sentences:  The Rotax engine required a larger planing surface and sufficient induction for its air cooling, so Jacobson developed an entirely new sit-down model to adapt.Jacobson applied for a patent on the sit-down model in February 1968 and received the patent a year later in February 1969.Bombardier entered a licensing agreement with Jacobson for his sit-down personal watercraft patents in order to produce their first model of Sea-Doo, which was produced from 1968 to 1970.