Everyone knows you turn a boat with the rudder. This directs the stern of the boat in one direction and turns the boat by pivoting it around the centerboard or keel. However, steering with the rudder has a couple of limitations: first, you can’t turn if you are not moving very fast because the rudder only works when water is flowing over its surface.
Second, steering with the rudder slows you down. The further you push the tiller to one side, the more the rudder’s surface area will be exposed to the flowing water, and the more the rudder will act as a brake.
Because the rudder has disadvantages, you must use other turning methods if you want to go faster. Here’s where the sail trimmer plays an important role. You may have noticed on a windy day, for example, that the skipper has a hard time bearing off around the windward mark unless he or she dumps the mainsheet. On big boats, the sail trimmers often have more control over the direction of the boat than the helmsperson!
Just like the rudder, your sails can be used to help turn the boat around its underwater pivot point. Sailboards are a great example of how this works. Since boards don’t have rudders, they rely on the position of the sail for turning. When a board sailor wants to bear off, she pushes the whole sail forward over the bow.
This puts more wind pressure forward of the center board, so the bow pivots to leeward. The same principle applies to a sailboat. If you want to turn away from the wind, pull the jib tight and let the main out. .This moves the effective sail area forward, which pushes the bow away from the wind and pivots the boat around the centerboard. If you want to head up toward the wind let the jib out and trim the main in tight. Now the working sail area is behind the centerboard, so the boat will head up.
As a sail trimmer, you should use these techniques any time the boat changes course. It’s very important to ease the main, for example, whenever you are rounding a windward mark, bearing off behind a starboard tacker or trying to keep from rounding up on a reach. Likewise, you should ease the jib a little any time you are luffing into a tack or rounding a eeward mark.
If you consistently use sail trimming chniques to help turn your boat, your gains around the race course will be significant.
Try this: on your next practice day, sail out into open water and remove your rudder. Then practice turning the boat with your sails only. This requires good coordination between the helmsperson on the mainsheet and the forward crew on the jib sheet. If it’s windy, you may need to raise the centerboard a little to move the center of lateral resistance aft and reduce weather helm.