Oasis 10m Rigid Tube Monohull

When Boyd and Jan Humphries sold their Southland farm they decided to merge their love of boating with a lifestyle change. After investigating various commercial boating opportunities in and around the Southern Lakes area, they settled on Lake Dunstan and the challenge of creating a new venture from the ground up. Paul Smith reports.

Oasis 10m Rigid Tube Monohull
Oasis 10m Rigid Tube Monohull
Unlike the other major lakes in the area - Whakatipu, Wanaka and Hawea - Lake Dunstan is the result of the extensive engineering programme that created the Clyde Dam on the Clutha and Kawarau Rivers.

The formation of Lake Dunstan saw much of the old town of Cromwell submerged, some of the country's best "white water" pacified, and much of the Otago gold rush history lost in its murky depths.

That the dam was constructed on a major fault line also raises an eyebrow or two... nevertheless, the lake exists, new Cromwell town is thriving and the recreational opportunities offered by the lake are improving all the time.

Boyd and Jan Humphries saw an opportunity to develop a charter operation on the lake conducting scenic cruises, fishing trips and the like. Boyd attended the Auckland Boat Show but could not find a boat which fitted his vision from those on offer - most production boats of sufficient size incorporated sleeping accommodation which was not required for use on the "small" lake.

Further, Boyd had a preference for GRP construction but most production designs he looked at were in alloy. On the recommendation of a couple of Invercargill-based manufacturers, Boyd approached designer Scott Robson with his specific requirements.

Scott Robson was quick to appreciate the Humphries' requirements since they were similar to those for Robson-designed craft operating in eco-tourism ventures in Canada. Based on the proven deep vee (20 degree deadrise at the transom) hull form utilizing two planing strakes either side of the keel and wide, turned down (15 degrees) chines, the hull design offers good rough water handling capability.

The incorporation of rigid tubes (pontoons) around the perimeter of the hull endows the design with exceptional reserve buoyancy and stability both at rest and when cruising. In this case the tubes are formed from closed cell foam, the surface of which is further protected by "Rhino" vinyl coating as used in wellside truck decks. At higher speed in calm water the pontoons ride clear of the surface. Scott Robson began to incorporate rigid tubes in many of his designs from as early as 1997.

The owners accepted the design in August 2004 and commissioned Davie Norris Boat Builders Ltd of Christchurch to complete construction and fit out of the vessel. GRP was the preferred construction medium for reasons of quiet operation, refinement of finish and a good solid feel on the water.

The male moulds were constructed using CNC cut profiles and from there, the solid laminate was laid up according to specification as designated by David Lyons of NuPlex in Sydney. On completion of the laminate lay-up, the hull was faired and painted to a high standard of finish.

We didn't listen to any music during our time on the boat, but if you're that way inclined, it's easy to imagine rocketing out to your favourite dive or fishing destination - accompanied by Deep Purple's Smoke on the Water - and believe that's all nearby boaties will see as you whistle by.

The foredeck area is protected by a solid stainless steel bow rail but seldom will crew need to go for'd since anchoring is controlled from the helm with a capstan, well designed fairlead and enclosed anchor locker.

Access to the spacious forecastle down two steps from the cockpit sole, is via a wide central lockable door. This houses the head, a vanity and handbasin, and three large lockers. To port, the open hardtop houses the bar countertop with the drinks locker and two drawers beneath, while two utility drawers are set into the bulkhead above.

The bar showcases locally produced Bannockburn wines and Benger Gold juices. When not required, a small crew seat folds up flush against the coaming. A portable gas heater is also stowed in this area for use on those sometimes chilly southern evening cruises. To starboard is the helmstation. Yamaha digital gauges include a tachometer for each engine, a speedometer and fuel management.

Immediately ahead is provision for mounting the laptop computer which also displays GPS and fishfinder functions. Gang switches for other functions are located on the starboard coaming below the Yamaha remotes. A VHF radio and CD/DVD player complete the electronics package.

The helmseat is adjustable fore and aft and is mounted on a solid pedestal with storage beneath. Seating for 20 passengers in two rows has storage for lifejackets etc under each unit. The entire cockpit area is protected by a canvas cover and can be completely enclosed with clears.

The cover is supported by a sturdy stainless steel framework extending aft from the hardtop to the transom. Batteries are contained in an underfloor locker at the rear of the cockpit ahead of which are two fuel tanks with a 500-litre total capacity, and a 200-litre effluent tank. The engines are located centrally with generous boarding platforms either side.

The main item in the electronic package that sets this boat apart from many others is the "Majestic" underwater camera. This is mounted off the transom and beams underwater images back to a flat screen TV monitor mounted centrally from the roof of the hardtop. It is expected that passengers should be able to view sections of old Cromwell town now submerged after the formation of Lake Dunstan.

Performance & Handling
Twin Yamaha 200hp four-stroke, counter-rotating outboard engines power this 3.5 tonne craft. While the boat will hold a very comfortable cruising speed of 20 knots at 4600rpm, the sightseeing application sees the boat spending much of its time at displacement speeds of less than 10 knots with the engines idling along at around 2000rpm. It is of course extremely quiet and fuel-efficient at such times. The engines will happily rev out to 5800rpm pushing the craft to a top speed in excess of 30 knots.

Lake Dunstan is not usually subject to rough water conditions and on the day we sampled the boat, gusty nor'west winds succeeded only in creating a slight white cap chop which Oasis disposed of with disdain. We found the boat responded well to helm inputs with the pontoons limiting heel in sharp turns and ensuring a very high level of stability both underway and at rest.

There was no obvious need for trim tabs despite being buffeted by strong crosswinds. We believe the boat would be extremely competent in rough offshore conditions even though it is most unlikely to encounter such conditions in its existing environment.

Oasis comfortably meets the criteria established by her owners for space, stability and speed capability. The boat is very well finished and a tribute to the painstaking attention to detail by her builders, Davie Norris Boat Builders Ltd of Christchurch. Boyd and Jan Humphries are pleased they sought professional assistance from Scott Robson in the planning and design of the new vessel to ensure the end result fulfills the requirements of its intended use.

Oasis - 10m Rigid Tube Monohull
price as tested $300,000
LOA: 10.28m
Beam: 3.54m
Engines: 2 x Yamaha 200hp, four-stroke, counter-rotating
Displacement: 3.5 tonnes
Owners: Boyd & Jan Humphries, Cromwell Cruizez (Ph/Fax:(03)4453002)

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