“Something about reducing drag from turbulence, i don’t understand too well but could do a search”
It has nothing to do with turbulence. And if your first statement was true about long range versus short range, at what distance is the break even point?
“It has nothing to do with turbulence.”
A 3 second internet search proved you wrong.
“Wingtip vortices create turbulence, originating at the leading edge of the wingtip and propagating backwards and inboard. This turbulence ‘delaminates’ the airflow over a small triangular section of the outboard wing, which destroys lift in that area. The fence/winglet drives the area where the vortex forms upward away from the wing surface, since the center of the resulting vortex is now at the tip of the winglet.”
“And if your first statement was true about long range versus short range, at what distance is the break even point?”
Here’s what I found:
“In simple terms, if your average sector length is short (less than one hour) you wont get much the benefit from winglets - unless you need any of the other benefits such as reduced noise or you regularly operate from obstacle limited runways.”
http://www.b737.org.uk/winglets.htm