The exhaust exits at the bottom of the vertical fin. The tower is crowned with a 10-storey vertical fin. They have large wingspans, a very large cargo hold, and a very tall vertical fin. Preliminary design studies had employed twin vertical fin/rudders. There are no moveable horizontal tail surfaces, only the vertical fin with rudder. Each wing had a large aileron and the vertical fin carried a large rudder. It has been used for the vertical fin on seaplane hulls and floats. The aircraft has a T-tail, with both the vertical fin and the horizontal surfaces swept. The Merlin's fuselage and vertical fin represented Swearingen's contribution to the overall design. The Ababil has a cylindrical fuselage, a sweptback vertical fin, and a pusher engine. There is a flap-like, vertical fin surrounding the pointed tail. The vertical fin was mainly royal blue, with five white stars prominently displayed. The larger vertical fin was supplemented by a ventral fin for high-speed stability. The tailplane set halfway up the vertical fin (with cutouts to allow rudder movement). A tailless type may still have a conventional vertical fin (vertical stabilizer) and rudder.