On an aircraft like the ventus there are several sections of control surface
along the T/E of the wing resulting in several 'breaks' in the trailing
edge. My question is - Are the breaks or corners of a deflected control
surface the source of their own little vortices and therefore additional (
very small) drag? I know that the inboard end of flaps is an area that
causes a lot of problems, my ventus has fences fitted there and some people
fit fences to the aileron joints. Just how much drag difference do aileron
fences make given that they increase the wetted area by several square
inches themselves?

Ian