Yacht design continues to advance quickly, as evidenced by the leap in performance made by the current generation of IMOCA 60s compared to just four years previously. The same is true among cruising designs and the Nautitech 48 Open also represents a big step forward, with hull shapes refined compared to those of the Nautitech 44 that was launched only three years ago. This simultaneously boosts performance while also improving handling and safety.

One of the key design aims was to improve performance at typical moderate sailing speeds of around 8 knots, which was achieved by modifying the rocker profile of the bottom of the hull, especially towards the transom. At the same time the bows are 10cm above the static loaded waterline, which helps the boat to turn more easily, both at sea and when manoeuvring in harbour. High aspect ratio rudders mounted almost right aft also help in this respect.

This boat has a very direct feel to the helm and in many ways it’s more like a monohull to steer, even if the difference that small tweaks to sail trim make is not as easy to notice. It’s also notable that very little speed is lost in tacks and in this respect the boat handles more like a good monohull than a traditional catamaran with immersed forefoots.

In fact, spinning the boat as quickly as possible in a tack is the best option, even if that feels counterintuitive, especially to a yacht sailor. When executed neatly boat speed drops remarkably little.

The aft helm positions and open concept also make steering a much more sociable occupation than with a raised helm position. The downsides are that these positions lack protection and visibility is not as good, particularly past the coachroof. In one sense this is little different to a monohull with a blind spot under the jib, but can take some getting used to and even then will never have universal appeal.

Still, it should be no surprise that the Nautitech 48 Open has potential to maintain high average speeds on passage. In 12 knots of true breeze, with a 125m2 furling gennaker set, we made just over 10.5 knots with the true wind just aft of the beam, and 9 knots in slightly more breeze but deeper angles between 110° and 120°.

Performance dipped slightly to 7 knots when the true wind dropped to 10 knots. This was with the Code 0, rather than an asymmetric spinnaker, all of which points to easy 200-plus mile days when on passage.

Design secrets

Another design aim for the Nautitech 48 Open was to improve both handling and safety by inducing the bows to lift further at higher speeds. This reduces the chances of burying a bow when sailing downwind in boisterous conditions, which in turn reduces any tendency for the bows to steer the boat into a broach.

This additional lift is mostly achieved by tweaking the rocker shape of the underside of the hull towards the transoms, with a little help from U-shaped underwater sections near the bow. Lionel Huetz of the Marc Lombard Yacht Design Group told me neither of these changes are extreme, so the modified bow shape doesn’t promote slamming in a head sea, while drag at the transom that would put a brake on acceleration is not increased at moderate speeds.

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“What we’ve done is a combination of starting with the bows slightly raised,” Huetz told me, “which means the hull shape doesn’t need to generate a lot of lift. Aft of that the key is to have the correct rocker shape underneath, but without adding too much rocker, because that adds drag at medium speeds and stops the boat accelerating.”

The result of these changes is that turbulence at the transoms of the Nautitech 48 Open disappears at speeds over 10 knots, when the stern wave is left behind in a manner that has similarities to a monohull planing.

Frustratingly, we didn’t have enough wind to see this under sail, but in light airs and the twin 75hp Volvo Penta diesel engines running at 3,100rpm we made an impressive 11.3 knots of boat speed. At that speed the stern wave was well behind the boat and the front metre of each hull airborne, with the bows roughly 30cm above the water. This will clearly be advantageous when sailing downwind VMG angles in a big breeze.

At the other end of the scale, performance in very light airs has long been an excellent test of a thoroughbred design. Our test boat had an 89m2 Code 0 designed for tight sheeting angles and upwind use, allowing us to sail at apparent wind angles of 30° in 3-6 knots of true breeze. Impressively for a boat with a light displacement of 13.5 tonnes, our boat speed almost equalled the true wind speed in these conditions, and the helm still retained its very precise feel.

The test Nautitech 48 Open also had a very high aspect ratio self-tacking jib, which makes for wonderfully easy handling.

A more efficient 64m2 overlapping sail is offered as an option, which might reduce the need to carry the upwind Code 0, leaving a furling gennaker, plus an 18m2 asymmetric spinnaker handled with a sock, as options that would give an efficient all-round sail inventory without having to carry too many individual sails.

Huetz also says the overlapping headsails give a perfect sail plan downwind in a big breeze when combined with two reefs in the main.

Safe speeds

During initial sea trials off the Atlantic coast of France, the first Nautitech 48 Open notched up 20 knots boat speed sailing at a 120° true wind angle and 20-25 knots of breeze in 4m waves. I’m told the boat was very easy to steer, even using the pilot, but still with the option to play the waves and have a lot of fun.

This may sound alarming to those accustomed to a more sedate pace while cruising, but a 120° true wind angle gives lots of scope to bear away and massively reduce the apparent wind speed, thereby calming everything down if necessary.

Equally, heel stability increases with the fourth power of the size of a boat and becomes enormous once a catamaran reaches this length, so risk of capsize is a fraction of that of a 40ft boat in similar conditions. Indeed, this effect is so marked Huetz tells me that above 50ft it’s routine not to engineer the masts of cruising catamarans to take the full rig loads that would be needed to capsize the vessel, as to do so would require an unfeasibly heavy and cumbersome spar.

The design team also analysed the likely benefits of daggerboards for this boat, instead of the relatively deep fixed keels that have been fitted to Nautitechs to date. They concluded that, when compared to efficient keels with a proper aerofoil cross-section, the benefits of daggerboards were too marginal to be worth the extra build cost, loss of interior space and added complexity when tacking and gybing.

Deeper keels than usual for a catamaran of this size also allows for more efficient higher aspect ratio rudders, which has a direct impact on the feel of the helm. Steering is by cable, with the pilot directly attached to the port quadrant, so it’s available immediately for steering in the event of cable failure.

There’s also an option for a second pilot system on a completely separate network for redundancy – an important factor for those who intend to sail long distances.

Sail handling mostly takes place just inboard of the helm stations, which works well in most respects, although there’s not a direct line of sight between someone working centrally on the foredeck and another in the cockpit, for instance when hoisting a Code sail or spinnaker.

A second drawback is that lines turn through two 90º angles before reaching the clutches and winches working areas, which increases loads and friction. The mainsheet traveller runs across the beam aft of the cockpit and was easily controlled by a Harken electric Flatwinder system on our test boat, while the gennaker and asymmetric spinnaker sheet to each quarter.

We sailed with seven on board the Nautitech 48 Open, yet circulation of people around the saloon and cockpit areas generally proved to be very easy, with plenty of space for two or more to pass each other easily. The only exception is at the very aft end of the cockpit, where there’s little space to pass and this is also an area in which you’re working lines or steering… and changing sides in tacks and gybes.

Of course this isn’t an issue on semi-flybridge catamarans, or those with a raised helm station further forward, from which almost all sail handling can be carried out, though the Nautitech’s twin aft helm stations have other advantages.

Although little more than a decade old, Nautitech was one of the pioneers of what it calls the Open concept of blended indoor/outdoor living. This is now well established and offers a big improvement compared to older models, though while there’s a wide opening between the cockpit and saloon it’s not possible to connect the tables in two different areas together.

The Nautitech 48 Open cockpit table is offset to starboard and has a folding leaf in the middle to convert it from coffee table mode to full dining. There’s also a further seating area on the foredeck, which opens up more options for socialising space, or for added privacy when berthed stern-to.

Views all around

The saloon has almost 360° vision that’s interrupted only on each quarter and benefits from plenty of light, space and natural ventilation. The yard has also worked hard to reduce solar gain here and therefore keep it cooler in bright sun. So there are fewer big glazed panels overhead, while optional covers are available to keep sun off the windows. There are also opening hatches in the coachroof, plus a couple in the forward windows to maximise natural ventilation.

To starboard is a big, well-appointed galley with ample worktop space and good stowage, plus an extensive choice of refrigeration and freezer options. Seating and the saloon table are to port, with room for six people and enough for eight at a pinch. However, as mentioned, the saloon and cockpit tables can’t be connected together to accommodate a larger party.

The Nautitech 48 Open has a great forward-facing navigation area and watch-keeping station, while the bar-style feature at the front of the saloon that was first introduced on the 44 is a neat addition adding worktop/table space and creating a further small socialising area.

This may sound like a lot to pack into one area, even on a multihull the size of the Nautitech 48 Open, but the layout is well executed and there’s still plenty of space to move around, so it doesn’t feel cluttered.

In addition, attention to detail is impressive, both in the way the interior is put together and in items like the solid capping pieces on the joinery that will absorb knocks and bumps as the boat ages without damaging more fragile veneers.

Nautitech can accommodate a degree of flexibility on the layout in each hull, for instance in the number and configuration of the heads and shower compartments. The Nautitech 48 Open we sailed is an owner’s version with a very large forward heads area in the port hull, including room for his and hers basins, a separate shower cubicle, space for a washer-dryer and decent stowage. There’s also a dressing table with a section that pulls out to create a desk that has an outside view through the hull windows.

The test Nautitech 48 Open’s starboard hull is configured with a smallish double cabin aft and Nautitech’s so-called SmartRoom. This is a flexible concept that can be fitted out as a utility, workshop and stowage area, albeit with occasional berths.

On this boat it was set up with a settee/single berth and a small desk area with a view out through the hull window, but can be quickly converted into a double bed and there’s an additional bunk bed that swings out above it. Three children, for example, could sleep in that space if you had visitors. This hull also has large separate shower and separate toilet compartments, although the boat can be configured with up to four heads, or with a larger aft cabin.

Another important element of this boat’s performance is its relatively light displacement. Structural mouldings are vacuum infused, with a Divinycell foam core, while bulkheads are glued and bonded at key locations. There are four watertight bulkheads giving the boat a good chance of remaining afloat, even in the event of extreme damage.

Our test Nautitech 48 Open was equipped with 2kW of solar panels allied to a 1,020Ah 12V battery bank, a €40,000 option that all of the eight boats sold to date have taken. Roughly half have also specified a diesel generator, but that’s only essential if air conditioning is also specified, which is rarely chosen by those who intend to sail long distances.

At 300lt each the fuel tanks are of a reasonable size for long-distance sailing and spending extended periods on board, especially given the boat’s performance in light airs, and the solar/ lithium options that should all but eliminate the need to use diesel power for battery charging.

Systems appear to be very neatly installed, with easy access to pumps and filters, while all interior trim panels are clipped in place to give instant access to wiring, deck fittings and so on. The wiring of the test boat looked very neatly installed and the digital switching system has a full manual backup.

Nautitech 48 Open specifications

LOA: 14.67m 48ft 1in
LWL: 14.32m 47ft 0in
Beam: 7.97m 26ft 2in
Draught: 1.55m 5ft 1in
Displacement: 13,500kg 29,768lb
Mainsail: 93m2 1,001ft2
Self-tacking jib: 42.5m2 455ft2
Genoa (optional): 64m2 688ft2
Code 0 (optional): 89m2 958ft2
Gennaker (optional): 125m2 1,345ft2
Spinnaker (optional): 175m2 1,883ft2
Engine: 2 x D2-60 Volvo saildrive
Diesel: 600lt 132gal
Fresh water: 600lt 132gal
Air draught: (ex antennas) 23m 75ft 6in
Naval architect: Marc Lombard Yacht Design Group
Interior design: Christophe Chedal-Anglay
Base price: €999,800 ex VAT; Price as tested: €1,133,521
Builder: nautitechcatamarans.com

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