MOI Part 2--Why Square Drivers?
High MOI is behind the new square, triangle and other unconventional driver shapes and compositions. What will it do for you?As stated in Part 1, MOI is the point (or moment) at which an object resists rotation, so changing the mass around this point changes the MOI. The composite drivers such as the FT3, Cobra Comp and Cleveland Comp were all examples of using different materials, e.g., carbon instead of titanium, to shift weight away from the center of gravity and increase the MOI. (The forerunner of this trend was the Yonex carbon headed ADX drivers from the mid-90s). Nike has gone a step further in increasing the MOI of the driver head by squaring the shape.
The triangle or horseshoe shape that characterizes many of the new putters is an example of increasing the putter head's MOI, resulting in less twisting of the putter head and more accurate putting. This same concept can be applied to driver heads.
The MOI of a golf club can be measured from heel to toe (Izz); from sole to crown (Ixx); in the droop direction (slope of the crown to the toe, Iyy); and from around the hosel (Ihh). In any of these measures, we are talking about distributing mass so as to increase the clubhead's inertia, or resistance to twisting. The Izz measure, heel to toe, cannot exceed the new USGA limit of 5900 g-cm2 (which is an inertial load metric, not a standard measure of mass).
Nike asserts that the square shape allows for optimum placement of the inertial load as measured from heel to toe. The new Sumo2 driver has a square shape, a carbon crown and titanium body and face. The square shape allows for distribution of mass in the corners, mass that was removed from the crown by substituting carbon for titanium. The square shape of the new Callaway FTi and triangular shape of the new Titleist 907D1 drivers address the same distribution of mass.
The Sumo2 has an MOI of 5300, which reduces the yardage loss on mis-hits and may result in longer, straighter drives on good hits. The high MOI makes the club more stable at impact, so if you hit if off center, you won't lose distance. These mis-hits should also be straighter, resulting in fewer out of bounds shots.
Tom Wishon points out that for the MOI to deliver more forgiveness for an off center hit of a distance increase of 5 yards or more, the MOI has to be increased by 1000 g-cm2 or more, [assuming that the driver's specs fit the golfer's swing]. He claims there are other drivers on the market that have an MOI in the area of 4500 to 5000 g-cm2, which, if matched to the golfer re: shaft, loft, face angle, etc., are likely to perform as well on a mis-hit drive as the new Sumo2, FTi and 907D1.
I don't agree with Wishon on this point, if only because 1000 g-cm2 is a whopping 20% of the total. Why would Nike trumpet the superiority of the Sumo2 with an MOI of 5300 when the original Sasquatch had an MOI of 4650, exactly in the area Wishon references?
This is a good topic for a Golf Forum.