"Modern Marvels: Titanic Tech" Questions
22. Was Titanic's rudder too small to be effective?
Where rudders are concerned, bigger is not always better. It's true that the larger the rudder, the more surface area there is to generate hydrodynamic torque, but larger rudders also generate more drag and require more pressure from the steering engines to turn them effectively. British naval architects during the first part of the century appear to have preferred the unbalanced rudder for merchant ships, where the blade of the rudder is entirely aft of the stock. This places the centroid of pressure (CP) relatively far out on the blade, increasing the pressure required by the steering engines to move the rudder. The balanced rudder was used for Lusitania and Mauretania (one that places the CP on the stock by having a portion of the blade ahead of the stock), but design of the stern for those two ships was dictated by Admiralty requirements. Other factors affecting a rudder's design will be familiar to aviators...tip vortices (similar to cavitation), induced drag and stall. Another consideration was protection against grounding damage. So what was the ideal design? To quote Lovett (W.J. Lovett's Class-Book of Naval Architecture, London, 1905), "Even the highest authorities are at variance in respect to the best form of rudder." For the rudder shaped like Titanic's, White (W.H. White's Manual of Naval Architecture, London, 1900) mentioned that one major advantage of its shape was that "by tapering the rudder, the power required to put the helm over is made considerably less...these considerations would not have equal force in screw steamers where the rudder is placed abaft the screws; and then the form [of the rudder here under discussion] is to be preferred." The rudder shape accepted by the H&W architects therefore appears to have been a compromise (as most rudder designs were at that time) between weight and surface area, while taking advantage of the position of the centre screw and providing protection against potential grounding. So, was Titanic's rudder big enough? White stated that "for steamships...the extreme breadth of the rudder [is often] from one-fortieth to one-sixtieth of the length...in merchant ships much smaller rudders are used, and values as low as one-hundredth have been met with." Titanic was 850' long along the waterline, her rudder was about 15' wide at the fullest part of the blade. That made it about one-fiftyseventh of the length and therefore followed White's rule of thumb. Should a larger surface area have been utilised? The shape of an enlarged rudder not only requires more powerful steering engines, but also introduces the risk of stalling the rudder at extreme rudder angles. Again, going back to White, he cautioned that (in a given example) a "broad rudder, with an area 37 per cent. greater than the narrow one, has therefore less turning effect by about 11 per cent." There's no set standard for determining what the optimal shape for a rudder for Titanic ought to have been. Oftentimes, rudder shapes were determined by copying a shape that worked well for another ship of similar dimensions. But, given the methodology laid out in the contemporary Naval Architecture books, it appears that Titanic's rudder was of adequate design to effectively manoeuvre the ship.
23. Tell us about the engine. Size, strength. How it works. Tell us about the boilers.
Two sets of reciprocating, 4-cylinder, triple-expansion engines powered the ship. Each set of engines delivered 15000 SHP at 75 rpm. Steam entered the HP cylinder at 215 psi and was exhausted out the LP cylinder at about 9 psi. The engine bedplate weighed 195 tons, the columns 21 tons each, and each HP cylinder 50 tons. Each crankshaft weighed 118 tons. The total shaft horsepower for Titanic's propelling plant was 46,000 SHP.
Use Bill Sauder's steam flow diagram to explain the operation of the engines:
24 double-ended and 5 single-ended coal-fired boilers, for a total of 159 furnaces. They supplied steam at 215 psi to the reciprocating engines.
24. Tell us about the ship's turbine?
The low-pressure turbine of the Parsons type was designed to utilise exhaust steam at 9 psi from the reciprocating engines to rotate the rotor, which in turn drove the centre screw. In this manner, additional thrust was provided at cruising speeds without additional coal consumption. The turbine rotor was one of the most difficult assemblies to manufacture. Thousands of steel blades, all which must withstand high rotational forces, had to be precisely machined and fitted to the rotor wheels. The rotor itself was 12 feet in diameter and weighed approximately 130 tons. It delivered about 16000 SHP at 165 rpm.
25. Tell us about the ship's generating plant? What did it do? How did it work?
There were four main generating sets that output 100-volt direct current primarily for three major systems: ventilation, heating and lighting. Each set consisted of a steam-driven, three-cylinder, double-expansion engine directly coupled to a dynamo rated for 400 kW. The main generating plant was located aft of the turbine room at the tank top level. An auxiliary generating plant, consisting of two 30-kW generating sets, was located above the turbine room.
26. Tell us about the electric lights, the telephone system, the gymnasium, the elevators, and other unusual aspects.
Over 10,000 incandescent lamps illuminated the Olympic-class ships. Emergency lamps powered on dedicated circuits by the auxiliary sets were placed at intervals in all passageways, public rooms and compartments throughout the ship.
The Olympic-class ships were supplied with a telephone system that was divided into two sections: the navigating group and the internal system. The navigating group was a sound-powered point-to-point system that allowed for communication between the bridge and various docking stations, the bridge and the crow's nest, the bridge and the engine room, the engine room and the boiler rooms, and the chief engineer's cabin and the engine room. The internal system connected a number of cabins through a 50-line manually-operated switchboard. Cabins involved included some First-class staterooms, staterooms for chief crewmembers and some service rooms, to include the Marconi Room. Additional sound-powered point-to-point communication was provided between pantries and galleys.
The Magneta time system consisted of two master clocks on the bridge that electrically controlled 48 remote clocks throughout the ship. Corrected ship's time was therefore automatically displayed throughout the ship.
The refrigerating system allowed for cold storage of provisions and perishable cargo, as well as supplying cold larders in pantries, bars and water coolers throughout the ship. The refrigerating engines were located on the port side of the reciprocating engine room.
27. Specifically with the Marconi, why was this one of the most technologically significant items on the ship?
The advent of the wireless telegraph meant that ships could maintain contact with shore stations and each other. No longer would a ship disappear after leaving port, only to reappear (hopefully) at her destination. By 1912, passenger revenue another example of revenue driving technological progress made the wireless a "must have" for passenger ships, and emphasis was placed on passenger traffic accordingly. It wasn't until after the Titanic disaster that emphasis was permanently placed on the navigational importance of the technology.
Regarding Titanic's apparatus, she was the first to sail with the rotary spark discharger. As mentioned earlier, this represented an effort to refine the means by which the spark was transmitted. Before the rotary disc, the range of a transmitter was a function mainly of the brute power of the spark discharge across an air gap and the length and height of the aerial. The rotary disc contained 16 contacts that spun at a high rate of speed opposite two stationary electrodes, allowing the spark to discharge hundreds of time a second whenever the telegraph key closed the circuit. The synchronous nature of these discharges resulted in a high-density musical tone that carried farther in the atmosphere. Even though the characteristics of the aerial carried by both Olympic and Titanic were identical, Titanic's range was almost double that of Olympic's, due to Titanic's newer type of discharger.
Use my SolidWorks model as reference for CG animation of disc discharger sparking:
28. How did the plumbing work? Was there running water? Private baths? Where did the water come from?
Titanic had three different plumbing systems. Before sailing, fresh water tanks were filled with filtered drinking water. Domestic tanks (hot and cold) held clean, but not filtered, water for hand and dish washing. Sea water (hot and cold) was used for baths and toilets. The water was pumped to holding tanks on Boat Deck, where the water was then gravity fed to their outlets. Only the First Class had running water from the holding tanks in their private baths and toilets. Second Class and Third Class (family staterooms only) had reservoirs incorporated into their washstands.
29. How did shipbuilders perceive the purpose of lifeboats?
At that time, shipbuilders viewed lifeboats as a means of abandoning ship for a rescue vessel in the near distance. The ship itself was seen as its own lifeboat, the watertight bulkheads keeping the ship afloat while the small boats ferried all souls to a waiting rescue ship. It was not just blind faith in bulkhead design that fostered this attitude. The technology of the time didn't provide for a reliable means for launching a large number of lifeboats in a short amount of time. The Titanic disaster provides a good example of this. The ship actually foundered under near-ideal conditions...in a calm sea, on an even keel, over a period exceeding two hours. Even then, the crew had barely enough time to launch the 16 of her 20 lifeboats that were positioned in the davits, and even those 16 were not fully loaded. Additional lifeboats may not have proved useful in Titanic's case.
The large "gantry" davits used in Britannic were an unsatisfying attempt to improve the ship's ability to launch the number of boats required to carry every soul aboard. The answer employed today is a combination of technological improvements for both lifeboat and davit...the idea today is to reduce the number of boats needed by making them larger and more self-sufficient, and to use gimbled motorised davits to lower them.
"Titanic Tech" Questions Page 3