A century ago, five- to six-inch paddles were the rule. By the 1960s, 10- to 12-inch “banjo” paddles were most popular, the theory being that wide blades are more efficient in shallow water where you can’t submerge the whole blade. But wide blades are heavy, noisy (they push a vacuum) and awkward. Modern canoeists now prefer 7 1/2-to-nine-inch blades, with eight inches being the standard.