Celebrating 100 years of tethere

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Celebrating 100 years of tethered hydroplane racing

The balance of power shifts.

From the first record set by Teague and Delves-Broughton in 1908, through to 1936, flash steam powered boats held the outright speed record, but the balance of power was changing. Back in 1913, Fred Westmoreland had noted that, despite his best efforts, the steamers were significantly faster than his IC boats. Hardly surprising as the IC motor was in its infancy and those available for model boats were large and heavy, usually involving them being mounted horizontally. Very basic carburettor and valve technology along with rudimentary ignition systems produced a low powered, slow revving power unit. Simple to operate compared with a steamer, but sadly lacking in horsepower.


H.H. Groves' Ultra lightweight single cylinder flash steam plant from 1912	Groves' record breaking twin cylinder steam plant. 24.25 mph in 1914	Stuart Turner AE illustrates the size and weight of four-strokes from the period.

As is often the case, during the four years of war, IC engines made very rapid advances, which carried over into motorcycle and car racing once hostilities were over. Through the 20s, a number of enthusiasts incorporated full size practice into engines for their racing models. A change in rules seriously handicapped the flash steamers and the last record ever to be set by one, was Stan Clifford’s 43.3 mph with Chatterbox III in 1926. It was to be another 10 years though, before an IC engined boat exceeded this.

By 1930 four stroke engines suitable for use in A class tethered boats were being produced commercially by Stuart Turner, Bond’s, and Grays, with the F.N Sharp inspired Grayson, and its badge engineered clones. These were proving relatively reliable and successful, especially when given some detailed tuning attention. It was, ultimately the home built single cylinder four strokes that would eclipse the flash steamers and rule the roost until they in turn were surpassed in the late 40s by the two-stroke motors.

The Grayson style variants, as breathed on by Mr Sharp, were also producing excellent results at regattas. A number of dedicated and highly skilled enthusiasts took these basic designs and turned them into highly successful and well recorded racing four strokes.
Right- Sharp variant of the 'Grayson'

There were many of these well designed and engineered motors in use, but from the point of view of the outright speed record, the most significant were the two 30s built by the Innocent Brothers and Ken Williams. In terms of race success Stan Clifford, forsaking his flash steamers and George Noble who had also ‘changed sides’, joined these two. This is not to detract from the many other very successful competitors, but ‘Betty’, ‘Faro’, ‘Bulrush’ and ‘Blue Streak’ would dominate results for many years to come.

Left: Bulrush 8

At the front of the motor is a clockwork mechanism that opens the throttle and advances the ignition at the same time. It is wound up before starting the engine and tripped as the boat is released. A small fan acts as a governor to control the rate of the adjustments. Betty and Faro both used a hydraulic system that only worked on the ignition.

None of these engines arrived ‘out of the blue’ as the design, construction and development to record breaking speeds was a long and laborious process, which would continue throughout the life of the boats and engines. Because of changes in design, developments, breakages and accidents, the best-known boats and engines were very much in the ‘crossing keepers broom’ domain. Given the continuous history of three of these boats to the present day we are lucky to be able to look in some detail at the engines that took on the mantle of 'record breakers' in the 30s.

Betty

With the exception of Ken William’s design, virtually every other successful motor shared the same layout as the Sharp motor, which in turn was derived from castings supplied by Economic Electric. The aluminium crankcase was split vertically with mounting lugs on each side. A single camshaft was directly driven of the end of the crank with two pushrods running up the front (or rear) of the engine. A single finned cylinder was either spigotted into or bolted onto the mouth of the crankcase and there was the basic assembly. The cranks would normally use large outside flywheels, although some did have full circle cranks and a small starting pulley. It was the cylinder heads where most of the development and variation could be found.

The basic Bond’s/Grayson layout was positively archaic with two parallel valves and a flat topped piston that severely restricted performance. Most builders looked to the current racing motorcycle engine for inspiration and it is easy to see the influence. Hemi-spherical combustion chambers with radial or inclined valves, often using hairpin valve springs, would sit atop the motor, almost always with the carburettor and exhaust across the boat. A domed high compression piston would make the most of the improved breathing from this layout and the more exotic fuels being used.

The ‘odd one out’ of these motors was the one Ken Williams designed and built for ‘Faro’. Firstly it was cast in magnesium, but the most obvious difference was in the camshaft that lay along the side of the engine, driven by a train of spur gears in a timing chest. The cylinder head, of which there were at least 4 during the life of the engine, is again unusual with the carburetter and exhaust lying fore and aft in the boat, rather than cross-wise. Motors built from Ken Williams’ castings also found their way into several other boats but with far less success. What most of these motors did have in common were ingenious devices to assist the boats in getting away, such as ignition timing being automatically advanced by a clockwork timer, oil filled dashpot or other means.


Rebuilt 'Faro' motor as run from 1944-52. Few original parts.	Magnesium crankcase 1935-44 replaced when the lug cracked	Original head and carburetter used in the 1930s	Oil filled dashpot to advance the ignition as boat speeds up.

There were many other highly successful four stroke singles built through the 30s and into the 40s by the likes of David Innes, Bill Brightwell, Mr Mitchell, Bob Kerswell, Ernie Clark and Bert Stalham to name but a few and these were all variations of the same basic design.

The only significant difference being that some used two separate camshafts side by side rather than the one. Several dedicated engineers did explore more advanced designs with chain and gear driven overhead camshafts, twin overhead camshafts, parallel twins, opposed twins, vee twins and even superchargers, but none of these improved on the performance of the well-sorted basic engine.

Left: David Innes' Satellite III

The four engines described were continuously developed until the boats had doubled their original speed, but as Edgar Westbury was to comment in 1954, they were still using the original scow hulls with submerged props to the end of their racing careers.

How much quicker might they have gone with more modern hulls and surface props? Sadly we shall never know, but Norman Lara showed the potential of the four-stroke single as he edged ever nearer to 100mph with Vic Collins’ ‘A’ class boat. (Seen right)

As the four-stroke eclipsed the flash-steam powered boats, so they in turn succumbed to the two strokes, but that is another story.