Indeed, along either U.S. coast, sailors face the same dilemma when it comes to knowing what sails to bring. In San Francisco, where the sea breeze often honks into the high 20s and above, you tend to see sailboats carrying relatively small headsails and reefed mains to match the conditions. But if that sailor heads south to, say, San Diego, where the breeze is typically in the low teens, he or she will be doing a lot of motoring if there isn't a change of canvas on board. Similarly, an East Coast sailor headed south from Boston, where a 140-percent genoa might serve well for most of the summer, will find the boat on its ear when it leaves the Cape Cod Canal and enters Buzzards Bay, where every afternoon a 30-knot blow can be expected to kick up a nasty chop. A large headsail, reefed by more than 20 percent of its sail area, quickly loses the power needed to plow through such sea conditions; a boat now needs to fly a smaller, more efficient jib. And by the time that same cruiser reaches the Chesapeake, the call will be for a large, lightweight sail for the notoriously light conditions often found there.