Wing Sail Foil Testing - Trim Tab Size and Control Authority

One objective of testing was to clarify the relationship between trim-tab size and control authority. This was investigated by splitting the trim tab into two equal halves and comparing the aerodynamic response when operating one half versus both halves together.

Test foil with split trim tab allowing testing of a full size and half size trim tab

As expected, the relationship between trim-tab area and effectiveness proved to be approximately linear. Tests conducted with the wing pivot at 18% chord showed that halving the trim-tab area produced roughly half the change in angle of attack. The results confirm that, within this range of operation, trim-tab authority scales proportionally with its surface area.