Examples from the Web for centerboard
French Pete put his head up on the other side of the centerboard, his eyes heavy with sleep, and made them welcome.The Cruise of the Dazzler|Jack London
When he looked again there was but one, a figure sprawled along the keel, clinging to the centerboard.Cap'n Eri|Joseph Crosby Lincoln
The middle one of these three planks was omitted at the centerboard case to form a slot.The Migrations of an American Boat Type|Howard I. Chapelle
You were right in insisting on shallow draught and a centerboard.
The Rowan, drawing little water when her centerboard was up, would shortly be afloat.