The telltales on both sides of the sail must be visible to correct sail trim. Normally, the red and green tapes can be seen through the sails with light behind them, but many sailmakers sew-in a see-through window to make sure.
Boating presents too many variable and unpredictable situations for mathematical analysis. It’s an art. As such, it draws on all your senses. You must see, hear, feel, smell, and perhaps even taste the inputs around you and your boat. You must open yourself to every clue available to every sense. You process them in a kinetic, focused response to moment-by-moment conditions.
Telltales can be the bits of yarn, ribbon, or tape fixed to a sail to serve as visual reporters of the sail’s performance—how efficiently it’s using the wind. Here, we’ll take the definition of “telltale” a step farther, to include some of the less-mechanical ways good skippers shape their performance. You may have learned theory, but until you “listen loud” to the clues all around you and your boat, the whole experience of becoming part of your boat and the wind and the water will be abstract. This is seat-of-the-pants business.
