The pilot told investigators that after takeoff he experienced a primary trim failure but continued to his destination airport using secondary trim. During final approach in clear daylight conditions, the pilot reported difficulty locating traffic and noticed his airspeed was too high to lower the landing gear. After spotting the preceding aircraft on short final, he “continued working the trim” using toggle switches on the center pedestal. He told investigators that during the landing flare he heard “an unusual noise like something scraping.” He then performed a go-around and discovered that he had not extended the landing gear. He lowered the gear and landed without incident. The turboprop twin suffered substantial damage to its fuselage.