Mirabella V, with its nearly 300-foot-tall mast, heads out of Portsmouth Harbor in England for engine trials last spring. The 246-foot, British-built yacht sports the world’s largest sails. Doyle Sailmakers cleared a series of engineering hurdles in designing and building the combined 42,651 square feet of material.
The mainsail for this dinghy, which was launched in December 2003 and first sailed in April 2004, encompasses 13,988 square feet. Compare this to one of the boats in the American Yacht Review section of this magazine, like Onora, a 62-foot Chuck Paine design. From Mirabella V’s mainsail, you could tailor 16 mains to fit Onora and still have 222 square feet left over for placemats (a formal meal for 20 can be served in the yacht’s “dining room”). Mirabella V’s UPS, or reacher, is so big, at 17,366 square feet, it is listed in Guinness Book of World Records as the world’s largest sail. Designing and building these sails was an engineering task more akin to crafting a suspension bridge than sewing a few square feet of Dacron. According to Doyle Sailmakers founder, Robbie Doyle, “One of the biggest challenges was getting all the detailed engineering organized so there would be no surprises when it came time to build the sails.” It was partly the Doyle team’s extensive and detailed proposal that swayed Mirabella V owner Joe Vittoria and the British builder Vosper Thornycroft. “The Thornycroft engineers were impressed with our engineering approach,” Doyle said. The Doyle team had to conquer four major problems associated with Mirabella V’s sails. The first was the cloth used to make them. “There’s no material in sailing that was available,” Doyle said. “That was a big challenge.” Laminate sails — where strips or pieces of material such as Vectran or Kevlar are glued between layers of film — while seemingly the lightest approach, actually turns out a sail that is too heavy. What was needed was an ultralight woven material. Since there was nothing like that on the market, Doyle, teamed with Warwick Mills, a special applications fabric mill in New Ipswich, N.H., designed and built its own, calling the new lightweight fabric OceanWeave. Combining a tightly woven, warp-oriented Vectran core with a specially woven taffeta, OceanWeave is a low-stretch, durable and lightweight sailcloth. “What’s amazing is how lightweight the material ended up,” Doyle said. And Doyle is not reserving OceanWeave to Mirabella V–sized boats; it is available in a variety of weights for boats from 45 feet on up. The next problem lay in the sheer size of the sails. The solution for the main was to construct it from seven panels, joined by hefty, full-length battens (the longest batten is 80 feet, long enough to be a mast for a 72-footer). This approach, called the Doyle Segmented Mainsail, made the main easier to build, transport and service (although, at 3,389 square feet for the largest section, these segments aren’t easier to deal with in the sense that most boatowners mean easier!).
Should the full batten of a 35-foot voyaging boat’s main get caught on a backstay when gybing, it’s an annoyance. But if the batten for a 246-foot boat gets caught on the backstay, it’s a major problem that could lead to batten failure, possibly worse. Doyle engineered around this by devising the Compression Spring Batten, which has a hydraulic spring at the mast end. This spring allows the batten to compress and slide past the backstay, saving the batten from breakage.
Finally, after you have made a huge sail, how do you control it? The standard approach is to build steel rings into the corners of the sail to attach sheets, halyards, outhauls, etc. However, when the sails are this big, this steel hardware becomes massive — and dangerous, both to the crew and to the rig itself. The solution was a technique Doyle had already devised, Soft Corners. This approach uses high-strength, low-stretch cordage fastened internally to the sail’s corner reinforcing. The strands of line are sewn into the sail’s patching in a radial pattern. This spreads out the high loads found at corner attachment points.
Besides preventing damage to the rig from steel fittings and reducing the danger of a flogging sail injuring a crewmember, there are weight savings in not using steel components. According to Doyle, a single reefing block for the main would have weighed 80 lbs. But the nylon bushing for this application weighs a modest 25 lbs.
The sails for Mirabella V are an impressive achievement. The technology employed to make these sails is paying off since, as of this writing, the boat is currently successfully sailing in the Mediterranean. With its powerful sails, and 246-foot-long hull, this superyacht has a theoretical hull speed of roughly 20 knots. One thought to ponder, though: at the end of a day of sailing, which lucky crewmember gets the job of flaking the main and bagging the headsails?
For those still wondering about the title of this piece, Brobdingnag was, like Lilliput, one of the worlds Gulliver experienced in his eponymous wanderings. While people and things in Lilliput were tiny and Gulliver a towering giant, in the land of Brobdingnag, a suddenly diminutive Gulliver found the situation very much reversed. n
Designing and building these sails was an engineering task more akin to crafting a suspension bridge than sewing a few square feet of Dacron. According to Doyle Sailmakers founder, Robbie Doyle, "One of the biggest challenges was getting all the detailed engineering organized so there would be no surprises when it came time to build the sails." It was partly the Doyle team's extensive and detailed proposal that swayed Mirabella V owner Joe Vittoria and the British builder Vosper Thornycroft. "The Thornycroft engineers were impressed with our engineering approach," Doyle said. The Doyle team had to conquer four major problems associated with Mirabella V's sails.
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The first was the cloth used to make them. "There's no material in sailing that was available," Doyle said. "That was a big challenge." Laminate sails &mdash where strips or pieces of material such as Vectran or Kevlar are glued between layers of film &mdash while seemingly the lightest approach, actually turns out a sail that is too heavy. What was needed was an ultralight woven material. Since there was nothing like that on the market, Doyle, teamed with Warwick Mills, a special applications fabric mill in New Ipswich, N.H., designed and built its own, calling the new lightweight fabric OceanWeave. Combining a tightly woven, warp-oriented Vectran core with a specially woven taffeta, OceanWeave is a low-stretch, durable and lightweight sailcloth. "What's amazing is how lightweight the material ended up," Doyle said. And Doyle is not reserving OceanWeave to Mirabella V-sized boats; it is available in a variety of weights for boats from 45 feet on up.
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The next problem lay in the sheer size of the sails. The solution for the main was to construct it from seven panels, joined by hefty, full-length battens (the longest batten is 80 feet, long enough to be a mast for a 72-footer). This approach, called the Doyle Segmented Mainsail, made the main easier to build, transport and service (although, at 3,389 square feet for the largest section, these segments aren't easier to deal with in the sense that most boatowners mean easier!).
Should the full batten of a 35-foot voyaging boat's main get caught on a backstay when gybing, it's an annoyance. But if the batten for a 246-foot boat gets caught on the backstay, it's a major problem that could lead to batten failure, possibly worse. Doyle engineered around this by devising the Compression Spring Batten, which has a hydraulic spring at the mast end. This spring allows the batten to compress and slide past the backstay, saving the batten from breakage.
Finally, after you have made a huge sail, how do you control it? The standard approach is to build steel rings into the corners of the sail to attach sheets, halyards, outhauls, etc. However, when the sails are this big, this steel hardware becomes massive &mdash and dangerous, both to the crew and to the rig itself. The solution was a technique Doyle had already devised, Soft Corners. This approach uses high-strength, low-stretch cordage fastened internally to the sail's corner reinforcing. The strands of line are sewn into the sail's patching in a radial pattern. This spreads out the high loads found at corner attachment points.
Besides preventing damage to the rig from steel fittings and reducing the danger of a flogging sail injuring a crewmember, there are weight savings in not using steel components. According to Doyle, a single reefing block for the main would have weighed 80 lbs. But the nylon bushing for this application weighs a modest 25 lbs.
The sails for Mirabella V are an impressive achievement. The technology employed to make these sails is paying off since, as of this writing, the boat is currently successfully sailing in the Mediterranean. With its powerful sails, and 246-foot-long hull, this superyacht has a theoretical hull speed of roughly 20 knots. One thought to ponder, though: at the end of a day of sailing, which lucky crewmember gets the job of flaking the main and bagging the headsails?
For those still wondering about
the title of this piece, Brobdingnag was, like Lilliput, one of the worlds Gulliver experienced in his eponymous wanderings. While people and things in Lilliput were tiny and Gulliver a towering giant, in the land of Brobdingnag, a suddenly diminutive Gulliver found the situation very much reversed. n
