The pilot decided to make a straight-in visual flight rules (VFR) approach to the destination airport after a flight of less than 10 minutes from his point of departure. There was departing traffic at the non-controlled destination airport and the pilot said he became distracted while discussing that traffic with his passenger. The pilot, who said he normally makes sure the gear is down while on downwind, did not use a checklist and failed to lower the gear prior to landing. The subsequent contact with the runway surface resulted in damage to a fuselage bulkhead.