As Pat said, most board bows break from grain run offs. You can increase your odds for success by choosing wider boards, then you can lay your bow out with a lot better grain orientation. Its just about impossible to find a 2" board that doesn't have a lot of run offs. Also always keep the edges smooth and rounded. Boards are a great way to learn, I broke my first seven board bows before I got a shooter, stay with it, the reward of a sweet shooting bow that you made yourself is well worth all the aggravation.