The development of the racing hydroplane has been so rapid that speeds have been increased from 60 miles an hour to 130 miles an hour during the last twenty years. In September 1937 Sir Malcolm Campbell regained the record for Great Britain with his Rolls-Royce engined “Blue Bird”
SIR MALCOLM CAMPBELL AT THE WHEEL of his hydroplane, Blue Bird, during preliminary trials on Loch Lomond, Scotland. Blue Bird was only 23 feet long on the waterline, and had a beam of 9 ft 6-in. Although various light metals were used in her construction, she was built mainly of wood, and in full trim weighed only 45 cwt.
THE evolution of Blue Bird, the racing hydroplane with which Sir Malcolm Campbell broke the world’s water speed record in September 1937, was dependent to a great extent upon the behaviour of the other Blue Bird, that famous car which gained the world’s land speed record for Great Britain in 1935. The story of the land speed record, told in the chapter beginning on page 194, was inevitably linked up with the development of the internal combustion engine.
The development of the racing motor boat has also been dependent upon that of the internal combustion engine. In fewer than fifty years the motor boat has developed from a slowly-moving launch into a hydroplane capable of travelling at more than two miles a minute. The increases in speed during the last decade, however, have not been so spectacular as those achieved in connexion with the land speed record. Sir John Thornycroft took out patents in 1877 for a craft intended to skim over instead of ploughing its way through the water. This craft was the first hydroplane, but the absence of a light high-power engine held up development for many years. By 1907, however, hydroplanes were demonstrating their capabilities on both sides of the Atlantic, and in 1913 speeds of more than 50 knots had been attained.
The war of 1914-18 held up development, and in 1920 the record stood at 56 knots. This speed was reached by Commodore Gar Wood in his boat Miss America I, which was powered by engines of more than 800 horse-power. After this, power and speed increased at a remarkable rate, and many splendid craft were produced by engineers in Great Britain and in the United States. The Americans always endeavoured to pack as large an engine as possible into a boat of limited size, but the British designers aimed at a reduction of weight, which they achieved by limiting the size of the engine and of the boat. These two methods of attacking the problem have been continually matched against each other. Commodore Gar Wood replied effectively to every challenge with one of his wonderful series of Miss America boats until, in September 1937, Sir Malcolm Campbell regained the record for Great Britain with his Blue Bird. This was a triumph for the British designer, for Gar Wood’s boat Miss America X, which gained the record for America in October 1932, was powered by four supercharged engines giving a total of 6,400 brake-horse-power, whereas Blue Bird used a single Rolls-Royce engine with a brake horse-power of 2,150.
Gar Wood was the first man to achieve a speed of more than two miles a minute on water. On October 20, 1932, he recorded a speed of 124·86 miles an hour at Miami, Florida, with Miss America X. This record, remained unbroken until September 1, 1937, when Sir Malcolm Campbell, with Blue Bird, attained the speed of 126·32 miles an hour at Locarno, Switzerland, on Lake Maggiore. On the following day Blue Bird was taken out again, and the figure recorded was 129·50 miles an hour.
For many years before 1935 Sir Malcolm’s friends had been suggesting that he should build a boat with which he could attack Gar Wood’s record. In 1931, however, Campbell had made up his mind that he would be the first man to achieve a speed of 300 miles an hour on land. So determined was he to reach that goal that he would not consider the question of building a boat, and he put the idea on one side.
Once the land speed record had been raised to 300 miles an hour, Campbell promised to give up further attempts on land and turned his attention to the water. There had been a keen international struggle for the water speed record between 1930 and 1932, the contestants being the late Sir Henry Segrave, Kaye Don and the redoubtable Gar Wood. The water speed record changed hands no fewer than eight times between June 13, 1930, and October 20, 1932. After that, however, Gar Wood held the honours for nearly five years. Sir Malcolm Campbell decided to build a boat at the end of 1935. The engines that were available for his use were the two supercharged Napier Lion 1,450 horse-power engines that had been used in his record-breaking car in 1931 and 1932, and the 2,350 horse-power Rolls-Royce engine with which the 1935 record was achieved.
This particular engine was capable of delivering some 2,750 horse-power in a racing aeroplane and some 2,450 horse-power in a racing car. In a boat travelling at 120 miles an hour, however, the power output was not expected to exceed about 2,000 horse-power.
Favourable Power-Weight Ratio
THE reason for this is that the high speeds attained by aeroplanes and racing cars produced a “forced induction” effect. The fact that wind resistance increases with the square of the speed makes it easy to understand how marked this effect can be.
The problem, therefore, was to choose between a boat using the two Napier engines developing, roughly, 2,900 brake horse-power and one using the Rolls-Royce engine developing approximately 2,000 to 2,150 horse-power. Had the two Napier Lions been used, it would have been necessary to use two propellers and two gear boxes. This would have entailed extra weight,
and the drag set up by two propellers would have involved other problems of design. It was decided, therefore, to build a light boat and to use a single screw.
The work was put in the hands of Mr. Fred Cooper, M.I.N.A., the designer, and Saunders-Roe, Ltd, who built Sir Henry Segrave’s boat, Miss England II. Mr. Reid Railton, designer of the 1935 Blue Bird car, was responsible for the installation of the engine. This team of workers produced a boat which was only 23 feet long on the waterline and had a beam of 9 ft 6 in. Gar Wood’s boat was 38 ft 9 in long and had a beam of 10 feet. The power-weight ratio obtained with Blue Bird was much more favourable than that of the American boat, for Blue Bird weighed only 45 cwt - less than one-third of the weight of Miss America X.
The engine alone turned the scale at more than 15 cwt, and the gearbox, shafting and the like added a considerable amount to this figure. The hull itself was therefore extremely light, and it was in the design of the hull that the engineers and builders found such scope for their ingenuity. Sir Malcolm had at his disposal an experimental tank in which quite large models could be run at speeds equivalent to 130 miles an hour. Several weeks were spent on tank tests, and twenty-two different model forms were tried out.
THE RECORD-BREAKING HYDROPLANE Blue Bird on her special slipway. The illustration shows Sir Malcolm Campbell being helped into his life-jacket; in the foreground two men are carrying a compressed air bottle of the type used for starting the Blue Bird's engine during tests. Normally the engine was started by a Bristol gas starter unit, but when it had been warmed up and plugs had been changed, starting was carried out from an air-bottle carried on board.
When it is realized that Blue Bird was not much longer than a big dinghy, and that she had to carry an engine weighing 1,700 lb, it will be appreciated that the problem of building an immensely strong hull without adding a pound of unnecessary weight was by no means easy to solve. Eventually it was decided that the boat should be built mainly of wood, light metals -“Duralumin” and “Alclad” - being used where necessary.
Seven-ply wood was used for the bottom of the boat, and two-ply wood for the sides. The forward planing surface was metal sheathed, and the engine, mounted aft of amidships, was supported on box girders which ran right forward to support the gearbox. These girders supplied nearly all the longitudinal strength, and they were built up and boxed in with two panels of three-ply. The deck was built of six skins, giving a total thickness of only three millimetres - less than ⅛-in.
The streamlined fairing for the pilot and for the engine was carried out in spruce, doped aeroplane fabric and aluminium. The aluminium was used on the underside of the fairing, which was in contact with the water when the boat was at rest. It was impossible to insure Blue Bird, and as she was to run in water more than 600 feet deep it was decided to increase her buoyancy by stowing 36,000 table tennis balls in the bows. These balls were stowed away in forty-eight pillowcases and weighed 160 lb, but they were equivalent to one ton of buoyancy.
THE gearbox, which was of extremely light design, had a ratio of just over 2:1, and at the full engine speed the propeller was turning at nearly 9,000 revolutions a minute. As the boat was built expressly for sprints over the measured mile, it was decided that oil and water coolers in their usual forms could be dispensed with. A special thermostatically-controlled water-cooling system was designed, a water-scoop being arranged just above the propeller. The scheme was a complete innovation in hydroplane design, but worked well after certain minor modifications had been made.
The starting mechanism was operated by compressed air, and sufficient air was carried for several starts to be made, once the engine had been warmed up. Normally a dog clutch, integral with the gearbox, was disengaged, and the engine started up by a Bristol gas starter unit. After the engine had been warmed up and the special “hard” plugs had been inserted, the boat was cast off, the dog clutch engaged and the engine started up from the compressed-air bottle carried in the boat.
All the transmission gear was built of steel with a tensile strength of 120 tons, and the propeller, rudder and bracket were shaped from the solid metal. The propeller, which had to run at such a tremendous speed, was two-bladed and machined from a solid billet of high-tensile steel. It was balanced statically and dynamically with extreme care. One surprising problem with which the designers had to contend was the loss of “temper” of the propeller, because of the heating effect of its high speed in the water.
In her general appearance Blue Bird followed essentially modern European lines, with the low freeboard and the streamlined fairing for the pilot and engine. Aft of the engine was a tail, a wooden frame covered with doped fabric. During the record-breaking runs, however, this tail was removed, as modifications to the water system made it expedient to discharge the water over the transom.
A FAST RUN ON LAKE MAGGIORE, on the smooth surface of which Blue Bird eventually attained a speed of 130·43 miles an hour. The above illustration shows the boat with her streamlined tail in position; this tail was removed during the record run, as it was necessary to modify the water-cooling system and to discharge the water at the stern of the boat.
The hull of the boat was beautifully finished in the shade of blue which Sir Malcolm Campbell has always used for his racing cars. The cockpit was fitted up to give as high a degree of comfort for the pilot as could reasonably be expected in a craft of this kind. The builders installed a sprung steering wheel similar to those used in racing and sports cars, and the seat was fitted with pneumatic upholstery and was slung on brackets equipped with shock absorbers. A neat facia-board with all the necessary instruments faced the pilot, and a fire extinguisher was close to hand for use in possible emergencies. Fortunately for all concerned it was not necessary to use this extinguisher.
Blue Bird was far smaller for her power than any hydroplane previously built, and the owner and designer were confident that she would be faster than the boats of the Miss England and Miss Britain series, which were designed as compromises, as they were intended for Harmsworth Trophy racing as well as for record breaking.
The early trials were made on Loch Lomond, Scotland. Although no extremely high speeds were achieved, it was obvious that the boat was capable of travelling at speeds of about 130 miles an hour in favourable conditions.
In August 1937 Blue Bird was taken to Lake Maggiore, which, for various reasons, appeared to be the most favourable stretch of water within easy reach. Perfectly smooth water and a complete absence of wind were absolutely essential for high-speed work with such a light boat as Blue Bird, and a stretch of some three miles was necessary.
After the trials on Loch Lomond an air fin was made, for fitting over the streamlined tail. The purpose of this fin was to give additional directional stability. Neither the tail nor the fin was used, however, after it had been found necessary to modify the water-cooling system.
World’s Record on Water
On September 1 conditions were ideal and Blue Bird was taken out at 8.30 am. The engine was warmed up for ten minutes and then Sir Malcolm Campbell started on the official trial. All hopes for the success of the boat were immediately justified, her speed on the first run being 125 miles an hour and on the second 127·66 miles an hour. These speeds gave a mean of 126·32 miles an hour - just a sufficient margin over Gar Wood’s 124·86 miles an hour to assure Campbell of the world record.
It was not generally known that the attempt on the record was being made, and it was thought that Blue Bird was being given a trial run. The original engine had been slightly damaged during trials because of trouble with the circulating water system, but the modified system worked perfectly with a second engine.
Sir Malcolm was certain that a higher speed could be achieved, and he took Blue Bird out again on September 2 at 8.40 am. Once more perfect conditions of weather and water prevailed, and the first run was completed in 27·6 seconds, at a speed of 130·43 miles an hour. The second run was not quite so fast. The time was 28 seconds and the speed 128·57 miles an hour. The mean speed was 129·50 miles an hour, and this satisfied Sir Malcolm and his team of workers.
It was obvious that there was a good reserve in hand and that the boat was capable of even higher speeds, but Sir Malcolm expressed the opinion that there was still much to learn about the operation of boats at such high speeds. He found that steering the boat at full speed was far more difficult than steering Blue Bird, his record-breaking car, at 300 miles an hour. No trouble of any kind, other than slight worries about the water-cooling system, was experienced - a fact which speaks highly for the design and workmanship of the record-breaking boat.
THE ROLLS-ROYCE ENGINE used in Blue Bird developed some 2,150 brake horse-power, and was similar to that used in Sir Malcolm Campbell’s car of the same name. A gear-box with a step-up ratio of 2:1 gave the propeller a speed of nearly 9,000 revolutions a minute. The propeller, of the two-bladed type was machined from a solid billet of tensile steel.