Directional stability
The Hurley 22’s rudder skeg helped directional control when travelling fast but made her less agile than the Alacrity in low-speed manoeuvres, when it resisted sideways motion and ‘handbrake turns’ were no longer an option. She was also untrustworthy when running in big waves with a fading wind, a trait that a ects many yachts and demands careful concentration when a steep swell is rolling up astern. As a wave passes, the water undergoes a circular motion: up, forward, down, back and repeat (see diagram top right). At the crest the movement is a forward surge and reduces the in uence of the rudder (diagram below). For instance, on a steep wave with a period of ve seconds and a height of three metres the forward surge at the crest is at approximately four knots. If the boat is running at a gentle five knots, then as a crest comes up astern the ow over the rudder is suddenly reduced from ve knots to one knot and the helmsman will struggle to maintain control – a common cause of broaching. The Hurley 22 may have been particularly susceptible because the rudder was set well forward and had a short lever arm in relation to the keels.
I once sailed with a companion who had seen a preliminary version of the design in which the rudder was hung in the conventional fashion, on the trailing edge of a single keel. In the diagram on page 89 the hatched line shows the original keel pro le for the n-keeled Hurley 22 with the skeg-mounted rudder very close to that keel, so perhaps there was just a quick adjustment on the drawing board. Several yachts from that period (eg Roundabout & Clarionet) had skeg-hung rudders close to their keels and were notorious for broaching. I reckon the Hurley 22 would have been even better with a transom-hung rudder.