THE NEW CHALLENGER
Work on “Miss England 11.1.” 14/ell
THORN V C ROFTS are now well under way with Miss England III., in the quiet, efficient manner that is typical of this all-British concern.
Although all the important details of this craft are now settled, it is as yet too early to reveal some of them. For instance, the underwater construction must remain a mystery for the time being, as must the gearbox ratios and so forth. Those points that may be discussed, however, are extremely interesting. As is generally known, the hull construction is double skin, the inner planking being diagonal, while the outer is fore and aft. The propeller shafts emerge just behind the step, and are supported by cutless rubber bearings, both on emerging from the hull and at the stern brackets.
The mahogany engine bearers run the whole length of the boat, and are an integral part of the hull.
There will be only one mechanic beside the driver, the wheel being offset to starboard. The two engines will run entirely independently, with separate throttle control to keep the r.p.m. of each identical.
The cooling water scoops will be at the stern, and will be assisted by circulating pumps. Before starting the engines, water must be pumped to the cylinder jackets by hand, after which the flow is controlled by thermostat, with an additional hand control.
All the materials used are the very best it it is possible to obtain. The rudders are of hundred-ton steel, while the propellers are being machined from a solid forging.
The two 12-cylinder Rolls-Royce engines each develop 2,000 h.p. approximately, at some 3,500 r.p.m. As in the case of Miss England II., the drive is taken forward, this time to two gearboxes, and then back at an acute angle to the horizontal. One of the chief advantages of the forward drive system is that the propeller shaft can be nearly horizontal. Many people seem to think that Miss England III. is provided with two propellers to overcome torque reaction ; but this is not so. The torque reaction remains, and is a loss just the same, only in the case of a twin-screw vessel, it has no effect on the steering. The propeller speed of Miss England III. has not yet been announced, but it is fairly safe to assume that this will be considerably lower than in the case of Miss England II., probably in the
neighbourhood of 6,500 r.p.m. Although the propeller of Miss England IL turned at 12,000 r.p.m., this speed was never thought to be the most efficient, but lower revs., and a consequently large propeller, would have rendered the torque reaction too great for a single screw boat. The question to be decided is : Will they have a single screw, with a very little drag, running at a slightly inefficient speed, or will they have two propellers running at their efficient speeds, and a little extra drag ? We shall see which is the better.
The contest for the World’s water speed record will be extremely keen this year, as Oar Wood states that his new boat will be capable of 120 m.p.h., which, as every keen motorboatist knows, means that he will travel at approximately one hundred and twenty miles per hour.