When the wind’s so light your pipe smoke goes straight up (or it used to, before having fun was banned), any decent boat with a clean bottom will still sail. She won’t go anywhere, however, if her sails are flat. So ease those halyards and outhauls, give the close-hauled sheets six inches of slack, back off the kicker and don’t try to point too high. Oh yes, and sit anyone spare to leeward to induce an angle of heel. That way the sails will drop into shape and what breeze there is won’t squander its energy trying to blow the sails right way out!