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Modernizing the Free-Standing Rig

According to the designer Eric Sponberg, the new rig should deliver 25 percent more power.
Dr. Blake Cady and his sailing buddy Rob DeVries arrived at Concordia Yachts in Padanaram Village, MA, early one cold Saturday morning in December. It was time to begin the work of rigging the brand-new, carbon-fiber, rotating wingmasts on his Freedom 38 cat-ketch Woebegon Daze. The pair came with the tools needed for their first task: brushes, a broom, and a shovel to clear away the snow that had fallen during the night.

Rigging day had been a long time coming. Delays had pushed back the delivery of the rig from April to mid-December. Even so, the clear, sunny day with its freshening breeze promised good sailing conditions—if the rigging could be completed in time. But it wasn't until the end of the day, with the full moon rising over the rooftops of this coastal village, that the sails were finally raised. The rotating wingmasts turned their leading edges into the wind, the sails filled with the breeze and the bronze colors of the setting sun, and the work of tuning the rig continued as the boat strained at its dock lines.

After many months of waiting, Dr. Cady would need to wait a little longer to see how his new rig handled. And there was just one more week left before the insurance coverage for the season ended.

His patience would be well rewarded. He now had one of the most efficient sailing rigs in the world. "I like to do innovative things," he said. "This will make an airfoil of the mast, and eliminate the turbulence you get with a round mast," he explained.

"This rig design represents my next-generation thinking," said Sponberg, a Newport, RI-based naval architect. He believes that only the rig on the mega-catamaran Team Philips comes close to his design in terms of innovation."

In addition to the rotating wingmasts, the rig's designer, Eric Sponberg, had designed a wishbone boom vang that may be unique. "This rig design represents my next-generation thinking," said Sponberg, a Newport, RI-based naval architect. He believes that only the rig on the mega-catamaran Team Philips comes close to his design in terms of innovation.

The rig should deliver 25 percent more power, according to Sponberg. Because there are no stays or shrouds, the sails have a full roach, and the boom can swing forward of the beam. Sponberg claims that drag is reduced significantly because the leading edge of the masts always face into the wind, and the elliptical shape of the sails is more efficient than a triangular shape. These changes mean Wobegon Daze will "get pure lift, many times more powerful than drag," said Sponberg, and "can sail fast dead downwind" with little chance of broaching.

The wishbone booms and boomvang create an arrangement enabling optimal sail trim.
The unusual wishbone/boom-vang arrangement, with the vang built into the boom, was designed to prevent an expensive problem that plagued Project Amazon, a similar Sponberg design that saw limited action in the 1998 Around Alone race. When the wishbone boom on Project Amazon's main mast swung outboard, the angle of the boom to the deck became too acute and the force "exploded $5,000 worth of sheet blocks like toys," said Sponberg.

Project Amazon is a 60-foot aluminum cat-ketch with rotating carbon-fiber wingmasts. The boat' s name reflects its owner's source of wealth: gold, extracted with ecologically friendly technology from ancient riverbeds on the slopes of the Andes. Project Amazon's owner Sebastian Reidl, had to abandon the race when the keel, where the fuel was stored, developed a leak. Repairs couldn't be made in time to continue because the owner's fortunes had plummeted with the gold market that year. A new owner hopes to enter the boat in the upcoming Around Alone in 2002.

Sponberg has worked with carbon-fiber masts and cat-ketches throughout his career. Carbon-fiber is twice as strong and 40 percent lighter than aluminum, he noted, and a carbon fiber, unstayed mast has far fewer parts than a conventional, stayed aluminum mast. In the case of Project Amazon, for example, only two parts—large bearings—were used to support the mast, compared to upwards of 500 parts needed for a conventional stayed rig. But because an unstayed mast needs to be larger than a stayed mast, the weight and cost of an unstayed carbon-fiber mast and of a conventional stayed mast are about the same.

The main drawback with carbon fiber masts, according to Sponberg, is that few manufacturers have the equipment to make them, and few have been designed. The custom design and manufacturing adds to the costs.

Rotating masts may also require some changes to other equipment. The radar, for example, may need to be mounted on a pole at the stern instead of on the mast, because the rotation of the mast will create some disorientation while using the radar. Similarly, any wind indicator mounted on top of the mast will need a centerline indicator. Orientation will also be a problem with any tricolor light atop the mast except when sails are down and the masts are lashed to the centerline; separate tricolor lights can be mounted on the pulpits to resolve this issue.

The mast fairings for Wobegon Daze (the outside shell of the mast) are hand-laid fiberglass using female molds from Project Amazon; the carbon-fiber tube inside the mast was made by a braiding machine over an aluminum tube that was removed after curing in an autoclave—a pressurized oven. The masts were manufactured  by Composite Engineering of Concord, MA.

Intrigued by Project Amazon, Dr. Cady began investigating how a similar rig might work for his own boat. He soon found a cat-ketch with rotating wingmasts made of wood-epoxy. The boat was up on Lake Ontario, and Dr. Cady was invited up for a sail. Convinced that the rig was more efficient than what he currently had, he commissioned Sponberg to work up a design for Wobegon Daze.

The two had worked together before on another modification of Wobegon Daze. The original Freedom design was a sloop, and when the manufacturer changed the rig to a cat-ketch, the main mast was above the bow overhang, causing it to nose-dive under sail. A new plumb bow designed by Sponberg solved that problem, and also increased the boat's speed by lengthening the waterline more than 12 percent.

Now they were working side by side on a bitterly cold day to assemble the pieces of the new rig.

The base of the mizzen mast is a fairly simple affair.
The piercing cold made work difficult, but Dr. Cady and his pal DeVries took the weather in stride. They've sailed Wobegon Daze together for years in the waters around Newfoundland, and wore their Newfie gear, including thermal underwear.

The wishbones and booms were toted from nearby sheds to the snow-covered dock, hoisted aboard, and fastened to the masts. About mid-morning, the sailmaker delivered the new sails. The owner of Concordia Yachts, Brodie MacGregor, arrived to help, along with one of his yardworkers. By mid-afternoon, one of the workers from the company that had fabricated the masts showed up with two friends and helped shift the boat around the finger pier so the bow was facing into the wind. The sail cars were then slipped onto their tracks, the headboards, tacks and clews were shackled, single-line reefing and lazy jack lines were fixed, and all lines were led back to the cockpit.

"The beauty of the cat-ketch rig," Dr. Cady noted in a rare idle moment, "is you don't have to mess with spinnakers and jibs." A cruiser at heart, although he's participated in two Marblehead-to-Halifax Races and one race to Bermuda, Dr. Cady said the only foresail he plans to use is a small mizzen staysail. The boat, however, is no slowpoke. It's hit 12 knots while surfing, and can regularly clock speeds of nine and 10 knots.

As the work progressed, faults were found—things that were not done, things that jammed, things that didn't look quite right. Numbed with cold, one of Dr. Cady's fingers slipped as he was fastening some bolts. The pristine white masts were baptized with drops of blood.

After tinkering with adjustments in the fading light, the crew mounted the snow-slippery ramp to shore and gathered to look at what they had done. It was a beautiful sight.

Freestanding, carbon-fiber masts benefit from not needing standard rigging, allowing full roach sails.
But soon the questions arose—was that wrinkle in the leech of the sail due to a jammed vang, or a poor cut of the sailcloth? Were the reefing lines crossed? The crew scooted back down the ramp and continued tuning the rig until darkness called an end to the day.

A week later, Dr. Cady was back. After working out a problem with the main vang, he cast off, and went sailing. The sail lasted two hours, covering the five miles to Wobegon Daze's winter berth at Fairhaven Shipyard, across from New Bedford.

"It was good," Dr. Cady said. "Everything worked well, and it moved well. I was pleased."

It was the last possible moment he could have sailed. The next day, a storm system would move in with gusts of more than 50 miles per hour, and the day after that, the insurance coverage would end.

Now, waiting for spring like other northern sailors, he has memories of that very last sail, with the wingmasts turning to cut through the air and the sails snapping into perfect shape, to carry him through the winter.

Rig Specifications

The new masts for Wobegon Daze, a Freedom 38 cat-ketch built in 1985, were made from the female molds for the top halves of Project Amazon's masts, which are nearly twice as long. The wing-shaped fiberglass shells enclose carbon-fiber tubes that fit over shorter carbon-fiber stub masts, which support the assembly and are stepped on the keel. Although stronger than aluminum, the fiberglass and carbon-fiber masts are brittle, and have very little flexibility. To compensate, Sponberg designed them to withstand up to two and a half times their maximum load, which would be sustained if the boat was heeling between 45 degrees and 60 degrees.The vang, built inside the boom, is attached to the mast with a gooseneck fitting. The wishbones are fastened higher up on the mast, with wire preventers to keep them from swinging out too far in relation to the turn of the masts. The masts themselves can rotate 360 degrees. The open ends of the wishbones are fastened to the ends of the booms. The vang has six inches of movement, and can leverage the ends of the wishbones up to 17 inches to control the shape of the sail. All lines are lead back to the cockpit.

Masts:    Hand-laid fiberglass over a carbon-fiber tube, constructed by Composite Engineering, Concord, MA.

Wishbone booms:    Custom 3 -inch aluminum tubes made by New England Boatworks, Portsmouth, RI.

Boom-vang:    Quik Vangs, built by Hall Spars of Bristol, RI, were supplied to New England Boatworks, who installed them inside the booms.

Sails:    Mainsail, mizzen sail, and staysail were made by Hood Sails, Middletown, RI.

Total cost:    About $92,000, including design, custom manufacturing, sails, and yard bill.

New Rig

Old Rig

Sail Area

919 square feet

682.19 square feet

Mast weight

300 pounds each

340 pounds each

Mast height (above deck)


43 feet, 7-7/8 inches

48 feet 6 inches


37 feet, 5-1/2 inches

34 feet 9 inches

Mast dimensions

21 inches wide by 10-1/2 inches thick (elliptical section, rotating)

9 inches, (round section, non-rotating)

For more information contact designer Eric Sponberg, Newport, P.O. Box 661, Newport, RI 02840, 401-849-7730.

Suggested Reading List

Finding Beauty in a Junk by Michelle Potter
Optimizing Downwind Sailing by John Kretschmer
Quick Rig and Deck Check by Tom Wood

SailNet's Buying Guide - Boom Vangs


Bruce Caldwell is offline  
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