When news of Joe Vittoria’s plans to build a 246ft (75m) sloop with a 300ft (91m) carbon fibre mast permeated the superyacht industry there were those who said it simply couldn’t be done. Mirabella V will be the biggest sloop in the world by far when she is launched in August 2003 but observers are still trying to get their heads round her amazing vital statistics and the fact that almost every fitting will have to be custom-designed and built. And as for that mast – well, 300ft of carbon? It’s impossible, said some pundits.

Everything including captive winches, which can pull 40 tonnes, a 1.5 tonne mainsail with 85ft (26m) battens, 15 tonnes of 76mm (3in) thick rod rigging, a 150-tonne lifting keel and the composite hull itself, will challenge accepted wisdom to handle loads and stresses never before experienced in a single-masted sailing yacht. The mast step alone is designed to withstand 1,500 tonnes.

‘M5’ technology
Some suppliers have invested seven-figure sums just to accommodate M5 technology, as it is now known, and any company in the superyacht arena worth its salt has been determined to secure a slice of the action.

Tabloid-style superlatives have been flowing thick and fast from this gargantuan project. Mirabella’s keel weighs as much as 100 family saloon cars; from truck to keel she is twice as high as Nelson’s Column in London and the hull is six times longer than the Editor’s 42ft yacht Firefly; you could park several double-decker buses inside the hull and the next tallest mast in the world doesn’t even come close at 213ft (65m). J Class yachts will be dwarfed by this monster.

But from a technical point of view, Mirabella is pushing out design boundaries and redefining the superyacht. So how are designer Ron Holland, structural engineers High Modulus and builders Vosper Thornycroft tackling the prospect of creating the biggest sloop the world has ever seen? And why does someone need a yacht this big?

At 246ft 8in (75.2m) LOA Mirabella V is not just the biggest sloop ever built but the biggest by a considerable margin. John Williams’s Georgia, designed by Paulu Scanu and Butch Dalrymple Smith and built in aluminium by Alloy Yachts in Auckland in 1999, is the next biggest at 159ft (48.4m) LOA and Jim Clark’s German Frers-designed Royal Huisman-built aluminium-hulled Hyperion at 155ft 6in (47.4m) was the biggest in 1998. The Dave Pedrick-designed Zeus at 150ft (45.7m), built in wood epoxy, was considered the biggest in 1994.

Even more extraordinary is Mirabella’s mast. The tube will be 285ft (86.8m) long but once cranes, aerials and other paraphernalia are mounted atop, the overall height will be very close to 300ft (91.44m) above the waterline. From keel tip to the top of the burgee staff she will measure 100m, or 328ft.

US$200,000 a week charter yacht
Mirabella’s vital statistics blow away all the ‘opposition’ and now stand seemingly unassailable in the ‘I’ve got the biggest one in the world’ stakes. And to do the whole thing in composites (of which more later) makes it even more audacious.
But there’s more to it than size and status.

This is a serious commercial undertaking and Vittoria is developing sail power for the floating high-performance five-star hotel business of the future, also known as luxury yacht charter. She will be available at US$200,000 per week for 14 guests.

Joe Vittoria, an American, returned to the USA in 1980 from the UK, where he had headed up Avis International, to become chairman and CEO of Avis Inc. In 1986 he organised the purchase of the company and their resale a year later, which put him in a position to buy his first superyacht. Vittoria is a very experienced yachtsman who has owned boats all his life, including a succession built by Camper & Nicholsons. He took delivery of his first yacht, a Nicholson 43, in 1971 and his success with a Nicholson 33 in 1974 introduced him to the talents of New Zealand designer Ron Holland.

But his first really large yacht was the 131ft (40m) Bruce Farr/Pekka Koskenkyla-designed Mirabella C launched in 1992 followed by the 134ft 6in (41m) Mirabella C III two years later. They were famously towed across a beach in Thailand by a team of elephants before being launched. Both were built in composites and both used project management and building expertise from the UK, including Paul Johnson’s knowledge.

Johnson is an ex-Camper & Nicholsons man and is Joe Vittoria’s representative and project manager for Mirabella V.
Together with Mike Carter at Vosper Thornycroft, he is masterminding this mega rubic-cube of a project. Paul Johnson told us, with a wry smile, that his last job was building the new Gosport ferry but quickly added that Victoria of Strathearn, Cyrano de Bergerac (both Camper & Nicholsons builds) Mirabella C III and Philanderer (similar to Mirabella and also built in Thailand), are also on his CV.

The Mirabellas were the biggest sloops of their time but their primary function was, and still is, to provide state of the art charter aboard a sailing boat. In addition to conventional tenders, Vittoria provides a twin-engined seaplane which flies guests to the charter yachts. This service will also be provided for Mirabella V’s 14 guests who will be accommodated in ultimate luxury in the yacht’s seven sleeping cabins.

Skydeck cinema
Motor yachts used to be the only serious option for chartering because they are fast, voluminous and easy to use. But the ease with which a sailing boat can now be handled, even one Mirabella V’s size, and the fact that this yacht is projected to sail at more than 20 knots and motor at 16, puts her into the big-time charter market alongside the seriously large motor yachts.
And Mirabella has the volume to accommodate everything from an open air ‘skydeck’ cinema and swimming pool to a gymnasium and sauna, three motor boats, wave runners, dive gear and 12 crew to pamper the guests. Another benefit is that sail as motive power has that low cost, added eco-value that no gas-guzzling, exhaust-emitting motor yacht can match. So for $200,000 a week she’s all yours.

Like ants in a pudding basin
The other question which exercises Vittoria’s mind is, just how big can you go with sail? In terms of the hull, one visit to Vosper Thornycroft’s extraordinary FRP (fibre-reinforced plastic) facility in Woolston, lying in the shadow of the Itchen Bridge near Southampton, will convince any sceptic that this is a project very much within the builders’ ability. Their experience in building FRP mine hunters and their large multi-skilled workforce mean they can take the M5 project in their stride.

Stand on the sheer line of the vast hull mould and I guarantee you’ll get vertigo as you look down into the amphitheatre of her hull. Workmen laying up the glass and positioning the foam core look like ants in a pudding basin. The place is almost clinically clean, organised and library quiet, quite unlike any steel or alloy fabricating plant. In fact, unlike any boatbuilding yard.

Vosper Thornycroft are more used to working with navies than ex-car rental bosses and in 30 years have built 270 ships for 34 countries. Frigates, patrol boats and mine hunters are their business. But VT’s unique selling point is their experience with FRP, which they first used for building Mine Counter Measure vessels when wood as a hull building material was no longer viable. Mike Carter recalled that the MOD originally insisted that FRP frames had to be fastened to the hull shells with thousands of metals bolts (‘just in case’), each bolt tested and bedded in with special cotton.

But the introduction of ‘compliant’ resins and the design of the 52m Sandown Class mine hunter, which was dramatically (and successfully) tested for strength by exploding a massive mine just yards from the hull, signalled a major leap forward in FRP technology. They built 12 Sandown Class mine hunters and to do it they erected four vast building halls in which parts of Mirabella are now taking shape.
“We’ve built train carriage roofs, pedestrian footbridges and special FRP protection for valves in the offshore oil industry post the Alpha Piper disaster but this is the first sailing yacht any of us can remember,” said Mike Carter. Even so, VT have had to extend their yard by 40ft (12m) to accommodate Mirabella’s enormous hull mould.

A gigantic scaffold supports the mould which is shaped by laser-cut MDF (medium density fibre) forms bolted to the framework every two or three feet. Thin sheets of MDF are laid over the forms and the mould is then fared. “That’s one thing VT aren’t used to – mine hunters could have lumps and bumps but this finish has to be perfect,” said Carter.

Julian Smith of High Modulus, the company responsible for the structural engineering, explained that there is nothing unconventional about the lay-up of the hull shell which accounts for more than 100 tonnes of the yacht’s overall predicted 750 tonnes. The outer skin of Mirabella is just 7mm thick (out of a total hull thickness of just 2.5in/63mm) and is made of layers of Kevlar and stitched bi-axial mat which absorbs resin well and helps prevent show through of the mat.

Polyester resins are used through the hull mould and the whole thing is laid up by hand. Then a layer of Herex foam is vacuum-bagged to the outer skin before the inner skin is applied. A vacuum-assisted resin injection technique is used once the foam has been baked to stabilise the gases in its structure. Carbon capping is used in ringframes and stringers for stiffness.

Another ‘plastic fantastic’
Smith’s structural engineering background is interesting. He made a famous breakthrough with the New Zealand ‘plastic fantastic’ 12-metres KZ 3,5 and 7 for the 1987 Fremantle America’s Cup and then went on to engineer Michael Fay’s extraordinary rule-busting winged K boat for the 88/87 Cup match against the Stars & Stripes catamaran.

He explained that Mirabella’s unusually low length to depth ratio has meant careful studies into how the structure might bend. As a result the deck mould is constructed of carbon fibre and foam to provide a stiff and relatively light structure which acts as a sort of strongback for the hull. Ironically, once complete it will have to be cut into five pieces so that it can manoeuvred out of one shed and into another before being bonded to the hull some time in July.

According to Ron Holland, the decision to go down the composite route (as opposed to alloy) was driven entirely by the owner. “Essentially he wanted a modern yacht and he’s been used to composite yachts. We save about ten per cent in weight over an alloy boat,” said Holland but the MCA requirements for fire insulation have nullified any major weight saving.

Because Mirabella weighs more than 500 tons and is more than 50m LOA, her safety requirements are like those of a ship. “We had to match the fire resistance of insulated metal which meant adding 40 tons of material to the composite surfaces,” said Ron Holland.
Interestingly, VT’s own tests showed that the glass in composite provided remarkably good heat resistance. In addition Mirabella will be fitted with a three-stage water mist fire-fighting system fed by a distilled water tank – distilled water if free of particles which would clog the misting system. Sea water can also be pumped for fire fighting.

That rig
Halmatic in Portchester, near Portsmouth, now owned by VT, will be building the 285ft (87m) carbon fibre mast and 85ft (25m) boom. “It’s really a whisper of a mast,” said Paul Johnson, referring to its surprisingly short chord length of about 4ft (1.25m) and a width of 2ft (0.6m). “It’s technology we’ve used before,” he added.

The spar will be built in at least three sections, one full length half and then the other half split into lengths, the top one of which will be tapered. Openings in the tube will be engineered into the carbon fibre matrix and once the internal fittings are in place the three pieces will be glued together. The entire rig, including standing and running rigging will weigh 35 tonnes.

At one stage ‘textile’ rigging like PBO and similar synthetic materials was considered but, despite the weight saving, it was felt that the technology was not far enough advanced to be applied to such a massive mast and that twisting and friction on the furling stays could pose problems. So Ocean Yacht Systems of Christchurch got the job to provide the longest rod rigging sections ever made. The forestay alone is 295ft (90m) long.

VT and OYS, who have installed new head pressing equipment to form the rigging ends, even studied the effects of thermal expansion on stainless steel rod to see if would cause problems in the Tropics but the changes were negligible. The standing rigging alone weighs 15 tonnes and the V1 is 3in (76mm) in diameter.

So that individual rod sections can be serviced and even removed from the rig without the mast being unstepped, a special pin and toggle system attached to moulded carbon fibre spreader tangs has been designed. Conventional terminal cups would have weighed more than 100kg (220lb) each (that’s ten for the five sets of spreaders) so there’s also a weight saving issue.

The boom is 6ft 6in (2m) wide at the mid-point. It’s a Park Avenue shape with troughs either side of a central spine designed to take the six full-length mainsail battens, the longest of which is 85ft. Harken batten cars will be used on the mainsail track and a specially designed series of track ‘sidings’, sending cars either side of the mast, will be used so that the main stack can be reduced to a manageable height above the gooseneck. Reefing is of the slab variety.

The Doyle main will be built of Vectran and weigh about 1.4 tonnes. There’s a remarkable amount of roach now designed into the head of the sail and, not unlike the modern Open classes, Mirabella will have to drop her main to tack. In practice, she will sail most of the time in the working position with one reef in. A hydraulic halyard lock with full hoist and reefing positions will be fitted and to reduce weight and compression loads, headsails will be lashed in position and halyards removed once they are hoisted.

There are three stays forward, one for a Cuben Fibre reacher which can be used in winds of up to 18 knots apparent, another for a working jib and an inner forestay or baby stay on which a storm sail (specified by MCA) can be set. There’s no trysail but the storm jib can be set in 50 knots apparent.

One of the biggest challenges for Peter Powell, who is in charge of sourcing the hydraulic winch systems, has been finding units able to cope with the massive sheet loads which at times could be in excess of 38 tons.

Mirabella V is designed to sail efficiently at a maximum angle of heel of 15°. Above this angle sheet loads start to become excessive. The biggest automatic captive winches on board will be able to pull 38 tons but if the yacht reaches a heeled angle of 20° the winches will automatically start paying out to reduce loads.

Mirabella should be able to sail comfortably at well over 20 knots in wind speeds of about 15 knots. Like a modern multihull, though, the apparent wind angle will be pulled forward and Mirabella’s skipper will have to compensate for this effect in sail trim and sail area.
The M5 team have abandoned any thoughts of an asymmetric and will instead use the vast Cuben Fibre genoa for light wind sailing. Despite its size, it weighs only 300kg. A big advantage is the small diameter of the furl once stowed – Vectran would have measured more than 2ft (0.6m) in diameter but Cuben reduced this to about 1ft (0.3m).The working jib is set on a separate inner forestay and will be made of Vectran.

The yacht will be fitted with captive winches from the German firm Egon Saunders. The winches are designed in two parts, the pulling element and a line storage drum. An advantage is that the storage drum can fitted in a less space sensitive area, away from the business end of the winch.

Under power Mirabella’s twin 1100hp MTU diesels and variable pitch propellers will give her a top speed of 16 knots.
Perhaps the biggest engineering challenge of all is Mirabella’s 150-ton lifting keel which will reduce draught from 31ft to 12ft 9in (9.5m/4m). Intentionally, the yacht’s minimum draught is the same as that of Vittoria’s previous Mirabellas, enabling him to visit his favourite anchorages, despite being in a yacht more than 100ft longer.

The steel fin weighs 26 tonnes and is attached to a fabricated bulb which specialist keel-maker Henry Irons of Wadebridge in Cornwall will fill with more than 100 tons of molten lead. The entire structure will be moved by a giant hydraulic ram with a stroke of 33ft (10m) powered by two dedicated 15kW motors.

Here comes the hyperyacht
For a yacht of her size, her two-year build time is remarkably short but Vosper Thornycroft appear to be ahead of the game with their specialist knowledge, multi-skilled local workforce and custom-built building facility. Being able to construct so many large components at once, including the vast amount of interior furniture being fabricated by locally based Nicholson Interiors, means that the speed of the project has been dramatically increased.

Vosper Thornycroft have already been approached with enquiries for other vessels and it was interesting to note that the mould framework can be adjusted to accommodate even larger yachts. Could this herald a new era of the hyperyacht?