Complex sentence: Sails are lateen rigged and were traditionally made of pandanus mat sailcloth, though after World War II the islanders switched to canvas, and after 1973 the use of dacron began to increase.
Split into simpler sentences: Sails are lateen rigged and were traditionally made of pandanus mat sailcloth. After World War II sails switched to canvas, and after 1973 the use of dacron began to increase.