Actually, grooves in wooden shafts were supposedly quite common in American Indian arrows. REad Jim Hamm's books on indian bows and arrows. He said it helps keep them straight. I've tried it on a couple and had mixed results. However, this is mainly relating to shoot arrows not split wood/doweled shafts like cedars. My problem was I could seldom get a shoot arrow straight enough to tell if the grooves helped keep it that way. If I recall correctly, I think there was something about reducing stress and increasing surface area that were supposed to help. Maybe one of the primitive archery types will chime in who has more expereince than I do....