Alloy Boats AB 1500

From aluminium house boats to power catamarans, Tauranga’s Alloy Boats has a knack of finding niche markets within New Zealand’s competitive marine environment. The company’s new 50-foot aft-cabin, power catamaran Kazara is a case in point.

Alloy Boats AB 1500
Alloy Boats AB 1500
Untitled Document Designed and built by Kim and Colin Bertelsen at Alloy Boats Tauranga factory over 18-months, the Kazara project cements Alloy Boats’ reputation for design innovation and quality alloy construction.

Alloy Boats started production in 2001 under the Lazy Days Houseboats banner. Kim had recently returned from Canada with his Canadian wife and child and sought an opportunity to begin boat building. An aircraft engineer by trade, he saw a niche for houseboats on Tauranga Harbour.

It was the start of a new career that has taken on a life of its own. In recent times the company expanded to include a trailer boat range, a "Leisure Cat" range and, now, a growing power cat range. Kim changed the name of the business to Alloy Boats in February 2006 to better reflect the diversity of boats being built.

Curvaceous and bold, Kazara falls somewhere between a large luxury vessel and a practical live-aboard cruiser with offshore capabilities. Kazara is Colin Bertelsen’s own vessel and was built in partnership with his son Kim.

While principally designed by Kim, Colin had a large say in the final shape and layout of the boat, which reflects his many years experience and passion for game fishing. The founding editor of Tauranga’s Bay Fisher magazine, he also has a keen eye for aesthetics and this is obvious from Kazara’s on-the-water profile.

While it is one thing to build large vessels from aluminium, it is quite another to achieve an end product that mirrors fibreglass or timber in terms of its look and feel without excessive and expensive fairing of topsides and superstructure
Kim Bertelsen says very little fairing was required on Kazara which is remarkable given that the alloy panel work was cut by hand from loftings rather than pre-cut CAD drawings. It was, says Kim, a labour intensive and time-consuming job but the results reflect what can be achieved with attention to detail. He says CAD drawings will be extensively used in future builds which will reduce build costs and time.

From a design perspective both Kim and Colin wanted to create a well-proportioned boat more in keeping with a large modern mono-hull rather than the box-like structures common to power cats. The way to achieve this, they reasoned, was to build in long deck and cabin top overhangs to add perspective while creating large radii in the superstructure panel work to soften the look of the boat.

This is most notable aft where excessive curvature of the transom and boarding platform has created a stylistic and sophisticated look. This theme has been extended through to the cockpit and the exterior flybridge staircase to good effect
The internal layout largely reflects the boat’s aft master cabin on the starboard side. Aft cabins are something that we see little of in New Zealand but are a feature nonetheless that gives the boat huge potential as a genuine cruising and live aboard vessel. Colin says this was a non-negotiable feature regardless of the implications it had on the final internal layout.

"Once you have experienced the benefits of an aft cabin in terms of additional accommodation, spaciousness and quietness away from the slap of chop at the bows, you wouldn’t have it any other way."

Interior layout

With a beam of 5.1m and an overall length of 15m, Kazara provides a big platform from which to craft an interior that owners of 60-foot mono-hulls would die for. The stability of twin hulls also provides opportunities to create open-plan living spaces that would not be so practical on a mono-hull.

With this in mind Colin and Kim have created a very open saloon amidships that incorporates a domestic size galley to port and a U-shaped dinette to starboard. Hand crafted from solid Rimu timbers and veneers, Colin’s self-taught joinery skills are excellent.

The boat is fully lined from stem to stern with generous use of soft flowing curves in the oiled timber joinery to create a modern yet ship-like feel. Carpeted throughout, with colour-matched leather upholstery and vinyl ceiling and wall-liners, Kazara is opulent yet inviting and homely. The galley features domestic-sized appliances and counter tops with masses of cupboards and drawers, again reflecting the boat’s live-aboard status.

The saloon opposite is set around a fixed dining table that caters for four comfortably and six at a squeeze. The saloon is light and airy with a full width windscreen forward and large fixed side windows giving uninterrupted views through 180 degrees. Perhaps the only disappointment is not being able to fully enjoy the view while seated at the saloon table. Kazara has massive headroom in the saloon and it should be possible to raise the height of the saloon table and settee to enjoy the view.

Saloon access from the cockpit is via a single aluminium door on the port side and a short corridor with recessed lockers to starboard housing the boat’s electrical switchgear. Opposite an enclosed locker opens to reveal a fabricated rod holder welded onto the inside of the hull.

This keeps rods securely fastened and accessible yet out of the way. It is one of numerous small touches that are not immediately noticeable. At the head of the companionway to port two stairs lead down to the main head and shower.

This, like everything on Kazara, has been fabricated from aluminium and coated in crisp white two-pot marine paint. While perhaps a bit on the small side for a boat of this size, the build quality is excellent.

The main head is at the rear of the shower stall, which is a bit unusual. There is no overhead hatch but a sealed port provides some light. The bathroom vanity is built from solid Rimu with a domestic size sink and cabinet. Again, solid Rimu cappings and a timber parquet floor give the boat a traditional and warm ambiance.

Master cabin

The double master cabin is opposite the bathroom to starboard and down two stairs. Square in shape, the double berth is positioned fore and aft with the headboard on the internal bulkhead. The cabin is fully lined with generous use of Rimu and vinyl liners. A solid Rimu vanity has been built into the aft of the cabin with a sink and hot and cold water.

Personal storage is very good with three very large lockers built into the side of the hull. Twin hatches open into the cockpit and a side port provides plenty of natural light. There is generous standing headroom and sitting headroom in bed. The live-aboard theme continues with a full length book case, his and hers reading lamps and a Rimu bedside table.

Most of the doors on Kazara are keyhole shaped and crafted from solid timber. The master en suite is forward and down two stairs. This is very similar to the main day head and shower with the electric toilet at the rear of the shower stall. Parquet flooring and timber cappings lend a homely feel.
Colin says he spends two or three nights a week on the boat for no other reason than it’s a nice place to be. He says his wife is particularly appreciative of the domestic style of the master cabin and its location aft, which is both quiet and stable when at anchor.


The enclosed flybridge can be accessed from the external spiral staircase in the cockpit and internally via a six-step solid Rimu companionway amidships of the saloon. The helm station is set to starboard and flanked with a comfortable wrap around L-shaped settee upholstered in hardwearing vinyl.

The bridge enjoys uninterrupted views and is well laid out with everything falling nicely to hand. The main fascia is fabricated from aluminium and trimmed in Rimu. A large-screen Furuno NavNet system is set between SmartCraft engine management gauges along with VHF radio, BEP switches and Maxwell windless remote and chain counter.

The flybridge screen is angled well back providing a substantial dash area forward of the helm. Kim says this is a prime spot for spreading out with cushions and a book when game fishing or riding to the anchor.

"Everyone gravitates to the flybridge because it’s a sun trap. We chose to put in very wide squabs to provide additional accommodation if required. It’s my pick of berths and we spend most of our time up here."

Colin, ever mindful of the exterior profile of Kazara, reduced flybridge headroom to about 5’10". This, he says, ensure that the flybridge superstructure does not throw out the proportions of the boat. "This can be raised in future builds to accommodate taller owners but it’s just right for us."

Central French doors open outwards to the flybridge cockpit, which has a curved aft bulkhead, fitted with a stainless steel six-gang rod holder. Like the cockpit below, the sole is lined in Tek-Dek synthetic teak. A wide and comfortable L-shaped settee provides the perfect place to kick back on hot summer days.

Forward cabins

The forward cabins are identical in layout with keyhole doors opening to full size double berths, each with their own solid Rimu vanities with hot and cold water. Each berth has a large open locker built into the bed head with additional storage cupboard built under the aft end of the berth.

Overhead hatches and a single sealed port provide natural lighting. A curved step takes care of the climb in and out of bed. Fully lined and carpeted, the forward cabins are woody and homely. Opposite each cabin is a single quarter berth running back under the saloon and galley. In standard trim Kazara will swallow up three couples and two singles in dedicated cabins. Bring the flybridge and saloon into the equation and you have a ready-made slumber party for no fewer than 10.


Shapely and large, the cockpit on Kazara is a statement in design with its curved transom and double gate doors, wide Tek-Dek-lined combings and sole and centrally mounted game chair. The boarding platform faithfully mirrors the cockpit shape and design with rounded ends that, collectively, create a level of sophistication more common to European imports.

Colin’s experience and passion for fishing has been catered for with huge live bait tanks recessed into the transom, tuna pots, bait station and large external freezer built into the aft bulkhead. The engine access panels are flush mounted into the cockpit sole and remotely operated. The flybridge overhang provides all-weather protection with strategically placed down lights for night fishing.

Storage options abound with lockers built into the combings and aft saloon bulkhead. The central curved transom island is equipped with twin sinks and provides storage within for the boat’s gas bottles, BBQ and wash down pump. Kazara’s side decks are wide and flat with continuous stainless steel rails running the complete length of the hull.

The foredeck is huge and inviting as too is the Maxwell 2200 windless mounted centrally on the bow. As a game fisher of some repute it is not surprising that his twin game poles are remotely operated from the bridge. Externally, Kazara carries a very substantial rubber-lined belting with a second belting protecting the transom and boarding platform.


Kazara’s hull is fabricated from 6mm marine grade alloy to the waterline with 5mm topsides and 4mm superstructure. The hull is conventionally built on stringers and frames with solid watertight crash bulkheads forward. The cockpit is self-draining through deck scuppers with a series of automatic bilge pumps strategically located throughout the pontoons.

While Kazara was not built to be put into survey, the design and construction methods used are to survey requirements. From bow-on it is surprising how much rake Kim and Colin built into the wing deck joining the pontoons. Colin says this very effectively negates the effect of wash riding up the internal sides of the pontoons and keeps sea noise to a minimum.

Kazara is powered by twin B-series 425hp common-rail Cummins diesels with 2:1 twin disk V-drives swinging a pair of 23x21 four-blade propellers. The onboard systems are all 12 volt and kept in check with a 4 KVA Onan genset and a 140-amp high-output alternator on one engine. Hot water is from the engine with gas to the galley.

Tankage volumes are generous with 2000 litres of diesel in twin alloy tanks and 900 litres of water in a single alloy tank and a 180-litre holding tank. Fully laden Kazara weighs 17 tonnes. Colin has kept onboard systems to a minimum and as simple as possible.

"When systems fail owners go looking for answers from the boatbuilder and not the manufacturer of the failed equipment. Simple robust systems ensure reliability and long service life. No one wants to have to spend their holidays with an engineer onboard to keep everything functioning."


Handling such a large vessel is not for the faint-hearted but Colin proved on several occasions that he could turn the vessel in its own length and berth it without any assistance. "I often go out on my own mid-week for a few hours fishing. Like everything else it’s about technique but it is not hard." The view from the flybridge provides all-round visual awareness so size in this instance does not equate to difficulty. Remotes in the cockpit provide a useful back-up when reversing into tight berths.

On a beautifully calm Tauranga day Kazara finds the plane at about 12 knots with 1800rpm on the engines. Colin typically cruises at 20-22 knots with the engines ticking over at about 2300rpm, each using about 47 litres-per-hour. This gives Kazara a comfortable range of about 450 miles. Push the throttles forward to 2700rpm and the boat will fast cruise at 25 knots with fuel consumption of 55 litres per hour.

At wide-open-throttle (3000rpm) Kazara powers up to 28 knots at 82 litres per hour. Colin says when he and his wife go cruising alone they often steam the boat at about nine knots. This not only keeps marital relations harmonious but also delivers excellent seven litres-per-hour fuel economy. "We’ve found a 10-hour game fishing days costs us about 140 litres. This is surprisingly affordable when you share costs among the crew."

Power cats are all about comfort at sea and Kazara is about as good as it gets. Engine noise and vibration from the Cummins diesels is minimal from the flybridge. The boat levels out nicely with power on and responds well to her hydraulic helm and throttles. Flat sea conditions are no test for a vessel’s manners but Colin says he has seen three to four metre swells and has powered on regardless. From my seat at the helm Kazara feels every foot her size, powering out to sea with the Mount disappearing rapidly behind. This is cruising at its best.

Specifications: Alloy Boats AB 1500 (Price as tested $ 1.1 million)
Designer: Kim Bertelsen
LOA: 15m
Beam: 5.2m
Displacement: 15000kg
Power: 2 x 425hp Cummins
Fuel: 2000 litres
Fresh water: 900 litres
Draft: 1.3m
Empty weight: 14000kg
Laden weight: 17000kg

Alloy Boats, 25 Montgomery Rd, Judea, Tauranga
For more information email or visit

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