Is there an error in the Mizuno MP-18 SC MPF calculation? The VCOG CF is considerably higher (?) than everything else, and the MPF is lower than the straight MP-18. Seems to me like it should be higher.
Side bar: what exactly is VCOG CF?
No error in the calculation. I went back and triple checked. The explanation is difficult to convey, but the link below will explain, partially, how the correction factor works. One thing it does not detail is the when the rearward cg is so narrow or short, even if the basic vertical is below .840 (.839 on the MP18 SC), the actual vertical will be negatively effected and actually be higher than the basic vertical. Does not happen often on #6 irons, but in this case, based on Ralph’s formula, that is the way it is.
The correction factors is also explained the original MPF book. Ralph states int he book that the correction factors were developed solely by him based on his experience and testing. It’s intended to fairly represent an unfavorable change in Playability, and proven to be an adjustment that more favorably represents the actual Playability.