【The Geometry of GOLF】 10. One-Length system Irons
Bryson DeChambeau uses a one-length system that aligns all irons to the same length, which has many benefits. All DeChambeau irons are 37.5 inches long, have a lie angle of 73 degrees, and have a head weight of 280 grams for a unified balance. If you unify the lie angle, you can unify the swing plane, so you can make the CP shift the same for all irons. Moreover, since it is an upright with a lie angle of 73 degrees, the amount of deviation of the club path due to CP shift when the attack angle is -5 degrees is only about 1.5 degrees, which is about half that of an iron with a lie angle of 60 degrees. Also, with a normal iron set, the length gap of the 4 iron and the wedge are 3 inches (about 7.6 cm), and the lie angle is about 3 degrees different. Then, if the same attack angle is set to -5 degrees, the amount of deviation of the club path will differ by 0.34 degrees between the 4 iron and the wedge. Since 0.34 degrees is equivalent to 0.6%, 150 yards is a deviation of about 1 yard. Whether or not this deviation is a problem depends on the golf level you are aiming for. At the level of aiming to win the PGA tournaments, especially the majors, this gap will not be negligible. Also, when aiming for a pin with draw or fade ball, if the lie angle is the same, the loft change when opening or closing the face will be the same. Moreover, since it is very upright at 73 degrees, the loft change is also small. The loft changes only about half of an iron with a lie angle of 60 degrees. For example, at a lie angle of 60 degrees, a loft is decreased by 1 degree when the face is closed 3 degrees, but at a lie angle of 73 degrees, decrease is about only 0.5 degrees. Then, the error in the carry distance will be reduced. Also, if the length and balance are the same, it will be easier to control the head speed and attack angle. With a normal iron set, the length will be longer with a smaller number of iron, so even if you think you are swinging at the same swing speed, the head speed will be faster. With a one-length iron, head speed control will be simpler and distance control will be easier. In this way, one-length irons have the advantage of being simpler when hitting a straight, draw or fade ball and aiming for a pin. As of 2020, only DeChambeau uses one-length system within PGA tournament players, but more professionals may adopt it in the future.