By Shaun Summerfield
A couple of Southland blokes reckon they've found the holy grail of boating.
They've invented a propulsion system that combines the best features of a water jet with those of propellers. It means boats are more manoeuvrable and able to travel further and faster on less fuel.
It's environmentally friendly and could be used in everything from speed boats to super tankers to submarines.
They haven't reinvented the wheel, but Barry Davies and Paul Patterson have come pretty close.
“We think it's a pretty big breakthrough,” says Contrapel inventor Barry Davies.
That’s a typically Southland-style understatement from a man who is about to turn the whole idea of a boat's propellers quite literally upside down.
“The Contrapel system is a propeller system working above the waterline,” he says. “So most boats have a propeller that's exposed underneath.”
But that is only half of the story, because what makes Contrapel so special is that there are two propellers spinning in opposite directions.
It's not the first time New Zealanders have come up with alternatives to the propeller. Sixty years ago Bill Hamilton invented the jet boat – a go-anywhere craft that revolutionised river travel around the world.
The Tuatapere teacher was looking for ways improve his own jet boat nearly 20 years ago when he chanced on the idea of counter-rotating propellers.
Since then the team have almost pumped rivers dry trying to perfect the system.
Today’s 10-metre rescue boat is the culmination of two decades of hard work, Invercargill company Stabicraft happy to share in the pioneering project.
“We started with something that people looked at quite strangely and we thought it can change the mould of boating,” says Tim van Duyl of Stabicraft Marine. “If these guys can change the mould of propulsion then we'd like to be a part of that.”
Essentially, Contrapel combines the best of the jet systems and conventional propellers. Not only do they say it is more efficient, but the enclosed system is also safer and better for the environment.
“The dangers are vastly reduced,” says Mr Davies. “You will not damage the riverbed or bottom of the lake because the water is not pressurised coming out of here.”
With a patent secured, Contrapel is being released to the world, and the US Military are already looking.
“It will actually work all the way up to huge ships,” says Mr Davies. “It works equally well underwater for submarines. We want this technology to be uptaken all over the world and used in every facet of marine propulsion.”
And this is only the initial thrust. Mr Davies and Mr Paterson are already perfecting a version that allows the propellers to oscillate.
The accidental discovery, the result of faulty shaft, nearly doubles efficiency, making the boat faster and more economical.
Tests have shown the same system can also be used to generate electricity.
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