Sherman Poppen, the snowboard inventor who laid the groundwork for a multibillion-dollar industry, has died. He was 89. Poppen died July 31 at his home in Griffin, Georgia. In 1965, while living in Michigan, Poppen was looking for a way to entertain his daughters on a snowy Christmas Day. So he strapped two skis together and held them in place with wooden crossbars. His wife dubbed it a …