Modern racing Tris are designed to sail with only
the leeward ama in the water, with the main hull
flying clear as much of the time as possible.
( See the BMW A Cup beast)
Thus all three rudders are steerable.
In the tri pictured you can see what look to be
either steering cables or hydraulic lines leading
to the amas. The center rudder also appears
to be retractable.
Islander 30 II 'COOL'