When Alexander Dreyfoos decided to test his next boat he went to one of the world’s windiest, nastiest, most dangerous navigation areas—the North Sea. He took the helm of the unusual-looking vessel he was testing and did something captains rarely do in such rough conditions: he stopped the boat. He then left the helm to check on his wife, who is prone to seasickness. When he found her calmly knitting he knew his search for the perfect vessel was over. Three and a half years later he invited us to see his new yacht, Silver Cloud, on much calmer waters in Palm Beach, Florida.
Story Liz Pasch
Photos Shaw McCutcheon
SILVER CLOUD IS A SWATH YACHT, a design that incorporates two sub-merged submarine-like tubes connected by narrow struts to the yacht structure, which is above the waterline. Until now the design had been used primarily on commercial vessels. The SWATH, or Small Waterplane Area Twin Hulls, has its roots in the late 1800s. When Captain Lundborg, a Swedish retired naval officer, observed whales and other fish swimming below the surface of the water, he noticed how little effort they made to reach their amazing speed and deduced that submerging an object just a few feet underwater greatly diminishes resistance found at the surface. Captain Lundborg applied the principle to the first semi-submerged single-hulled concept, which he patented in 1880.In 1968 a Dutch shipyard launched the first waterplane area twin hull vessel, which eventually led to the current SWATH design used for oil exploration, ferries, military, pilot boats and a 429’ cruise ship built in 1992.
Silver Cloud is German superyacht builder Abeking and Rasmussen’s first SWATH yacht, but Silver Cloud’s owner says being the first to cruise the world onboard a SWATH yacht was far from being his objective when he ordered the vessel. What drove his quest was his wife Renate’s tendency to get seasick, which limited their ability to explore the world’s oceans. “Most of our cruising was on inland waterways, rivers, harbors, and where there is little rough water,” Dreyfoos says. “We would fly to meet the boat and let the captain take the boat across the rough parts. We initially thought that bigger would be better in terms of stability.” The couple moved up in size from a Burger to a Feadship but found their larger monohull still produced excessive motion. At that point Dreyfoos focused his search on finding a design that would truly resist wave motion. “Anytime I saw a new style of boat in a magazine with a different type of technology I looked into it,” says Dreyfoos, who was committed to find a boat that would minimize his wife’s seasick-ness. The MIT and Harvard graduate who holds 10 patents explored options ranging from catamarans, trimarans and jet boats to wave-piercing high speed ferries. He finally heard about the SWATH design and took a year to learn more about the technology.
“This is really a very simple concept,” says Dreyfoos. “If you’re a scuba diver you know that when you’re on the surface it can be rough; you only have to go a couple of feet under the water and you don’t feel what’s happening on the surface. This boat has two submarine hulls that are 11 feet in diameter. They hold the engines, generators, watermakers, compressors, air systems, sewage control and so forth, and are connected by very thin struts to the boats,” he says. Only a minimal area—the struts— is at the waterline, which effectively diminishes the upward forces waves normally exercise. Four stabilizers, two forward and two aft, further increase comfort.
Dreyfoos found that motion reduction while underway is just one of the many advantages to the SWATH design. He is used to flying his own plane to islands he wants to explore, many with limited airfields. “From December to March the wind blows pretty hard so it’s very difficult to fly into those places. People who don’t know better will make the trip once but when they do they say never again because the landing and takeoff is so scary,” he says. The SWATH is an attractive vehicle for island hopping; even at zero speed it is very stable and makes being at anchor comfort-able. It is also quiet. Motors and generators are located in the submarine hulls so mechanical noise is removed from the yacht’s living areas. Access to the subs through a narrow vertical tube is confined but sufficient. Once at the bottom of the tube some four feet under water, the 11-foot diameter of the submarine affords plenty of space for maintenance and repair. Above the water line the yacht’s enormous living spaces boast full windows instead of traditional portholes. Light streams in from all directions. The full-beam salon is twice the width of traditional yachts. Here multiple conversation, dining and entertainment areas comfortably coexist. The area also serves as a gallery for Dreyfoos’ photography. He knows a thing or two about the technology behind the pretty pictures. In1963 he formed Photo Electronics Corporation, a manufacturer of digital color photographic processing equipment that received an Oscar in 1970from the Academy of Motion Picture Arts and Sciences for video color applications developed for the film industry.
Dreyfoos also likes the arrangement for the tender garage, located in the middle of the yacht at the lowest position between the hulls. The garage door swings down from its horizontal position allowing the tenders to be lowered down into the water, about 3.5 feet below. “The beauty of this arrangement between hulls and the garage door actually going into the water is that it provides a protected harbor,” he says. A detachable stairway and platform portside allows loading guests into the tender.
Dreyfoos has yet to find any significant cons with the SWATH design butadmits his shakedown cruise to Florida from Germany by way of Gibraltar, the Canary Islands and the Virgin Islands required both he and the crew to acquire new habits. “The major issue on boats of this type is balancing weight very carefully,” he says. When a gallon of fuel is used, it needs to be replaced with an equivalent amount of water to compensate. The yacht’s two HEM watermakers, which produce 3,600 gallons per day, help achieve this goal. Balancing weight on the transatlantic cruise helped improve the yacht’s performance dramatically and allowed using significantly less fuel than anticipated.
Dreyfoos and his crew will have more opportunities for fine-tuning on the circumnavigation they have planned for the next few years. They hope to spend New Year’s Eve in Sydney but are trying not to structure the trip too much. “I see most things from the point of view of ‘would it make an interesting picture’,” Dreyfoos says. This may be the kind of open minded-ness that allowed him to recognize the potential a commercial boat in the North Sea had to become the ideal yacht on which to travel the world.
SWATH BY THE NUMBERS
All conventional displacement hulls are subject in varying degrees to the upward and downward motion of waves. At the heart of the SWATH design is the observation that waves only exist on the surface of the water and that below the surface the water is calmer. Therefore, waves do not affect a vessel designed with its displacement permanently below the surface. To take advantage of the calmer waters below, builders—Abeking &Rasmussen among them—have developed the unusual-looking SWATH. A&R is the fist shipyard to have built a SWATH yacht. Their design places the vessel’s entire superstructure above the water on top of a platform, which thin struts connect to a pair of submarine torpedo-shaped hulls. The struts are slender to minimize their exposure to waves. The design is similar in some ways to that of a car chassis, with two struts located on each side, a bit like wheels on a car. On the 134’6” Silver Cloud the “torpedoes” are 11’6” (3.50m) in diameter and run about 3’7” (1.1m) below the surface. A 6’10”-air gap between the water surface and the superstructure prevents cresting waves from making contact with the underside of the bridge deck. After extensive testing, A&R engineers determined that the most effective design allocated 80 percent of displacement to the torpedoes (40 percent each) and divided the remaining20 percent of displacement between the four struts. The struts then contribute only in small part to the vessel’s buoyancy; engineers installed ballast tanks inside the underwater torpedo-like hulls to help manage overall weight distribution. Also housed within the torpedoes are the fuel tanks and two 1,100 hp C32 Caterpillar engines, which provide the yacht with a top speed in excess of 14 knots. The vessel has a range of 3,900 nm. Silver Cloud features a Costa propulsion bulb, connected to the vessel’s rudders in the axis of the propeller shaft, to help economize on power and fuel. A&R Engineers calculated that Silver Cloud’s Costa propulsion bulb adds about 0.5 knots to the cruising speed and increases the vessel’s range by about 400 nm. Active fins fitted forward and aft on each hull act a bit as suspension does on a car. Using an advanced electronic control system, the fins help “fine-tune” the vessel’s response to waves. According to A&R, fin stabilizers fitted to conventional ships and yachts are effective in suppressing rolling but do little to prevent pitching, slamming and heaving, which the SWATH does very well. The build contract went as far as specifying the vessel’s maximum acceptable vertical acceleration. During sea trials in a head sea with waves topping 6’, Silver Cloud recorded a vertical acceleration of 0.035g rms and roll angles as low as 1.2 degrees rms (“g” equals the force of gravity and “rms” represents the statistical average.) According to A&R, these numbers are almost never achieved in ships with a hull shorter than 328’. In comparison, the vertical acceleration in cargo ships is limited to a maximum of 0.15 g rms and the NATO naval vessels require a maximum of 0.2g rms. By the time A&R delivered its first seagoing SWATH yacht in 2008, it had already built 10 commercial SWATH ships, including seven patrol vessels. The German shipyard celebrated its100thanniversary in 2007 and has built more than 6,400 vessels since its first, an unnamed 15’ workboat. One of its most recent yachts is an elegant conventional twin-screw yacht that has taken its place this year on the list of the world’s 100 largest yachts.
For more information, visit abeking.com
LOA: 134ft. 5in.
Beam: 48ft. 5in.
Draft: 13ft. 6in.
Construction: grade A steel GL certified ALMg 4.5 Mn/ALMgST0.7
Displacement: 601 tons
Gross tonnage: 926 GT
Engines: 2 x 1,100 hp CAT C32 820 kW
Gearbox: ZF Type 3310
Propellers: 2 x 6 bladed fixed pitch Schaffran
Fuel capacity: 19,300 Gal.
Maximum speed: 14 knots
Cruising speed: 10 knots
Range: 3,500 nm@10 knots
Generators: CAT 2 x 160KW,1x 69 KW
Water capacity: 15,900 Gal.
Stabilizers: 4 x hydro control/MDI
Class: GL 100 A5 motor yacht / MCA LY2
Naval architect: Abeking & Rasmussen
Exterior stylist: Abeking & Rasmussen
Interior design: Kirschstein Designs Ltd /Spectrum designs / Abeking & Rasmussen
Shipyard: Abeking & Rasmussen
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15' Inflatable Rescue boat with 40 hp 4stroke outboard motor.
For further information, contact Michael Rafferty Camper & Nicholsons, 450 Royal Palm Way Palm Beach, FL 33480, Ph: (561)655-2121e-mail: firstname.lastname@example.org