ORIGINAL: thailazer
BMatt & Lnewqban..... Good posts! Here's an additional question: My Tiger 2 with fully sym wing flys fast just great with little trim. When I start doing landings (i.e. flying slower) I normally dial in 4 clicks of up trim. Is this because the horizontal stab is less effective at lower air speeds, or simply that I have to increase the angle of attack to fly slower?
Yes, the tail is forcing the wing to adopt a higher AOA, so the coefficient of lift increases for reduced airflow and lift force remains about the same to sustain horizontal flight.
When you dial in 4 clicks of up trim, you are modifying the camber and the AOA of the stab-elevator surface.
By doing that, you are increasing the down lift of the tail, even for the reduced speed.
The down lift pitches the nose of the plane up enough to increase the AOA of the wing as much as the reduced speed demands.
Remember that lift is proportional to AOA and to the square of the air velocity:
http://en.wikipedia.org/wiki/Lift_coefficient