Harry C is right on. a 60 degree bank, level turn produces a loading of 2 g's whether it is done in a J3 or the Concorde. However how many G's can be pulled is a more complex problem. Full size aircraft use what is called a VN diagram. Without having one of these tho, we're looking at basically how much lift the wing can develope and how much authority the tail has to move the angle of attack to it's angle for maximum lift. even tho there may not be enough power to ofset the high induced drag at high angles of attack inertia alone would allow a momentary peak in g loading. The best way to find this out would be to put a recording G meter on your plane and then go wring it out.