The flaps or trim stabilisers, permit, by modifying the hydraulic flux to the rear of the hull, improvement in the boats behaviour, control and manoeuvrability. By reducing friction whilst augmenting the speed of the boat, you reduce also your fuel consumption.
For the choice of the characteristics of the flaps, you must consider:
-The size of the boat. The larger the boat, the longer the flaps.
-The weight of the boat. The heavier the boat is, the greater the surface of the flaps should be.
-The width of the transom.
-The position of the strakes.
-The type of motorisation (Z-drive, shaft, propeller surface …)
In general, one should choose the greatest width except when the motor or position of the strakes prohibit.The flaps do not require special maintenance (except antifouling). It may require anodes in the case of boats very sensitive to electrolysis (a hole is pre-drilled on the flaps.)