Hysucat

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[edit] HYdrofoil SUpported CATamaran

Abbreviation and registered trademark for a foil-assisted multihulled vessel, coined by the concept's inventor, South African naval architect Professor Karl-Günter Hoppe, Unistel Technologies and Stellenbosch University. See also Hysuwac[1] [2]

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[3] In a hysucat, a hydrodynamic lifting foil, or wing is added to conventional catamaran hulls. When the vessel moves through the water, the foil lifts a percentage of the vessel's weight, causing both demi-hulls to rise out of the water, reducing wetted area and related hydrodynamic drag. Prof. Hoppe's concept and patents involve a gently swept, chevron shaped wing of thin cross section. In a typical application, the main wing is located slightly ahead of the fore-and-aft midpoint of the vessel, runnng laterally between demi-hulls. This foil attaches to each demi-hull at or near its lowest point in the water. Pitch stability is maintained by twin horizontal fins, bolted abaft to the inboard sides of each demi-hull. On smaller vessels, these fins may be set permanently or on larger vessels they may be adjusted via hydraulic actuators to achieve the best hull pitch angle while cruising.

Catamaran hulls have long been recognized by the sailing community, and are now gaining status as powered vessels because of their lower drag and superior seakeeping, when compared to similar monohull vessels. In an era of rising petroleum fuel prices, naval architects and boatbuilders are increasingly turning to multi-hull technology.

Extra mass for stability is a normal requirement in hull design, but the natural stability of two hulls obviates the need for this extra mass. Breakthroughs in multihull design such as Swath, (Small Waterplane)catamarans and wavepiercing hulls reduce the hull size at the critical, drag-producing waterline, leading to 40-knot car ferries and even faster military craft that are able to operate at high speed across even rough ocean passages. Narrow, thin demi-hulls artificially create higher length-to-width ratios that reduce drag at slower, displacement speeds.

Since catamaran forms offer the option of reducing engine power while maintaining the speed of a monohull, or keeping the same sized engines and traveling faster, commercial customers and pleasure boaters are showing increased interest in catamarans.

Seeing the potential, in the 1970s Dr. Hoppe concluded that catamarans were a logical hydrofoil application because no underwater struts or structures would be required. Shallow water would not pose a problem because hysucat foils do not increase a vessel's draft. Because hydrofoil assisted catamarans never completely leave the water, their demi-hulls continue to provide stability without the need to hand "fly" the vessel or rely on complex computer pitch and roll controls.

Properly designed, a hydrofoil assisted vessel should achieve much higher speeds, without any increase in power or fuel consumption. By raising a vessel nearly out of the water and supporting most of its weight on foils, hulls are less exposed to damaging wave impacts and the unpleasant motion they create. Hydrofoils operate below the surface of a wave, slicing into, instead of riding on top of a wave.

Hoppe's tank tests and prototypes validated his theories and produced impressive data. The best results were obtained above 30 knots, where hysucat foils typically lift 60 to 80% of a vessel's weight. Findings predict that a foil-assisted catamaran would:

- Travel up to 40% using a vessel's existing engines - use as much as 30% at a given speed - Produce fewer emissions at a given speed or over a given route - Have about a 30% greater range - Experience less unpleasant pitch and roll motion. - Display superior seakeeping in rough conditions - Produce a smaller, less hazardous wake

Today, hysucat technology is being used on small boats, primarily RIB, (Rigid Inflatable Boats)and larger yachts and commercial boats. Sizes range from 5 to 36 meters.

Dubai pleasure boat builder Gulf Craft was able to increase the speed of its 12 meter pleasure craft from 23 knots to 32 knots, by installing hysucat foils. A 6.5 meter RIB boat reaches 50 knots in open ocean water, on two 50 HP. outboard motors, while a conventional monohull boat of that size and power would need protected waters to reach a likely top speed of only 25 knots.