The British Challenger for the Harmsworth Motor-Boat Trophy
A 400-Horse-power Racing Craft
by Our English Correspondent
Great interest is being displayed in British motor-boat circles in this year's contest for the Harmsworth trophy, which is to be decided in Long island Sound the 1st of August, the cup having been won from France last year by the "Dixie," the representative of the Motor Boat Club of America. The British Motor Yacht Club has issued its challenge, and the first competitor, in which the greatest support for English supremacy will be centered, has already shown its speed ability in its first tests and in the Monaco races last April. The 400-horse-power Wolseley-Siddeley is England's sole representative. Two days after the American victory of last year, the Wolseley Tool and Motor Company of Birmingham placed in hand the designs for a 1908 challenger, and in order that the craft should be thoroughly tuned up for the race in America, it was decided to enter it in the European races during the spring and summer. Therefore its construction was immediately begun.
In carrying out their designs, the builders decided to depart from the usual practice in such races of constructing a mere racing shell of fine lines, narrow beam, and extremely light displacement; but inclined rather toward installing plenty of power, by means of which high speed could be secured, and toward providing a greater proportion of horse-power to displacement. An engine set developing 400 horse-power at 1,000 revolutions per minute and driving twin screws was determined upon as the most satisfactory solution of the problem, and it was estimated that this high power could be secured with a weight of 3,900 pounds, giving a displacement in racing trim of 70 hundredweight, which would give a ratio of 5.7 horse-power per hundredweight of displacement.
In view of the fact that it was intended that this craft should participate in the Monte Carlo races, the hull had to be of substantial design to withstand the severe strains arising from propulsion at high speed in the heavy swell of Monaco Bay. The hull was built in the Cowes yard of Messrs. S. E. Saunders & Co. upon their well-known system, the success of which has been conspicuous in the past in regard to speedy strong vessels of this class. It measures 39 feet 4 inches in length by 6 feet beam, and has a maximum draft at the propellers of 32 inches. Wood has been utilized exclusively in the construction of the hull, which is built up of three skins. The outer sheathing is of mahogany laid horizontally, in single pieces from stem to stern without a butt; the second layer is of special oak disposed diagonally, while the internal skin is of the same wood laid vertically, so that an unusually strong hull is secured with a minimum of weight. between each sheathing of wood waterproof silk is placed. The skins are riveted to oak timbers placed 4½ inches apart, and between these timbers the three sheaths of wood are sewn together upon the Saunders system with copper wire. The main foundation is of Oregon pine sewn in one piece from stem to stern, to which is clenched a mahogany girder similarly running from end to end and braced diagonally. The boat is decked fore and aft with the exception of the engine space and cockpit, about 15 feet in length, which is protected by a waterproof canvass hood. With regard to the water lines of the hull, these are straight for a distance of 12 feet from the perpendicular stem, with a considerable flare above the waterline to lift the bow in a seaway. As the stern is approached, a rounded and flattened effect is secured.
The motors, while following the general Wolseley practice, contain several interesting features. No attempt has been made to sacrifice strength for lightness, the latter effect only being carried out in connection with the less important details, the crank-shafts, pistons, etc., only being decreased in weight by the extensive utilization of Vickers high-tensile nickel-chrome steel. The twin-screw principle of installation was decided upon in order to secure great structural strength in the motors, considering their high power, the concentration of the weight amidships insuring complete seaworthiness, combined with the benefits accruing from entirely separate units giving duplication of driving power and balancing of propeller torque.
Each engine consists of eight cylinders cast in pairs and bolted to one crankcase. With regard to the cylinders, instead of their being cast in one piece with the water jacket, the later is of planished copper separately fitted. By this m means it was rendered possible to obtain access to the inside of the jacket after the castings had been made. The copper jacket is screwed to the cast-iron cylinder casting. This arrangement has many advantages, since it is always possible to examine the internal surfaces of the cylinder wall circulation space, and so forth. Special attention has been devoted to the provision of ample water-cooling space around the valve pockets. The valves are mechanically operated, and are placed side by side along the front of the engine, the vaporizer being the only part of the mechanism carried on the rear side.
The water circulation is of the most complete description, so as to obviate the possibility of breakdown through any failure in this direction. The water is forced through the circulation system by means of power centrifugal pumps, two to each engine, driven from a universally-jointed shaft connected with the gear on the forward end of the motors, the supply being obtained through suctions placed abaft the motor. The vaporizer is fixed high up on the outside of the engine, the gas feed being through large-diameter pipes to the various inlet valves. The ignition is both high-tension electric with accumulator and coil and high-tension magneto, the engine being started up on the former (which ia also used as a stand-by) and then switched on to the latter. Lubrication is of automatic type, oil being supplied at a temperature not exceeding 110 deg. Fahr. to all the important bearings at a pressure of 12 pounds per square inch. The clutches are of the cone type in conjunction with a positive locking arrangement. Hoffman ball bearings carried in gun-metal boxes held by trunions are used for the thrust bearings, and are mounted on the same shafts as the clutches.
Owing to the distance between the crankshafts of the pair of motors being governed by the beam of the boat, and all valves, etc., being placed on the inside face of the motors, in order to permit entrance between the engines when installed, for access to those parts, the engines are set at a slight angle from the vertical. in this way the engineers will have sufficient space to attend to the working parts on either side. The angle at which the engines and propeller shafts are set is 11 deg. from the horizontal. The shafting itself is fashioned from Vickers axle carbon steel of 1 11/16-inch diameter.
The engine in running condition each weigh 1,670 pounds, and have each developed more than 207 brake horse-power at the normal running speed of 1,000 revolutions per minute. The machinery complete weighs 4,200 pounds. It is generally conceded that this challenger will prove both seaworthy and speedy, and unlike the conventional craft of this type, it is not a mere shell, but will withstand severe buffeting in heavy seas.
The performances of this boat at Monaco showed well the staunchness of the hull. The lines of the hull are such, however, that its spray-throwing qualities are not so great as those of some of the French racers, such as the new Panhard- Levassor, for example. in the mile and kilometer trials at Monaco the Wolseley-Siddeley and Panhard-Levassor boats were both evenly matched. The mile trials were made from a standing start, and the two boats tied in the final, each covering the distance in 2 minutes 1 1/5 seconds. The latter boat made the faster time in the flying kilometer test, as it covered the distance in 1 minute 3 4/5 seconds, at the rate of 35.6 miles an hour. The Wolseley-Siddeley covered this distance in 1` minute 4 2/5 seconds, which was at the rate of 34.71 miles an hour. In the longer race at Monaco, the Wolseley-Siddeley covered 31.05 miles in 54 minutes and 57 seconds, or at the rate of 33.87 miles an hour. The 124.3-miles "championship of the sea" race was won by the Panhard-Levassor in 3 hours, 46 minutes, and 2 seconds, at average speed of 32.97 miles an hour.
Up to the present time there have been no entries of American boats for the race for the Harmsworth trophy to be held in Long Island Sound on August 1. If more than three boats are entered, elimination trials will be held on July 10 and 11. This event will be the first international motor boat race of importance to be held in America, and it should do much toward stimulating the sport. The Wolseley-Siddeley racer has been entered by her present owner, The Duke of Westminster.
Transcribed from Scientific American, June 13, 1908, p. 431.
[Thanks to Greg Calkins for help in preparing this page. — LF]