Originally Posted by modelerchina
what do winglet/spoiler/fin do for 3D.
those add-ed feature for profile plane will slow the plane for sure, maybe avoid tip stall.
Anyone can logically analyze the purpose to have them in plane, and why it seems only for profiler.
Well that can be a complicated aerodynamic question. Most of the time you find them on indoor planes. The items trailing the ailerons in the pic are basically speed brakes, designed to keep the speed going downhill easier to keep thenspeed constant as going uphill. Alot of times you will see sfg's to help in knifedge flight along with keeping the airflow across the wing in a place to help with flow across the control surfaces. Some planes like the new visionaire has extended leading edges with fences. It keeps the flow across that portion, with more area to help increase stable flight in slow high alpha flight. Just some general thoughts but an engineer could go more indepth. Take a look at some of the threads on indooe competition and you can learn more.
my two cents