Prowler NZ10.4 Power Catamaran - Evolution of the Design

The evolution of my interest in power catamarans began in the late 80's when producing the Malcolm Tennant designed Northern 11.

When Tennant was grilled on why, if a Northern 11 could sail at speeds in the low 20's without planing, this could not be achieved in a powerboat? Malcolm replied that it could but you had to overcome the problem of stern squatting caused by the centre of propulsion being low down (underwater) rather than high up (in a rig) as it is in a sail boat.

However, he thought it a solvable problem and designed Icarus, a 14m powercat, the first of what was to become the Icarus range of powercats. With a pair of 250hp Cummins engines she cruised very economically at 20 knots and achieved a top speed of 25 knots. The Icarus range were mostly commercial ferries but did include some pleasure boats and ranged in size from 12m - 22m.

Thirteen were sent to Hong Kong to ferry workers on the 18 mile trip to and from Chop lap Kok, the island site of the giant new airport project. There were ferries of similar size from many manufactures plying the same route for the numerous companies involved.

Our cats included 40 passenger with 2 x 105hp engines operating speed 18 knots, 50 passenger with 2 x 140hp engines operating speed 20 knots and 60 passenger with 2 x 230hp engines operating speed 25 knots. None of the opposition came close to matching the Tennant Cats in terms of consistent trip times in all conditions, comfort of ride, and most importantly fuel efficiency.

This last factor is critical in commercial boats working flat out 18 hours a day 6 days a week, year round.

In 1997 I purchased the 1912 Arch Logan designed classic launch Coquette and began a love affair that would lead to cloning the old girl with fibreglass moulds. For the best part of a decade we produced some 40 Logan 33's all decked out so that the uninformed inevitably mistook them as the perfect restoration of an old timer.

The narrow round bilge hull requires very little horsepower and subsequently little fuel providing it remains in displacement mode. The downside is that hull speed is under 8 knots.

However, a displacement hull powercat has the nice slow boat (displacement hull) ride and efficiency but will produce much greater speed.

A trip to Australia and a chat with leading Aussie multihull designer Jeff Schionning showed that some astute powercat designers had worked on Tennant's approach and added their own touches. This contact led to our purchase of the moulds for Schionnings earlier Prowler 9000, a proven performer but with limited accommodation.

We were just going to tweak it a bit but ended up lengthening the hulls to 10.4m and re designed the top. This lifted it several levels in terms of accommodation to a very comfortable cruiser.

We knew from our ferry days that extra weight and length virtually cancel each other out and the performance/horsepower ratio would remain pretty much the same.

Yamaha make a nice suitable 4 stroke big gearbox engine with the necessary extra long shaft and the result is a boat that has superb accommodation, manoeuvres and rides like a dream, goes like the clappers and runs on the proverbial smell of an oily rag.

EVOLUTION COMPLETE....


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Design Evolution The evolution of my interest in power catamarans began in the late 80's when producing the Malcolm Tennant designed Northern 11. When Tennant was grilled on why, if a Northern 11 could sail at speeds in the low 20's without planing, this could not be achieved in a powerboat? Malcolm replied that it could but you had to overcome the problem of stern squatting caused by the centre of propulsion being low down (underwater) rather than high up (in a rig) as it is in a sail boat. However, he thought it a solvable problem and designed Icarus, a 14m powercat, the first of what was to become the Icarus range of powercats. With a pair of 250hp Cummins engines she cruised very economically at 20 knots and achieved a top speed of 25 knots. The Icarus range were mostly commercial ferries but did include some pleasure boats and ranged in size from 12m - 22m. Thirteen were sent to Hong Kong to ferry workers on the 18 mile trip to and from Chop lap Kok, the island site of the giant new airport project. There were ferries of similar size from many manufactures plying the same route for the numerous companies involved. Our cats included 40 passenger with 2 x 105hp engines operating speed 18 knots, 50 passenger with 2 x 140hp engines operating speed 20 knots and 60 passenger with 2 x 230hp engines operating speed 25 knots. None of the opposition came close to matching the Tennant Cats in terms of consistent trip times in all conditions, comfort of ride, and most importantly fuel efficiency. This last factor is critical in commercial boats working flat out 18 hours a day 6 days a week, year round. In 1997 I purchased the 1912 Arch Logan designed classic launch Coquette and began a love affair that would lead to cloning the old girl with fibreglass moulds. For the best part of a decade we produced some 40 Logan 33's all decked out so that the uninformed inevitably mistook them as the perfect restoration of an old timer. The narrow round bilge hull requires very little horsepower and subsequently little fuel providing it remains in displacement mode. The downside is that hull speed is under 8 knots. However, a displacement hull powercat has the nice slow boat (displacement hull) ride and efficiency but will produce much greater speed. A trip to Australia and a chat with leading Aussie multihull designer Jeff Schionning showed that some astute powercat designers had worked on Tennant's approach and added their own touches. This contact led to our purchase of the moulds for Schionnings earlier Prowler 9000, a proven performer but with limited accommodation. We were just going to tweak it a bit but ended up lengthening the hulls to 10.4m and re designed the top. This lifted it several levels in terms of accommodation to a very comfortable cruiser. We knew from our ferry days that extra weight and length virtually cancel each other out and the performance/horsepower ratio would remain pretty much the same. Yamaha make a nice suitable 4 stroke big gearbox engine with the necessary extra long shaft and the result is a boat that has superb accommodation, manoeuvres and rides like a dream, goes like the clappers and runs on the proverbial smell of an oily rag. EVOLUTION COMPLETE....