Rudderless Sailing

From the Hunter Magazine 2007 Safety Tuneup [ Hunter http://www.huntermarine.com/ProductNot/ProductNotIndex.html ]

The rudder on a sailboat is extremely vulnerable to damage and is under extreme pressure at all times when being used, including motor sailing. It also is exposed to any hazard that exists in the sea and can be damaged by grounding or receive shock loads by hitting flotsam and debris in the water. Whales and other sea life have been known to destroy rudder blades. It is not uncommon for an anchor line to wrap around the rudder, and for the shock load from wave action to apply enough pressure to overload the rudderstock. There are many ways a rudder can become damaged or inoperable. ... However, the rudder is not the only factor involved in steering a boat, and there are several alternate methods for controlling the trajectory of a vessel in the event of rudder dysfunction. Knowledge of alternate steering methods is an important component of thorough sailing knowledge, and should be part of any beginner’s training. Rudderless sailing is indeed possible; in fact, many junior sailing programs devote a portion of their instruction to sailing the boat without a rudder. This is learned through the study of the boat’s dynamic reaction to sail trim. It is important to understand how a sailboat reacts to sail trim, as this is how you will guide the boat. Not only can learning these skills help you out of a difficult situation, they will advance your knowledge of sail trim and your ability as a sailor.

Imagine a boat resting in the water with no sails rigged. Underwater, the keel or centerboard acts as a fulcrum, called the Center of Lateral Resistance (CLR, indicated by dotted line in illustrations on the top of the next page) somewhere near the center of the boat. If you were to push against the bow from the starboard side, the boat would turn toward the port, rotating on that fulcrum (figure 1). Conversely, if you push on the stern from the starboard side  the boat will turn toward the starboard side (figure 2). These forces can be duplicated using the sails. With only the mainsail rigged, and the wind blowing across the starboard side, the boat will turn toward the starboard side (figure 3). This is because the position of the mainsail is generally aft of the CLR, and the wind causes the mainsail to apply force behind that axis. With only the jib rigged and sheeted in, the same force is applied forward of the axis, and the force of the sail will push the bow away, as if you were pushing the bow with your hand (figure 4).

If both sails are up, sheeting out all the way on one or the other sail can provide the same effect as if the other were the only sail. When the jib is sheeted out, it does not exert any force, so it is as if it were not even there. Similarly, if the jib is sheeted in and the mainsail let loose, the boat will behave as if force were being applied to the bow. Keeping these principles in mind, it becomes evident that changing the trim of the sails can influence the trajectory of the boat. In fact, this should be practiced. Go sailing and lock off the rudder. Try making the boat go in the direction you want by applying the sail trim as we described. If the bow needs to go downwind, trim it in and ease the main. If the bow needs to go upwind, ease the jib and trim in the main. As you become accustomed to how much trim is required (and this will vary from boat to boat), you should be able to steer a course by making minor adjustments once you have the basic trim set up. It will take some practice but it will make you a much better sailor.

To refine this method, we need to understand that a boat is designed so it will slowly head into the wind if the helm is let go (A, fig 5). Accordingly, the mainsail should be eased so that the jib can "blow" the bow back down to compensate. Also, a drag device can be easily improvised to reduce the boat’s tendency to head-up into the wind. For example, a bucket can be tied off the leeward side of the boat, creating a drag (B, fig 5), which reduces the boat’s tendency to turn into the wind. By adjusting the amount of drag (i.e. adding or removing buckets), an optimum combination can be reached. Also, most sailboats when under power will automatically tend either to the port or starboard when the engine is engaged, depending on many different variables from boat to boat. Determine which way the boat turns with just the engine on, and this force can be used to help steer the boat. The idea is to balance all the forces to keep the boat going straight ahead. If you are able to practice and become comfortable with the necessary procedures involved to successfully sail without a rudder, it should greatly boost your confidence in your ability to handle unexpected situations. That is the essence of seamanship.