Powercat purrs after redesign

The 15.2-metre Equinox 7 is likely to be seen on other shores, too. Photo / Supplied

Roger Hill's latest design shows he's on the top of his game.

Aucklander Hill has to be one of our most versatile designers. His portfolio contains both monohull and catamaran designs and both powerboats and sailing yachts.

As it says on his website, virtually every design has been commissioned by someone wanting something special, there are not a lot of "stock" designs.

His latest offering, Equinox 7, is a good example. Most of those who want to cruise offshore in a powerboat go for one of the many passagemakers now available. These generally have a bit of the trawler about them and almost always are mono-hulls.

Yet Hill's latest client wanted a 15-metre powercat that could not only safely cross the oceans but do so very economically as well. In fact his design brief insisted on a vessel that could cruise at 20 knots for 1000 nautical miles.

Now that, as they say on the sports fields, is a big ask. Hill quickly realised that such a vessel would require "a whole new approach". Most of his renowned power catamaran designs were based around planing hulls but that obviously wasn't going to work here.

Instead, he chose a semi displacement shape and then ensured it was going to meet the owner's requirements by having his calculations subjected to a full CFD analysis at the MARIN Institute in Holland. This not only confirmed that he was on the right track, but also provided pointers for engine selection and range calculations.

The institute also had an interesting suggestion for Hill: try a "wedge" in the aft end of the prop tunnel.

"On a similar semi displacement cat that was finished before this boat was launched, we left the wedge out of the tunnel to start with," he explains. "We then fitted one after the initial sea trials and found it improved the performance a little.

"This time we built a wedge into the Equinox tunnels before it was launched."

Equinox 7's hulls are also fitted with full-length skeg/keels, which allow the boat to dry out on a hard stand, ramp or beach. They also provide added protection to the props and rudders when running in shallow water. Hill says the longer skeg does not affect the vessel's manoeuvrability and adds to its natural straight line tracking ability.

Although prop tunnels are not necessary on a semi displacement hull, they do reduce the draft and make it easier to fit protection. An added benefit is a reduction in buoyancy aft. This allows the engines to be placed further forward than would be the case with planing hulls.

Hill says this hull form is designed to perform most efficiently in the 15-to-20-knot cruising speed band.

"It also has very good economy at less than 15 knots, meaning a very good cruising range, especially as the standard 5200-litre capacity has been extended by an extra 1600 litres."

Equinox 7 is powered by Caterpillar 3126 engines. These consume a total of around 120 litres an hour at 20 knots. Allowing for a 10 per cent fuel reserve, this gives Equinox a range of close to 800 nautical miles.

Hill says the boat also has a "sweet spot": about 18 knots at 2200rpm. At this, consumption is just 90 litres an hour, or five litres per nautical mile, giving a range of 931 nautical miles with that 10 per cent reserve.

On a recent run, on mirror-smooth waters in the Bay of Islands, the catamaran recorded a flat-out speed of 24.2 knots at 2865rpm.

Catamarans, especially ones with an LOA of just 15.2 metres, might not often be seen cruising the world's oceans. Yet Equinox's owner need have no worry about her ability to stand up to the trials of passagemaking. Her construction is full foam cored composite, meaning she is both tough and rigid while also weighing in at just 24 tonnes in fully loaded mode.

It is not just Equinox's hull form that stands out from the ordinary. This ocean-going cat has some quite "different" features on board, too.

As is the case on most twin-hulled vessels, the accommodation has been consigned to the outer reaches: the hulls. This sensibly leaves the large open deck area for the important parts of boating: eating, drinking and entertaining. And, with an almost 6m beam, there is no shortage of space.

Hill has gone for a split-level approach with the helm station and a proper dinette (with seating for six or seven) on the raised level forward and the galley and casual settee seating a step or two down. The galley has been placed aft so that it services both the saloon and the cockpit (through opening servery-style windows).

There is also a handy door direct to the sidedecks, ideal for berthing, anchoring or coming alongside.

Hill clearly has something of a penchant for split-level living areas as he has created another one out in the cockpit. With all the conveniences below decks in the side hulls, a day head at the front of the cockpit is likely to prove very handy. So is the rather interesting island station with its barbecue, freezer and two-person settee. It is an unusual arrangement but clearly one that works as Hill has installed another settee on its back, facing aft.

The standard accommodation for large cats like this is a brace of cabins in each hull and Equinox is not much of an exception. She has three cabins and a service area, the latter, aft in the starboard hull, contains a washing machine and dryer and a genset.

The owner's cabin, forward in the starboard hull, is surprisingly spacious. This one features an athwartships island berth with steps either side for ease of access and the headroom is generous.

Pilothouse Powercat

LOA: 15.2 metres

LOH: 15 metres

LWL: 13.69 metres

Beam: 5.9 metres

Draft: 1.05 metres

Displacement: 19 tonnes (Light ship)

Construction: Foam core & E Glass laminates

Engines: 2 x Caterpillar 3126 @450mhp

Max speed: 24.5 knots

Cruise speed: 18 knots

Fuel capacity: 5200 litres (Std) + 1600 litres (long range)

Water capacity: 1000 litres

Priced from: $2.5m