'The DaVinci Curve' - Continuous Line art by Robert Bosch (He refers to this as TSP art: Traveling Salesman Problem. The traveling salesman tries to visit different locations and will try to find a path that requires him to travel the least total distance.)
Adjusting the bottom tension is generally set at the factory and shouldn't need adjustment. The tension on the bobbin case is controlled by a small screw and a curved metal band. Turn the screw that is located next to the thread opening. Remember: Righty, tighty; lefty, loosey!