It does not matter as much with what hemisphere you are in as it does the position of the earth in relation to the sun. There is a very complicated formula to figure this out. It changes almost every season from straight, to right, to left helicle. Actually an archer that works for NASA came up with the formula a few years ago. This is something pretty knew and is still being tested. Maybe someone here can post it. And yes, people on the southern hemisphere do the opposite as the north so when archers from countries as australia come to europe or the US, they have to re-fletch thier arrows. The point is that the earth will have your arrow turning one way and your helicle can be turning the other way causinbg poor flight. It is ideal to have both going in the same direction.