To newcomers, the term "Jet Boat" potentially could suggest a craft propelled along by the a high-powered and complex engine that speeds modern aircraft around the world. Essentially, Jet Boat" is a normal boat fitted with an engine to drive a water pump or "Jet Unit". This draws water in through an intake in the bottom of the hull and forces it out at high pressure (like a Jet) through a outlet hole at the rear. Unlike a conventional power boat, the jet boat has no propeller or rudder. Instead, it is propelled along, and steered, simply by the thrust of the jet stream escaping for the outlet at the rear. Turn on a garden hose with its nozzle-end freewill demonstrate this convincingly and the feel, of its "jet" of water.
This reactionary principle was stated in Sir Isaac Newton Third Law of Motion:-
" Every action has an equal and opposite reaction &Jet boats are a perfect illustration of the principle.
In the last 30 short years New Zealand has become the home of the Jet boat These craft have conquered the world's most difficult and dangerous rivers.
But who invented it?
Controversy has raged for years over this question. A New Zealand sheep farmer, Bill Hamilton, has been said to be its inventor, but he himself never made such a claim.
"I do not claim to have invented marine jet propulsion." was his response to a critic in 1962. The honour probably belongs to a gentleman named Archimedes.
Indeed. 250 years before the birth of Christ. the Greek physicist dreamed of a water-jet craft and got close to the concept when he invented the screw for raising water. A long, hand turned device rotated within a tube. The concept surfaced again in England in 1661 in experiments by two inventors, Toogocd and Hayes. But it was only with the development of Watt's steam engine in 1765 that tangible advances became possible.
Two other British inventors, Rurrisey and Mien, designed a steam-driven pump which drew in water at the bow of a vessel and ejected it at the stern, and between 1830 and 1860 there were at least 35 applications for patents in England alone.
The most advanced type of pump was designed by Henry Bessemer of London in 1849. This was a propeller axial-flow pump with a single suction pipe running forward with twin discharges aft. Bessemer even included vanes fore and aft of the impeller to straighten the flow and compensate for losses caused by the rotation of the water. Another design by Aleixandre Hediard in 1852 harnessed the jet thrust for steering and reversing. His pump sucked water through the bottom of the ship and discharged it through an elbow. the rotation of which controlled the vessel's direction.
By the end of the nineteenth century jets had been tested in many types of craft. The idea was taken up by Queen Victoria's Admiralty just as the paddle wheel was giving way to the screw propeller in The late 186Os. The Admiralty went so far as to compare the two novel modes of propulsion. It built identical gunboats and fitted one with hydraulic jets, the other with screw propulsion The "Jet Boat" employed a 4.2 metre centrifugal pump and discharged The water through the two nozzles astern, At 760 h.p. it was capable of 17 km/h but was slightly surpassed by the screw boat which achieved 18 km/h at 696 h.p.
About the same time, several European countries were showing an increasing interest in the principle of marine jet propulsion. In 1878 just 12 years after the British experiments, the Swedish Government carried out similar tests on torpedo boats. The screw-propelled vessel recorded 18.5 km/h at 90 h.p., the jet 15 km/h at 78 h.p. A year later the Germans conducted their own experiments with a jet powered craft named the Hydro motor. Like all others before them the Germans quickly lost faith in the potential of hydraulic propulsion. In all comparative tests based on the centrifugal pump and the screw propeller, the former fared badly. Even then, however a few men did realise that jet propulsion deserved a role in specific marine applications. In 1888 Britain's National Lifeboat Institution commissioned The world's first jet lifeboat. This steam driven boat was equipped with an auxiliary' jet system designed to prevent the craft's propeller from being fouled by sand or wreckage.
In 1900 a classic book on navel architecture by Sidney Barnaby, dismissed the viability of this means of propulsion with the following explanation
There are four characteristics of the centrifugal pump which prevent it from competing successfully with propellors and paddles. These are: 1. The difficulty of getting the water through the bottom of the vessel and into the pump without checking the velocity which it already has relative to the vessel. 2. The necessity of carrying in the vessel all the water acted upon. 3. The loss caused by friction of the water in the pipes. 4. The loss due to bends in the passages.
Half-century later, Charles William Feilden ("Bill") Hamilton, had the genius, passion and force of character necessary to succeed. Born in 1899 , Bill Hamilton, spent his first 21 years on an isolated sheep farm in South Canterbury, New Zealand.
Bill Hamilton, studied books and discovered that the greater the flow the more effective the unit. But the possibilities were limited by the design of the pump, which restricted the amount of flow.
The first production unit was installed in a 4.8 metre hull that was powered by a six cylinder 65 horse power Mark I Zephyr and reached speeds up to 45 km/h. This first boat is still in existence. Only seven of these so called Quinnat models, notable for their very noisy gear box, were built for customers in 1955.
The next unit to be designed was the Rainbow unit, which operated without gears. The performance was still poor and the flow and the horse power remained low.
In 1956 saw the beginning of the Hamilton, unit as it is known today. This break Through came in 1956, when Bill arrived at the work shop one morning and happened to glance at a scrap of paper with a small sketch.
And so the first commercially viable jet unit, the Chinook two stage axial, was rapidly hammered out in the workshop.
A year later it had developed into a three stage unit capable of speeds up to 80 km/h. And it was about to attract world wide attention.
