State of the Art
At some point every skipper dreams of making a long offshore passage—maybe across an ocean, to paradisiacal tropical islands, or to the Arctic. But when dreams close in on reality, mundane issues creep in: What's the most seaworthy hull? What if the engine breaks down? Will I get seasick? Enough, already: Worrying too much will drive you right into the arms of the nearest golf pro.
Thanks to evolutions in design and engineering, long-range cruising powerboats—passagemakers—are more reliable, more efficient, and more comfortable at sea than boats of even a few decades ago. Stability and engine failure, the two biggest concerns of cruisers, have been dealt with in innovative and sometimes surprising ways. But don't take my word for it: I asked six experts for their thoughts on the state of the passagemaking art.
Lou Codega is a Webb Institute- and MIT-trained naval architect whose designs turn heads everywhere. He relies on form stability to keep his shallow-draft, roomy Great Harbour 37 and 47 cruisers (built by Mirage Manufacturing) on an even keel. The highest maintenance items on any ship are the roll fins, explains Codega, who's done design work for both the U.S. Navy and Coast Guard. Paravanes, which are similar to giant steel fishing lures that stabilize a vessel underway, may be great in the perfect storm, but they're hard to deal with; fin stabilizers are expensive, complex, and vulnerable to damage. "The best solution is to build stability into the hull," he says. He combines a wide beam, hard chines, and a low center of gravity to create a stiff hull whose natural roll period is short. Serious rolling results when the natural roll period of the boat matches that of the waves it's moving through—hull and waves work in harmony, and the resultant roll is much greater than the size of the one the waves alone would produce. With the Great Harbour design, that happens with small, harmless waves, not big, nasty ones. When the waves increase in size, the hull "platforms" the surface and, rather than rolling, moves relative to the angle of the wave face. "This isn't rocket science," Codega says. "It's analogous to stiff springs on a car versus a sloppy suspension."
Naval architect Patrick Bray doesn't like paravanes, either: "As anyone who has used paravanes will tell you, sooner or later they come out of the water and straight at you." Bray, whose designs run the gamut from dinghies to megayachts, expedition yachts, and commercial vessels, relies on stabilizers, but with a difference: Rather than active fins alone, which are susceptible to damage, he often puts a fixed fin ahead of the movable one. The arrangement is like a skeg and rudder, with the fixed portion providing both a stabilizing effect and protection for the movable fin. For clients who want the ultimate in simplicity, he designs all-fixed-fin stabilizers, "like bilge keels on a sailboat," that can be modified to add a movable fin later on.
Bray's latest designs incorporate bulbous bows, too. A bulb creates its own bow wave, slightly ahead of the bow wave created by the hull. The two waves intersect, reducing each other's height and overall resistance. Bray says bulbous bows reduce fuel consumption by a minimum of ten percent while reducing pitching up to 50 percent, letting you run faster at the same comfort level. A bulb also pulls the bow down, he adds, making the boat run more level, and provides an excellent collision bulkhead. Bray has used bulbs on hulls as small as 40 feet.
But not everyone agrees on the value of bulbous bows, especially in smaller craft. Larry Polster, vice-president and part owner of Kadey-Krogen Yachts, says that despite tank-test results, bulbous bows don't work on hulls less than 60 feet. The tests show ten- or 15-percent performance improvements, but the test simulates calm seas. That doesn't translate to the real world, he says; in fact, the bulbs tend to increase pitching, especially in a head sea. Jeff Leishman, chief designer and co-owner of Pacific Asian Enterprises, offers bulbous bows on 62-foot-plus Nordhavns but thinks they "are more trendy than anything. The bulb comes out of the water a lot. But they reduce resistance under some conditions."
Both Polster and Leishman are moving toward another new trend in passagemakers, one that Bray and Codega are already embracing: twin engines. Kadey-Krogen's 58 is standard with twins, while a single is optional; Nordhavns from 55 feet up can be ordered with twins, although Leishman thinks single-screw with dry exhaust is still the way to go at that size. Codega's 37 and 47 Great Harbours are twin-diesel only, and many of Bray's designs are twin screw. Why? With a single-screw vessel, greater horsepower means a bigger prop, which means added draft and restrictions on gunkholing, cruising the Bahamas, and even heading south on the Intracoastal Waterway, which gets shallower every year. If caught near-shore in bad weather, smart skippers look for a place to hide—a shallow draft makes more storm holes accessible. Structural skegs ahead of each prop provide protection against damage.
This article originally appeared in the July 2007 issue of Power & Motoryacht magazine.