Genoa Car Placement
Your genny sheet pulls both aft, and down on the clew of the genoa. Set the genoa car for best performance tacking into the wind. Pulling aft changes the angle at which the luff of the lower sail meets the wind (angle of attack.) The objective is to keep the lower telltales streaming back with the near or windward telltale dipping 20 to 30 percent of the time with the action of the waves.Pulling down controls the angle of attack toward the top of the sail, keeping it more in line with the bottom. Actually, the wind blows a little faster higher up, so the apparent wind comes more from the beam on high, and you want to ease the downward pull enough to increase the angle of attack to keep the top telltales behaving like the bottom - both streaming, with the windward (closer) telltale dipping 20 to 30 percent of the time. This higher angle of attack toward the top of the sail is called twist.Since we only have one genny sheet, we control the balance of the aft and downward pulls of the sheet by changing the angle the sheet makes at the clew with the genoa car. Moving the car forward increases the downward pull, and decreases twist (do this if the top windward telltale is dipping more than 30 percent of the time while the bottom telltale is just right.) Moving the car back decreases the downward pull and increases twist (do this if the top windward telltale is dipping less than 20 percent of the time while the bottom telltale is just right.)Where to start? Well some sails (like my new Doyle 110, for instance) actually have an arrow pointing at the direction the sheet should take from the clew for a good balance of downward and aft pulls. Without the arrow, I would start with a 45 degree angle of the sheet to the foot of the sail while sailing to windward in lighter winds where I need the full genny. Then I would move it backward or forward until both my lower and upper telltales were flying right. Mark that position, and measure the same position for the other genoa car. Now you have a good set-up for cruising, or to start in a race. You move the cars as conditions vary, tuning the sail to keep the telltales right. Most cruisers will set them and leave them unless there is an obvious problem with the twist of the genny.Finally, you really do need to move the cars forward whenever you reef the genny by rolling the luff onto the roller furler. Our gennies have a second set of telltales to guide this exercise, but you can start with the same angle that works best with the genny all the way out, and then tunning by watching the luff for shaking ("luffing") higher up as the building waves rock the boat.I hope that is clear enough to get you started. There are excellent books of sail trim in the chandlery, and I also have Don's laminated sail trim guides also found there.It's OK to fool around with tuning your rig - it's your boat after all!. It's also OK to get it somewhere near right, and just enjoy the sights and sounds. But I've caught the bug, and will usually stay after the set of my sails until both are pulling as well as I can get them. That is a great part of the joy of the sport for me!DavidLady Lillie