary. You can let this all wash over you for 16 mins: What Made the SS United States SO Fast? The ship was designed by William Francis Gibbs for the United States Lines but the US Government upfronted about 2/3rds of the cost of the project ($50million) and had significant say in the how why what of the design and manufacture. So much for the small-government anti-socialist posturing of the time. The Feds and USN had been mightily impressed by the troop carrying capacity of the Queen Mary and Queen Elizabeth and conversion for this purpose was part of the design brief. The SS United States was never required for this purpose, although both the Korean and Vietnam wars raged during her service career. Interestingly, in view of troopship capability, the beam of SS United States [30.9m] was close to Panamax size [breadth 32.3m] while the Cunard Queens were decisively too broad [36m] to travel conveniently between Atlantic and Pacific.

Earlier, Gibbs had been closely involved in the design and construction of Liberty Ships [bloboprev].

Fire-safety was also high on the list of things to incorporate - not least because SS Normandie had caught fire (while undergoing troopship conversion in NYC in 1942), capsized and been written off. The only wood inside the new ship was the butcher's block in the galley. A mahogany grand-piano was only allowed after something similar didn't burn despite being drenched in gasoline. And asbestos sheets were used throughout; which made deconstruction 20 years later a nightmare of new understanding of that material.

One aspect of speeding through the water was to have a very shallow draft and, for stability and comfort, that required lowering the centre of gravity. The solution was to have almost all the superstructure made of aluminium. Another was raking the cut-water and making the foot-print of the vessel more spindly / pointy.

But no matter about the lines and the hydrodynamics, the ship needed to be shoved through the water by something. That turned out to be new top-secret, powerful steam turbines which operated at super-heated steam temperatures. The Queen Mary had similarly powered engines but weighed in 50% bigger at 83,000t compared to 53,000t for the United States. The engines turned 4  huge 18ft = 5.5m propellers whose design was assigned to a marine engineer called Elaine Kaplan [at a party R] The forward pair of props generated considerable turbulence which was amplified aft and this created the twin problems of cavitation and vibration. The former literally ate the manganese-bronze prop-blades and the latter really annoyed passengers. Kaplan's solution was to use two different propeller designs: forward pair with four blades; the aft with five, one of which [above L] is on show at the Mariner's Museum, Newport News, VA. Like the turbines, this novel design was top-secret, cold-war-sensitive and no below-the-waterline pictures were to be published.

The project, from post-war doodles to commissioning, lasted 7 years: the SS United States was launched in June 1951, and undertook her maiden riband-scooping voyage 53 weeks later. She had less than 20 years of commercial operation. She's a sad rust bucket now. Elaine Kaplan <tsk!> doesn't get a Wikipedia entry.

100+ more Women in Science

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