THIS is is one of the most important vessels afloat with a horizontal diesel engine used for main propulsion. Horizontal prime movers were at one time an important part of marine propulsion before the development of the vertical reciprocating steam engine. The diesel engine so far has followed vertical reciprocating practice, but there are many instances in which the horizontal engine has big advantages, particularly where stability is a prime factor and weights have to be kept low.
The ship illustrated above is the Electric Star, built in 1933 by the South China Motorship Building and Repairing Works for the Star Ferry Company, Hong Kong. She is engaged on arduous work between Hong Kong and Kowloon. From the drawings it will be seen that the ship is a double-ended single-deck unit, the ends of the hull being made up of castings which are in effect a combination of stern frames and stem bars. The stem bars are flush with the fore end of the balanced rudders which operate behind or in front of the screw according to the direction in which the ship is moving. There are six bulkheads altogether so that the hull is particularly well subdivided against all possibilities of damage by collision.
The ship is a side-loading vessel from the top deck as well as from the main deck and this means that the utmost stability is needed, a characteristic which is amply given by distribution of weight in the propelling machinery. Diesel-electric propulsion is used, power being generated by a Crossley-Premier horizontally opposed diesel rated for 400-600 brake horse-power at 200-300 revolutions, coupled to a B.T.H. generator and exciter giving current to an electric propelling motor at either end. When one propeller is in operation, the other is turning at reduced speed. In addition to helping to overcome water friction this also does a certain amount of useful work.
The ship has an overall length of 116 feet, a beam of 28 feet and a depth of only 9 feet. The gross tonnage is 164. There is ample beam and the construction of the ship is such that sturdy, deep seatings for the engine are possible. The engine is a slow-running one, and this is admissible in a ship of this type, in which light weight would be a definite disadvantage. The main generator unit is in a special room separated at either end by staggered watertight, bulkheads from the propelling motors.
The generating part of the equipment is thus absolutely self-contained; here too are circulating pumps, bilge pumps, oil fuel transfer pumps and the main switchboard. The vessel attains a speed of 10 knots in service.
