High-performance sailing

There are also wind-powered vehicles that can travel faster than the wind, such as the rotor-powered Blackbird, which are outside the scope of this article.

[3] Other skiffs that can sail faster than the wind include the 29er, and 49er, both designed by Julian Bethwaite.

[4] In 2013, a new class of catamaran was announced for the America's Cup which can achieve well in excess of double the speed of the wind.

[19] Iceboats on the Hudson River of New York in the second half of the 19th century were as long as 69 feet (21 m) and sailed as fast as 107 miles per hour (172 km/h), a record exceeding any other conveyance in 1885, set by the Icicle.

Runners are made of iron or steel with sharpened edges, which hold onto the ice, preventing slippage sideways from the lateral force of the wind in the sails, as they develop propulsive lift.

Given their low forward resistance, iceboats can typically sail at five to six times the speed of the wind.

The apparent wind measured aboard a craft under power, traveling in calm conditions, VT = 0 knots, would come from directly ahead and at a speed that is the same as the boat speed over the bottom (VA = VB + 0 = VB).

[26] When drag angle of the hull is negligible, the formulas for calculating VA and β (the apparent wind angle) are:[27] A sail generates lift with a forward propulsive component and a sideways component, based on an optimum angle of attack that is constrained by the apparent wind, VA, being forward of and approximately aligned with the sail.

[28][29] Garrett introduces the beta theorem (or course theorem) as a way to understand how apparent wind angle results from the interplay between the driving force from the wind and the resisting force from the water (or hard surface), the result of the net effect of two counteracting foils, the sail in the air and the keel in the water.

Efforts to overcome this limit is evident in the streamlined hulls of high-performance iceboats and the improvements in drag reduction on planing dinghies.

[3] The points of sail at which high-performance sailing craft can achieve highest speeds and achieve the best speed made good[31] over a course span between a beam reach (90° to the true wind) and a broad reach (about 135° away from the true wind).

[3] Bethwaite explains that high-speed sailing demands independent action of both the tiller and the mainsheet, whereby the person at the helm avoids responding to gusts and, instead, eased the mainsheet as needed, thus increasing the boat's velocity made good over the previous technique of pointing the craft more into the wind.

This has the doubly beneficial effect of relieving the heeling force of the gust and allowing the craft to sail yet faster off the wind.

18ft Skiff in Kiel Harbor
Oracle sailing hydrofoil catamaran with wingsail in the 2013 America's Cup
Apparent wind, V A , on an iceboat: As the iceboat sails further from the wind, the apparent wind increases slightly and the boat speed is highest on the broad reach (C). Because of a small β , the sail is sheeted in for all three points of sail.
β is the apparent wind angle from course over the water. [ 26 ]
Total drag angle ( β ≈ apparent wind angle) for high-performance sailing craft as a ratio of V B to V T at a course of 135° off the wind, achieved by such craft, as shown. [ 3 ]