Jet sprint boat racing

Jet Sprint Boat racing is a form of racing sport in which speed boats, usually carrying a crew of two, powered by water jet propulsion rather than by conventional propellers, race around watercourses consisting of a number of interconnected channels 3 to 5 meters wide with a water depth of 1 meter.

The course

A jetsprint course typically consists of several channels interconnected by cross channels and curved sections. Often these channels join the main channels at angles other than 90 degrees while the curved sections can be either sweeping or very tight.

The race itself will consist of a predefined course through the channels with 25 to 30 changes of direction. These races generally take between 45-60 seconds.

Once qualifying is completed the competitors each run the course with the fastest qualifiers running last. The fastest 16 (typically depending on the number of competitions) proceed to the next round. This is then reduced to the top 8, then the top 4 and then the fastest two.

Classes

There are two internationally recognised classes

Class A - Engines in Class A boats are restricted to either 6.7 litre (412 cubic inch) engines with cast iron blocks and heads or 6 litre (365 cubic inch) engines with aluminium heads. Both size engines are only allowed 2 pushrod operated valves per cylinder. Furthermore the engine must be normally aspirated, using a 4 barrel caburettor. Fuel is 100+ octane aviation fuel. Typically these engines produce up to 650 horsepower

Superboats - Engines in the superboat class have no maximum size but instead have a minimum size restriction. Normally aspirated engines must have a displacement of 6.5 litres (400 cubic inch) or while forced induction (turbocharged or supercharged) engines must be at least 3.8 litres (235 cubic inch) in displacement. These engines typically are fuel injected and run methanol fuel. The small-block engines typically produce 950+ horsepower, while the big blocks can typically produce between 1000 to 1400 horsepower.

Nitromethane and nitrous oxide are not allowed.

The hull

A jetsprint hull is a typically 4 to 4.5 metres (13 to 15 feet) long. The hull's vee is usually 21 to 23 degrees with several strakes on each side of the hull. A short hull is preferred, as a longer hull takes more distance to turn and usually must be turned at a slower speed. The strakes provide "traction' by stopping the boat sliding sideways across the water when turning at high speed.

A rollcage must be fitted to the boat.

The crew

A jetsprint boat crew consists of two people. These are the driver, whose responsibility it is to steer the boat. Beside the driver sits the navigator, whose responsibility is to guide the driver through the course.

The navigator guides the driver via simple hand signals, pointing the hand in the direction that the boat must go at the next intersection or indicating the direction of a turn. If there are more than closely spaced turn the navigator will usually indicate the direction of the turn/corner by visibly raising and lowering their hand.

The Course

Originally the races were held in braided rivers using the wide banks to hold the course, however this caused problems for a number of reasons. Firstly, the shingle or sediments making up the banks of the course would be shifted by the force of the water jet propelling the boats, changing the water depth and sometimes even changing the shape of the corners. Water levels were also known to change during the course of an event, resulting in repairs being required.

Generally international jetsprint events are now held in a permanent course. This course usually takes place in a bowl as this allows all the water expelled by the jet to return to the course.

preading the word

The Jetboat was invented in New Zealand by Sir William Hamilton. Jetsprinting as an organised sport originted in New Zealand in 1981 and was introduced to Australia in the mid 1980's. This quickly resulted in a cross Tasman championship and when the sport was introduced to the United states of America a three way world championship was introduced, run under the auspices of the Union Internationale Motonautique. The championship rotates between New Zealand, Australia and the U.S.A

New Zealand drivers have tended to dominate the championships in both classes although both U.S and Australian drivers are becoming more of a threat to New Zealand's dominance of the sport.

ee also

* sport
* Offshore Powerboat racing