13.1 Overview 13 Trim Tabs
13.1.1
Trim tab principles of operation Trim tabs are plates, installed in pairs, used to control the pitch and roll of a boat by directing water as it flows past the transom. They work by harnessing the hydrodynamic forces exerted by moving water, so the boat must be in motion for the tabs to have an effect.
WITH TRIM TABS IN USE
WITHOUT TRIM TABS
Figure 14-1.
Trim tab safe operation • The trim tab actuators are powerful mechanical devices that can cause injury. Ensure no one is at risk of being injured before operating a tab when swimmers are in the water, or when operating the tabs on a trailer with people or children around. • Only use the trim tab system as intended. • Do not use tabs as a boarding step. • When lifting the boat, do not place the lifting straps or forks on the tabs or actuators. • Do not push or pull on the tabs or actuators when putting the boat on or off a trailer. • Do not tie off or secure anything to the actuators. • See a marine technician for repairs if the trim tabs, actuators, or controller are modified, damaged or not working correctly. • The controller and actuators are not user serviceable; do not attempt to disassemble. • The trim tab system is not a toy. Do not allow children to operate the system. When a tab is lowered, the directed water flow will exert an upward force at the stern of the boat. If both tabs are lowered at the same time the upward force at the stern will force the bow down (pitch control). If only one tab is lowered it will force the bow down on the opposite side, causing the boat to roll (roll control). The combination of pitch and roll is the boat’s attitude. By adjusting the boat’s attitude, the boat operator can get on plane faster, stay on plane at lower speeds, increase top speed, correct a small list, improve ride quality and visibility, reduce porpoising, and improve fuel economy. WARNING! Exercise sound judgment when using trim tabs in challenging sea conditions. In some cases the safest action is to run with tabs fully retracted.
13.1.2
13-1
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