Gold Cup Racers Aim at 200 Miles per Hour 
Thrills and excitement-the roar of powerful motors — the flying "rooster tails" and the terrific speeds — these are the ingredients that have skyrocketed unlimited hydroplane racing as a spectator sport. Two million people will watch the big jobs race before the end of this season and a vaster audience will watch and listen over TV and radio.
The unlimiteds, often called the Gold Cuppers, are shoving the 190-mile mark on straightaway runs. Experts think a new world record of around 200 miles per hour for propeller-driven boats will be set this year.
The annual contest for the Gold Cup is the big race. Unlike any other trophy in speedboat racing, the Gold Cup is defended on the home waters of the winner of last year's race. Miss Thriftway of Seattle won the cup in Detroit in 1956, so this year Seattle plays host. Half a million frenzied spectators will jam the shore line adjacent to the course and hundreds of private boats will be tied rail-to-rail in every available location.
After Seattle the unlimiteds will race in Detroit August 31 for the Silver Cup, an event that annually draws some 350,000 spectators. The race for the President's Cup on the Potomac is next, followed by the International Cup race at Elizabeth City, N. J., with the season winding up at Lake Mead, Nev., with the Sahara Cup race October 12 and 13.
All this is a far cry from the dreary unlimited picture of 10 years ago. The fastest heat in the 1947 Gold Cup race was turned at an average of 56.8 miles per hour by a boat powered by a 1500 horsepower engine. Meanwhile the little 135-cubic-inch hydros were averaging 70.5 miles per hour with tiny Ford V-8 "60" engines. Spectators stayed away from unlimited racing.
Curiously, the boat that changed the whole Gold Cup picture and that set phenomenal records on the water was conceived as a pleasure boat. In fact, it was used strictly for pleasure until its owner, Stanley Sayres of Seattle, found he was breaking the world record every time he took a friend out for a spin.
The extraordinary craft was designed by Ted O. Jones, who was working at Boeing at the time and who applied aircraft engineering principles to the three-point hydroplane design. The boats are called three-pointers because at high speed they ride on the trailing edges of their two outboard sponsons and on one blade of the propeller. The hydros are tricky. If the bottom of the hull isn't shaped exactly right the boat will not get up off the water. On the other hand, too much air under the hull makes the boat kite and possibly flip backward.
Slo-Mo-Shun IV, the boat Jones designed for Sayres, looked much like the other hydros but there were some important differences. Slo-Mo trimmed out in perfect balance at high speed. It had a "spoiler" under the bow to break up the flow of air and keep the bow from rising too high. There was a big air fin to help the boat track straight at high speed, offsetting the sidewise thrust of the propeller.
The unlimited hydros had a tendency to break apart in rough water even though their speeds were not sensational. They were heavy, but poorly reinforced. Jones used aircraft principles of construction to produce a light boat that could take a beating and not fall apart. Tanks and instrument installations were other sources of failure, and again Jones went to aircraft procedures.
At high speeds a floating pop bottle or a small piece of drift will smash right through the bottom of a racing hydroplane. Jones sheathed the sponson runners and the bottom of the hull with dural plate. He put in a special gearbox to reduce the chance of mechanical failure. He installed hydraulic steering and placed the rudder to the left of the centerline to get it out of the prop wash.
After a number of trials and adjustments, Slo-Mo got up and literally flew across the water. Sayres found that the needle of his water speedometer was banging against the pin on every run and the speedometer was calibrated to 150 miles per hour. The boat rode so smoothly that it seemed impossible to Sayres that he could be going faster than the world speed record of 141 miles per hour, set by the late Sir Malcolm Campbell in 1939. And he was using a stock Allison aircraft engine.
The speedometer was checked and found accurate. A special 200-mile-per-hour speedometer was built for the boat, the first ever designed. Slo-Mo went on to set a world speed record of 160.323 miles per hour and later won the Gold Cup and Harmsworth Trophy races.
Today, unlimited hydroplanes designed by Ted Jones hold every unlimited record in the book and most of the important cups and championships. Even the boats designed by others show the Jones influence. The annual battle for the Gold Cup has become a feud between Seattle and Detroit, home of many of the fastest Eastern boats.
In the past you virtually needed to be a millionaire to own and race one of the big boats. It's by no means a cheap sport today. You can spend $50,000 on a boat and its equipment. A single propeller, for instance, costs $500 and if you want real quality you can buy a propeller machined from a forging for $1000. Different water conditions and different courses demand different propellers for peak performance. Counting spares, an owner may invest $4000 to $8000 in propellers alone.
An owner wants spare engines, too. A blown engine used to mean a boat was out of the race. Now the owners with the necessary cash carry spare engines, each complete with its own gearbox, all ready to drop into the hull. A trained crew can change an engine in 40 minutes.
Ted Jones has an improved design of boat on the water this year and the unlimited-hydroplane fraternity is looking it over with a critical eye. Jones has retained all the principles of the airfoil hull and the tunnel between the sponsons in the new boat, Thriftway, Too and has added new features. One of them is that the driver sits ahead of the engine instead of behind it. Riding in front, he isn't cooked by the heat of the big engine and he isn't deafened by the thunder of its exhaust. He gets a smoother ride in rough water, has better visibility and is in less danger in case of fire, explosion or shaft failure. The quiet cockpit allows the use of a short-wave radio to the pit.
The new Thriftway, Too weighs 6552 pounds, more than most hydroplanes, and is 34 feet long, four to six feet longer than most. Beam is 13 feet. The hull is of a special 5-ply mahogany plywood, a quarter inch thick on the bottom. For extra protection a dural plate is bonded to the bottom of the hull.
Six fuel tanks of 44 gallons capacity each are placed so that the trim of the boat does not change as the supply of fuel diminishes. The tanks are of stainless steel covered with glass fiber.
The boat's vertical stabilizing fin is larger than in previous boats and has the usual trim tab on its trailing edge that helps offset propeller torque. A new feature is a pair of small horizontal fins near the top of the vertical fin. These small airfoils help lift the stern of the boat up off the water at high speed.
Thriftway, Too has a large engine compartment that at present contains a supercharged Rolls-Royce aircraft engine delivering about 2500 horsepower souped up for racing. Jones wanted the compartment large enough to install two engines if necessary but the boat proved so fast in early season trials that he may not need a second power plant. Instead, he may install a small engine ahead of the main power plant simply to drive the blower. This would relieve the main engine of a drag of at least 500 horsepower and would allow the supercharger to be driven at constant speed, materially reducing the chances of blower failure.
Propeller shaft of the new boat is 1¾ inches in diameter, of tough "K" Monel, and the propeller is 13½ inches in diameter. The selection of propellers made up for the boat ranges from 20 to 24 inches in pitch.
Jones hopes that Thriftway, Too will start a new era in unlimited hydroplanes, with a corresponding upward jump in the world record for propeller-driven boats. But already he is looking ahead to something else. He has a jet hydroplane in mind, and has done some preliminary planning. In appearance the jet boat would look very much like Thriftway, Too with the same over-all dimensions but with a higher, fatter cowling to hold the jet engine. The vertical fin would be taller. The hull would be entirely of dural, glass-fiber covered.
These plans are based on using the J-47 jet engine, a power plant that develops 6200 pounds of thrust. This is a bigger engine than the jet used by Donald Campbell in setting his world water record of 225.63 miles per hour in the Bluebird, and Jones sees no problem in getting the speed up to 300 miles per hour. A pure jet boat would be strictly for setting records; eventually we may have competition racing between boats powered with gas turbines hooked to the propeller shaft.
(Reprinted from Popular Mechanics, August 1957, pp.82-86)