AS the spokes are brought up to tension they will straighten to a degree. The spoke often has a bowing/bend as it leaves the flange, somewhat dependent on the hole in the flange and the thickness of the flange. One trick many builders use is to press on the spoke just beyond the elbow and therefore do some straightening before you begin the tensioning process. Not much is needed to create a spoke that has little bend. You can feel the change as prior to this slight spoke stressing the wheel is fairly stable, the still loose spokes hold the hub in place with the bowing acting as the tension. After the spoke pressuring is done and with no other nipple turning the hub will now flop about to some degree as the spring like nature of the bowing spokes is now gone. Andy.