In normal sailing conditions, in order to set the wing sail more efficiently, both flaps can be independently adjusted to match the different wind speeds occurring at different heights above the water’s surface.
As Hubbard notes, “The wing sail has superior performance in mid-range conditions, but the real challenge is to make sure that the rig is safe in all conditions, and can also perform well in light-air conditions.”
The AUSV relies on two safety systems to keep the platform stable, an Internal Navigation System (similar to those used on airplanes), which measures pitch, roll, and yaw, and a series of load cells. When the computer recognizes that the craft is overburdened, the computer trims the wingsail to spill air and reduce the load. The load cells, the nav software, the computer(s), and the foils work together to avoid capsizing at all costs.
According to Harbor Wing Technologies, the hard sail is 50 percent more powerful than a conventional sail, can sail closehauled, and tack through 50 degrees, but has trouble sailing dead downwind. Interestingly, the wing sail itself always tacks through the wind, even if the vessel beneath it is gybing.
Harbor Wing Technologies has built a half-scale 30-foot version of the AUSV (it does not use hydrofoils), which has passed sea trials, including an exercise off Hawaii where the AUSV sailed through a complex set of waypoints, yielding a cross-track error of less than 16 feet. Harbor Wing Technologies plans to build a full-scale 50-foot hydrofoil vessel within the next year. Thus far, military and scientific organizations such as NOAA have shown the most interest in the craft, but Harbor Wing Technologies hopes the technology will also be used in certain passenger ferries, by sailors who no longer want to fuss over sail trim, or by power boaters who are feeling the pinch at the pump.
For more information, check out www.harborwingtech.com