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Sunday, November 19, 2017

Designing A Record Breaker

August 2, 1999

Incat Australia Pty. Ltd. is widely regarded as a premier builder of high-speed ferries, and that reputation was enhanced with the production of three wave-piercer catamarans, which hold the distinction of being the fastest ships ever to cross the Atlantic. The two latest, the Catalonia and the Cat-link V are from Incat's line of 299 ft. (91 m) wave-piercer class of fast-ferry vessels. They made their individual record-breaking journeys across the Atlantic within weeks of each other, at the average speeds of 39 knots and 41 knots, respectively. The wave-piercer fast-ferry vessels have been launched from Incat docks in Hobart, Tasmania, Australia, since September 1997. The high-tech ferry evolved from the successful computer-aided-design (CAD) development of a series of car ferries including 243, 256, 266 and 282 ft. (74, 78, 81, and 86 m) vessel ranges. An efficient assembly line, and a reputation for speed and great safety, has given Incat a sizable piece of the world's ferry market - almost 40 percent of the world's high-speed car ferries have been built by Incat over the last eight years. A Deal With The Devil (Cat) TT-Line introduced the 299 ft. (91m) wave-piercing class of ferry catamarans by initiating a four-month charter of the Devil Cat across Australia's Bass Strait, between George Town, Tasmania and Port Melbourne, Victoria. This route is 227 nm, the longest non-stop open-sea fast ferry route in the world. Devil Cat crossed the route regularly in less than six hours. The 315 ft. (96 m) class ships carry 900 passengers and crew, as well as up to 240 cars. In April, the Devil Cat sailed to Canada to operate 14 hours a day during summers between Bar Harbor, Maine and Yarmouth, Nova Scotia, and its name has been changed to "The Cat." It has been very successful on its new route. TT-Line secured a larger 315 ft. (96-m) wave-piercer in its place to run the Bass Strait route in the 1998-1999 season. Design Evolution With CADKEY The wave-piercing Incat catamaran design was first developed in the early 1980s, and has undergone 15 years of refinement. Each of the slender, twin hulls is divided into eight watertight compartments, and the shape allows the hulls to pierce the waves rather than ride over them, giving the vessel exceptional rough sea performance. The hulls are typically 10 percent immersed at the bow, with 10 percent reserve buoyancy. The remaining 80 percent reserve buoyancy is held in the forward central hull, located above the loaded water line. These ratios maintain the vessels' stability all types of weather conditions and sea angles. The hull form for the 299 ft. (91-m) ferries is a full redesign of the Incat catamaran design in CADKEY mechanical CAD software (Baystate Technologies, Inc., Marlborough, Mass.) "CADKEY is used here alongside AutoSHIP and MaxSurf by the naval architects to develop the hull shape," said Lee Hedd, Incat Naval Architect and CAD Administrator. "This combination enables the designers to use the specialized buoyancy distributions and weight balance control of the traditional hull-design packages, and through FastSURF, bring that shape into CADKEY for detailed comparisons and design checks. The simplicity and flexibility of 3D modeling in CADKEY makes designing the required Incat hull shape much easier." The 91-m class of ships had interesting and challenging design parameters that required generous use of the software's 3-D modeling features. Four massive water jets speed the ferry along the waves - each one pumping 19.8 tons of water per second. To meet with new regulations requiring the bridge to have a 360-degree view, the full-width wheelhouse has been moved forward from the smaller-class ferry designs. The wheelhouse is fitted with central and wing control positions for docking facilitation. Passenger comfort is, naturally, paramount to a vessel of this nature's success, and according to the builders, these ships are built for speed and comfort. According to Hedd, "The anti-vibration mounts are placed on the 3-D superstructure model and checked for required clearances and tolerances before the final installation details were decided." Incat then enhanced the "total passenger experience" by including two sheltered sundeck areas behind the wheelhouse. These offer an expansive view of the horizon and a good look inside the wheelhouse. The interior design of the 91-meter ships is provided by Incat's In-house Design Group (IDG), and their mandate is to maximize onboard revenue potential while still retaining the unique style and comfort for passengers, keeping in mind that the ships will be used on long open-seas routes. Seating for the 877 paying passengers is accommodated with aircraft-style seats. The upper passenger level has a bar with banquet style chairs. "We even used CADKEY to arrange and detail the interior of the passenger cabin. The IDG can quickly provide and modify layout proposals for customers, including 3-D conceptual models, and then once the interior layout is finalized, IDG provides all of the required 2-D construction drawings for the interior. The very plans that the customer agrees on become the plans used to build the vessel. The ability to use one CAD package for all of this has proven to be very cost-effective," Hedd said.
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