Open 60 design trends not for voyaging boats

The abandonment of five yachts and the death of Gerry Roufs during the recent Vendee Globe around-the-world event has focused worldwide attention on the hazards of contemporary offshore racing in much the same way the Fastnet disaster did in 1979. The fact that the super-wide, lightweight open class 60s are prone to capsize and to remain inverted should certainly come as no surprise. These boats are designed to a permissive rule that encourages wide beam, permits unlimited sail area, and does nothing to ensure positive stability at heel angles beyond 90°.

Open class 60s, in fact, have evolved with most of the characteristics of racing multihulls, including very high inverted stability. Certainly it’s unlikely that these extreme monohulls are anywhere near as foolproof (or as safe) as the average offshore voyaging multihull, especially considering that an unballasted multihull is virtually immune to sinking.

Of particular interest is the fact that some voyaging yacht designs are following BOC/Vendee trends. The idea is that the technology that enables a solo racer to reel off 200 to 300 miles per day will make offshore passage-making easier and more pleasurable for the typical voyaging couple. Certainly many modern developments such as low-friction sailing control systems, advanced roller furling, “smart” autopilots, computerized navigation, and real-time weather data access have proven their worth in both solo racing and shorthanded voyaging. But unless the linked problems of capsize and high inverted stability are resolved satisfactorily, most voyaging sailors will probably want to think pretty hard before going very far down the wider-and-lighter road. The majority of voyaging yacht designers still favor a conservative approach, so in most cases the “fast passage-makers” on the market are moderately narrow boats with light rather than ultra-light displacement.

Water ballast can dramatically boost sail carrying power while boosting displacement to help punch through head seas. On the debit side, though, the ballast tanks eat up valuable interior space, and loading up with a ton or two of icy sea water can put a distinct chill on the atmosphere of the salon. Canting keels are even less conventional, but unlike water ballast they work almost equally well with either wide or narrow boats. On the other hand, its difficult to engineer and maintain a swing keel system, and the loss of keels (albeit conventional ones) has been occurring with sobering frequency of late. All the same, canting keels are “hot” right now, much as winged keels took flight soon after the Australia II won the ’83 America’s Cup. This spring, the famous 65-foot Merlingrandaddy of all West Coast ULDBs with a beam of barely 12 feethas been retrofitted with a canting keel to stiffen her up and is currently in hot pursuit of yet another TransPac record.

The concept of a slim yet very stable hull that is easily driven by a small, highly efficient rig has been making the rounds for more than 100 years. It’s just that now, thanks to superior boatbuilding materials and developments such as moveable ballast, we can get a lot closer to the dream than ever before. But as I see it, the open class 50s and 60s have headed off on an evolutionary tangent that’s resulted in some extremely fast but ultimately less-than-seaworthy offshore craft. Now it remains to be seen whether race organizers will legislate a shift toward more wholesome designs before the September ’98 start of the Around-Alone Race (formerly known as the BOC Challenge).

Open class rules

The basic parameters for open class monohulls are absolutely straightforward. They must have a maximum hull length of either 60 feet or 50 feet. They must be monohulls (i.e., no concavities in the underbody). They should exhibit a minimum righting arm of 0.4 meters at 90°, and a 20° maximum change in heel angle when all moveable ballast is transferred from one side to the other. Other than a two-meter limit on the extension of spinnaker poles beyond the bow, the rig size is essentially unrestricted. Likewise, there are no limits on draft, beam, or minimum freeboard. The minimum righting arm is required, but there is currently no limit on the minimum heel anglewhen the boat’s righting tendency shifts to a capsizing tendency. In the current crop of super-wide, low-slung designs, the limit of positive stability can be as low as 110°.

Because a wide, scow-like hull offers much greater form stability than a narrow one of similar displacement, it takes considerably more water ballast or lateral keel offset to heel the wide boat to the allowable limit of 10° a side. In effect, the wide boat receives double value from its exceptional beam: both the extra sail-carrying power created by its inherently greater form stability and the extra sail-carrying power produced by additional moveable ballast. In practice, a narrow boat is also burdened more by the added displacement of water ballast because it lacks the abundant reserve buoyancy of a wider hull.

But voyaging sailors should bear in mind that beam in itself is definitely not a speed-enhancing featurejust the opposite. More beam increases resistance in all conditionsdramatically so in head seas. Designers and handicappers have understood this since the early days of yacht racing. Designers have come up with a variety of features, such the notorious hull bumps of the IOR era, to make boats appear wider (i.e., slower) than they actually were.

Limiting the heel change induced by shifting ballast to 10° per side is a rule aimed to ensure that a yacht can recover if caught with ballast to leeward after an accidental gybe or major wind shift. For the most part, the 10° limit has proven to be a sensible guideline, but some competitors have reportedly found ways to stretch the limit while still measuring in. Some boats, particularly those with canting keels, also have aft water ballast tanks on the centerline that are filled to hold down the stern for heavy-weather running. By loading stores far aft and filling aft tanks, the lateral stability of the boat can be jacked up to artificially high levels at measurement time, much as IOR boats used to be trimmed down at the bow to obtain a more favorable rating.

Wave-induced capsizes

The breaking-wave capsize phenomenon came under intense scrutiny following the ’79 Fastnet Race, during which at least 18 boats were rolled 360° one or more times and five remained inverted for periods of up to five minutes. These “type II knockdowns,” together with a variety of other serious mishaps that altogether cost 15 lives, prompted an exhaustive capsize study conducted by a joint task force from the United States Yacht Racing Union and the Society of Naval Architects and Marine Engineers.

Their conclusions, published in 1985, can be summarized as follows:

· A big boat is less likely to be capsized by wave action than a small one, largely due to its much higher “roll moment of inertia.”

· Boats with intact masts are much less likely to be flipped over.

· Wide boats are at greater risk of capsize because the “downhill” hull margin tends to dig in as the boat is flung sideways by the breaking wave.

·Boats with low limits of positive stability (120° or less) are much more prone to capsize and to remain inverted after capsize.

· By active sailing or deploying drogues or sea anchors to avoid lying beam-on to breaking seas, the risk of capsize can be greatly reduced.

The five-year study also developed two methods for determining susceptibility to wave-induced capsizes. One is a fairly demanding calculation of “capsize length”a figure that attempts to quantify whether a given yacht is either more or less at risk than a conservative, moderately proportioned keelboat of comparable size. Some of the input data are hard to come by, but a contemporary open class 60 would probably have a “capsize length” of about 30 feetconsidered the lower limit for offshore work.

The second is a somewhat simplistic “capsize screening formula” based solely on displacement and overall beam. This easy-to-apply formula is often used to determine eligibility for offshore races and to help gauge whether a particular boat is appropriate for ocean passage-making. The equation is: maximum beam (feet) ÷ cube root of (weight in pounds ÷ 64). Screening values greater than 2.0 are considered dangerous territory.

On this basis, a open class 60 displacing 20,000 pounds with a maximum beam of 19 feet has a screening value of 2.8 and is considered at serious risk of wave-induced capsize. To lower the screening value to the 2.0 threshold value, either maximum beam would have to be reduced to 13 feet, seven inches or displacement boosted to almost 55,000 poundsa whopping 275% increase! For sake of comparison, a Melges 24 sports boathardly an ideal choice for the Southern Oceanhas a capsize screening value of 2.7.

Needless to say, the French designers who lead the charge in open class design, as well as the owners/sailors of the state-of-the-art boats, feel these formulae are unrealistic and far too conservative. Given the political interests involved, it’s very unlikely that new rules for upcoming global races will either change maximum beam restrictions or force substantial displacement increases. The international committee studying the open class safety problem is dominated by around-the-world veterans: Sir Robin Knox-Johnston, Phillipe Jeantot, Mark Schrader, Nandor Fa, and Jean Van den Heede. No yacht designers are on the committee, but most members have an interest in existing race boats or are otherwise involved in the solo racing “industry.” Almost certainly they will strive to find a middle course that doesn’t result in wholesale obsolescence of the existing fleet. Safer race routes? Following the rescue of three Vendee Globe sailors who got into trouble in the Southern Ocean, the Australian government has written to the ISAF suggesting that race organizers should no longer have free rein to sanction routes that send racers into such remote waters.

Of course, terrible weather and remote waters come with the territory in virtually any part of the Southern Ocean. Nevertheless, it might be possible to skirt particularly nasty spots such as the small zone southwest of Australia where three Vendee skippers (as well as Isabelle Autissier in the last BOC) all came to grief. Can racers be kept out of the Southern Ocean entirely? Not likely, given the wildly enthusiastic following for competitions like the recent Vendee and upcoming Whitbread. Preventing sailors from diving so far south on their way around Antarctica would have some safety value in terms of reduced ice hazards.

One straightforward change to current solo race rules that would require (rather than prohibit) propulsion engines definitely makes sense. Tamper-proof electronic monitoring should make it feasible to preclude engine misuse. If her Vendee Globe boat had had auxiliary propulsion, Isabelle Autissier would certainly have stood a much better chance of returning upwind to Gerry Roufs’ last known position. Open class 60s are not designed for windward work, and against a 50- to 60-knot wind Autissier could barely make upwind progress.

Other changes that are likely to receive serious consideration are the inclusion of multihull-style escape hatches in the transom, replaceable transom-hung rudders, and methods for stowing life rafts to ensure they stay aboard and are accessible after a capsize. Realistically, the current focus on making these race boats safer and even more independent seems like the most promising avenue for preventing future problems. It’s also the approach that should yield dividends for 21st century voyaging sailors.

Feedback for voyagers

Judging by the assortment of blue-water yachts found in ports around the world, the great majority of offshore sailors rate seaworthiness and creature comforts well ahead of sheer sailing speed. And considering what speed usually costs, both in dollars and other sacrifices, this is no great surprise. On the other hand, at the leading edge of voyaging yacht development, designers and sailors will continue to pay particularly close attention to open class innovations. And if the so-called “aircraft carriers” can be made reliably self-righting, it should eventually be possible to push up the safe maximum beam limits for voyaging monohulls furtherperhaps to the point that highly efficient rotating rigs will start to make real sense. Greater beam is helpful when it comes to water ballasting, but may lead to problems with pitching and slamming.In part because it’s so hard to appreciably boost the speed of a voyaging monohull without sacrificing self-righting abilities, sea kindliness, etc., an increasing number of open-minded sailors are turning to multihulls. Certainly, once a sailor is willing to consider a sailboat that will definitely not right itself in all circumstances, the combination of superior speed and shoal draft becomes an enticing one. Multihulls have accounted for about 15% of all new sailboats larger than 30 feet sold in the U.S. during the past three years. And in the context of safety, it’s worth noting that multihulls are inherently resistant to wave-induced capsize, thanks to relatively high roll moments of inertia and because they lack deep fins to trip them up if they’re caught sliding sidewise down a breaking wave. A high proportion of offshore multihull sailors deploy drogues and/or sea anchorsreportedly with excellent success.

The fact that sailing a Vendee or Around-Alone race is statistically safer than climbing Mount Everest isn’t an excuse for not taking additional steps to limit the hazards involved. Record breaking is a big part of the solo racing game, but it’s unlikely that either a slightly longer around-the-world course or a shift to somewhat heavier, less extreme boats would preclude current marks from being surpassed.

According to three-time winner Christophe Augin, today’s open class 60s can’t be sailed to more than 85% of their potential during the race due to skipper fatigue and risk of breakdown. It’s therefore quite likely that more comfortable, forgiving designs will be able to match the pace of the current generation and, given favorable weather patterns, break records.

Contributing editor Sven Donaldson, a former sailmaker, is a marine technical writer based on the West Coast.

By Ocean Navigator