Clapp gave his time as well as his money to causes that he deemed worthy, chief among them the Boy Scouts of America. The Boy Scouts had played an important role in his life from age 12, when he joined Troop 5 at Polytechnic Elementary School in Pasadena. As a young man, he served as scoutmaster of Troop 37 in Tacoma. He later held several administrative positions at the state and regional level. In 1971, Clapp was elected national president of the Boy Scouts. He estimated that he flew almost a quarter of a million miles during his year as president.