Wind vanes refinedOct 24, 2013
Newest developments in wind vane self-steering technology
(page 4 of 4)
Airvane-controlled auxiliary rudder
For over three decades, each self-contained Hydrovane auxiliary rudder unit was built entirely by hand. With a growing customer base, though, John Curry decided to transform the shop in Nottingham, England, into a modern factory and use computerized CNC machines.
Close-up of Sailomat unit shows finely-made parts and a clever mechanism for steering the boat using the wind.
After streamlining production, Curry set his sights on beefing up the Hydrovane’s strength and overall performance. “It is no secret that the average boat size is growing in both length and breadth,” Curry pointed out. “We set out to increase the power and performance of the Hydrovane. The first project was the rudder. The size of the rudder determines the steering power of the equipment. Initially, we thought that would be easy enough, simply make it bigger. Well, we learned there was more to it.”
Besides having to make a new 550-pound rudder mold, he found that as the rudder got larger, the complex hydrodynamics around the rudder surface also changed. “We had to learn more about the balance of the rudder,” Curry explained. “There is an optimal placement for the shaft hole. If it is too far forward, the rudder is hard to turn. Conversely, by progressively moving the hole aft, there is a point when the rudder goes wonky — no longer knows which direction is forward.”
With the aid of an engineering student from the University of Southampton Engineering Department and access to the university’s test tank, Curry’s team finally determined the right rudder balance and moved on to designing a stronger rudder shaft and bearings, along with improvements to the Hydrovane’s internal gearing.
Diminished true wind speeds on ever-faster boats in downwind sailing are placing a new kind of demand on wind vane self-steering systems. Some boats can achieve six knots on a run in less than 10 knots of true wind, leaving only three or four knots of true wind for the airvane. “All self-steering systems have no problems performing in heavy weather,” Curry pointed out. “That is when their source of power (boat speed for servo systems and wind speed for the Hydrovane) is always more than needed.”
Hydrovane’s answer to the need for more downwind steering power is a new extended airvane, now in the final design stage. Hydrovane also offers a new shortened Stubby Vane, equal in power to the regular vane, to accommodate arches for solar panels.
Whatever your cruising plans may be, a wind vane self-steering system should be an integral component of your ship’s rigging. There is a wind vane self-steering product to accommodate every type of deck layout, transom configuration and main steering.
Bill Morris completed a circumnavigation, two-thirds singlehanded, via the Suez and Panama canals aboard his 1966 Cal 30 Saltaire. He is the author of The Windvane Self-Steering Handbook, published by International Marine.