Darby’s Universal Joint

Darby’s universal joint was a key improvement to the sailboard and remains a distinguishing feature on windsurfing boards today.

Generally, a universal joint is a fastener that allows two parts to flex with respect to each other, but not rotate. Darby’s universal joint could swivel as well, allowing the sailor to drop the sail in the water if necessary, to steer by tipping the sail, and even to spin the mast and sail around.

Darby experimented with different ways to attach the sail to the board. He tried metal and rubber joints, but they weren’t flexible enough. The mast would turn, but it would also pop a hole through the sail. “It’s dangerous if you’re in the middle of the ocean, alone, and the sail doesn’t work.”

Darby solved his problem using an 18-inch length of nylon rope and some household hardware. The rope is both tough and flexible. “It’s elastic, like a large, strong rubberband. It bends and stretches. It can handle a 300-pound pull and has a tensile strength of 1,000 pounds. And it lasts a long time.”

Some modern windsurfers still use the nylon-rope universal joint, but most use better materials--like urethane--that have eliminated the safety problems that Darby discovered in his early trials. But Darby’s still a believer in his nylon rope. “[The new joints don’t] hold up as long as nylon--only a few years.”

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