A Bennett trim tab in action on an outboard- powered boat. Bennett offers a handful of accessories, including a device that retracts the tabs when the engine is shut down.

Any boat, when you come right down to it, is a collection of compromises—cockpit room vs. cabin room, fishing conveniences vs. cruising comforts, quality vs. cost. Hull design is no exception. An ideal hull shape for planing operation is a poor one for operation at sub-planing speeds and vise versa. A deep-V hull makes for a softer ride in a rough seaway but is more susceptible to heeling than a shallower-V design.

Airplanes have long faced similar problems; their wings have to operate efficiently at low as well as high speeds. The aircraft designer’s solution has been to install moving flaps and slots to effectively change the shape of the wing…