Just as pistons and cylinders play a primary role in a diesel auxiliary, rope and blocks are the guts of every sail-handling system. A few decades ago, Dacron (polyester cordage) ruled the roost. It remains a key player, but stronger, lighter, and less-stretchy options are gaining ground. Racers have embraced Dyneema, Vectran, Torlon, Zylon and a growing list of other odd-sounding esoteric fibers. The old enemy stretch has been tamed, but the big remaining question is whether a running-rigging makeover is worth the expense. It takes a little cost-benefit analysis to answer that question.