He was born in 1928 and grew up in Wilkes-Barre, Pennsylvania and began building boats when he was 12. His first boat sank, but he fished it out of the Susquehanna River, near his home, and made it into a home for snakes.
Darby and his wife made their home in Saint Johns, Florida, where he died on December 3, 2016 at the age of 88.
Darby first conceived of a hand-operated square sail attached to a catamaran in 1948, when he was 20. In the mid-1960s, Darby conceived the "Darby Sailboard": a hand-held square rigged "kite" sail on a floating platform for recreational use.
Darby had taught himself to sail a 10-foot model on lakes in high wind between 1964 and 1965. He published his design in August 1965 Popular Science magazine, and although it did not show any connection between the rig and the board (i.e., a universal joint; the mast simply rested in a depression on the board) it did refer to a "more complex swivel step for advanced riders not shown." The sail was like a kite and was sailed with one's back to the sail. Popular Science magazine was published in many countries around the world, establishing the Darby sailboard as "prior art" in many legal jurisdictions.
Darby and his wife Naomi organized Darby Industries, Inc. in 1964, with his brother, Kenneth, was also active in the company. However, the sailboard design never gained popularity, and Darby's company ceased operations by the end of the 1960s.