The only specialised marine publication in Oceania that focuses on the maritime industry, from super yachts to small craft to large commercial ships, including coastal shipping, tugs, tow boats, barges, ferries, tourist, sport-fishing craft
Issue link: https://viewer.e-digitaleditions.com/i/131029
The propulsor intakes and gearboxes Twin Volvo power below A quarter view underway boys identified that most of the developing world has large silty and polluted waterways, so if they could produce a larger commercial unit capable of surviving without the adverse effects of wear, blockage and the propulsive short-comings of a water-jet, then the company would be in a much stronger position to manufacture a marketable product. The problem was that they needed to make a quality 30 foot riverine patrol boat capable of testing completely new units for evaluation and reliability purposes. Later the same craft would be used to market the propulsors. The current test bed is a Stabicraft 10.2m Supercab constructed in marine alloy and decked out in a patrol craft manner. Powered by twin Volvo 5.5lt D6-435hp marine diesels coupled to twin experimental Contrapel drive units, the vessel has twin berths for'ard with a small marine head under the starboard bunk. The main cabin is comfortable for a crew of four with a small galley sink and fridge. Essentially designed as a day boat, there is provision for thermos flasks or to retro-fit a single burner cooker to heat a pot of stew or boil a billy. The rig is not light, weighing in at 7.8 tonnes in a laden operational mode with four crew. Add to this the very impressive trailer and the whole rig requires its own fifth wheel tractor unit to tow the beast. Fuel consumption data is being gathered along with monitoring ancillary support mechanisms for reliability and correct operation. For example, there are no extra levers or buttons to push in order to put the units into reverse or neutral. All the functions are carried out automatically on the throttle, in the same way that outboards, stern-legs or pods do. The system doesn't require sophisticated computer steering, as the boat can rotate within its own length simply by turning the steering wheel. Because there's nothing under the boat to damage, this operation can be carried out in extremely shallow water and at very low engine throttle settings. The Contrapel system maximizes the mass through-put, at the minimum pressure possible, making slow-speed control impressive. Some of the environmental features associated with the 22 Professional Skipper May/June 2013 propulsors are that they are extremely reliable even with wear and damage from ingestion of stones or similar sized objects, there's very little kinetic energy imparted to the plume, so the propulsors cause minimal disturbance to the environment and are reportedly safer for people and aquatic life. The propulsors could be used for inland fast ferries provided the hull shapes are designed to minimise wake. Barry advises that "they're much better for fragile seascapes such as underwater grass beds and coral reefs, and the totally enclosed rotating components will ensure that loss of life or mutilation through propeller-strike is no longer possible." As a result of feedback from the internet, the company was alerted to the problem of floating ropes. Industries such as crayfish using pots in New Zealand and Australia, and the crab harvesting associated with American harbours all pose problems with floating ropes, not only for propellers but for internal drive systems such as water-jets. Nylon ropes can be ingested into the unit and become wrapped around the rotating shafts. This in turn causes the nylon to fray and melt causing it to "ball-up" and consequently prevent the units from operating correctly. Removing the "bird's nest" of rope is not an easy task and can put a boat out of action for considerable time. Because Contrapel is claiming that its technology provides solutions to just about every aspect of marine propulsion and that it is a universal system, in that it carries out the function of both water-jets and propellers, Contrapel has taken the opportunity to design and fit rope cutters to the inside of the units. During extensive sea trials with full fuel tanks and crew, and remembering that this vessel is nearly eight tonnes in weight, she was still able to deliver an impressive service speed of 29.7 knots @3000rpm and a top speed of 37.25 knots @3500rpm. In looking forward, as part of their new development programme, the size and scale of the operation and the existing industry links will all have to change to accommodate future growth. Given this, it was decided to approach some leading New Zealand manufacturing companies to find out if they'd be interested in supporting the project. Contrapel intends to bring the boat up to the Hutchwilco 2013 Auckland Boat Show in May. S P E C I F I C AT I O N S LOA Beam Draft Propulsion Power Service speed Top speed Fuel Fresh water Deadweight laden 10.380m 2.930m .600mm 2 x 330 Contrapel units 2 x Volvo 5.5lt D6-435hp marine diesels 30 knots @3000rpm 37 knots @3500rpm 2 x 450lt diesel 150 litres 7.8 tonnes