It is essential for proper, safe, and above all, comfortable navigation. Often on small boats it is enough to shift weights to get the boat in the right position, but for larger boats it is not so simple. The main element influencing the longitudinal tilt of a hull is the center of gravity, or geometric center of mass balance. At this “ideal point” the overall displacement is added up; the transverse balance (tilt to starboard or port) and the righting ability of a hull also depends on this position. In fact, if the center of gravity is not on axis with the keel, the boat will lean to one side, and if it is too high, transverse stability will be reduced (see the typology of fishermen with fly and tuna towers). How then to “shift” the center of gravity without moving the weights on board? With the help of flaps or trim variators.
Flaps down
The proper use of flaps provides many benefits starting with the pleasure of sailing. Consumption is optimized and unnecessary stress on the boat is avoided.
Flaps up
If the hull is overloaded and flaps are not used, unpleasantness can arise. Moreover, in rough sea conditions, improper trim can also be dangerous.
Too high
In some flap installations it is possible to create a downforce effect that tends to crush the stern. Be careful not to overdo it; this solution should be used only when actually needed.
Bass
Keeping the ailerons tilted downward causes the bow to heave. Under normal conditions this trim unnecessarily burdens the structure, increasing fuel consumption and decreasing speed.
Reset
If the boat is well balanced, the use of flaps is not essential. If possible, it is better to act first on the distribution of weights on board than to insist on the use of ailerons.
With little angle
By lowering the flaps slightly at medium speeds, you can keep the hull in perfect glide, and by “playing” with the throttle, you can reduce the rpm to optimize fuel economy.
Full-low flaps
Use only in extreme conditions and never at high speeds, especially on fast boats. Remember to retract them completely when mooring: algae and dog teeth seriously damage seals and cylinder stems.
