Club Weight Feel - Swingweight vs MOI?
Many, if not all of you, are familiar with the term "swingweight" as a measure of how heavy golf clubs feel, and how this weight feel affects the performance of golf clubs. It has been an important golf club fitting parameter for many years. There is growing evidence, however, that there may be a better way to build clubs so that the weight feel is truly optimized for players - MOI, or Moment of Inertia matching. As discussed below, MOI Matching is old and new.
Much of the information in this section comes from a note from the Dave Tutleman web site, and also a note from Richard Kempton, an experienced clubfitter in the United Kingdom.
In the early 1900s, clubmakers building clubs for professionals by matching clubs based on the product of the head weight and the square of the length of the golf club. So the longer the clubs would be, the lighter the heads would have to be for the clubs to be "matched." Clubmakers at that time found that matching clubs this way took a lot of calculations and time.
In 1930 Robert Adams, a clubmaker, invented the swingweight scale. It is a balance between the head weight end of a club versus the grip weight end of the club, using a 14 inch pivot from the grip end of the club. Around 1945 Kenneth Smith bought Adam's rights to the swingweight scale. The most often used version of the scale uses a 14 inch fulcrum. Adams developed a letter scale for measures of swingweight. Higher letters relate to higher swingweights, and higher numbers within a letter group relate to higher swingweights. Men's clubs purchased in stores often have swingweights in the range of D-1, while women's clubs purchased in stores often have swingweights in the range of C-6.
In terms of swingweight higher head weights, higher shaft weights, and lower grip weights lead to higher values of swingweight. So, for example, you could have a club that has a D-1 swingweight, add 4 grams of weight to the head and 10 grams of weight to the grip end, and it would still be a D-1 swingweight. Swingweight is a static measurement of the weight feel of a golf club.
Within the last 10 to 15 years, another method of measuring the weight feel of a golf club has been used primarily by custom clubfitters. This method is MOI (moment of inertia) matching. The MOI of a golf club is a measurement of how much force it takes to put the club into motion around the grip end of the club. It has units of mass times length squared - interestingly, the same units clubmakers used in the early 1900s for their club matching! Now, though, there are devices available that can easily and quickly measure the MOI of a golf club.
MOI is a measure of the dynamic feel of a golf club, while swingweight is a measure of the static feel of a golf club. The relationship between the two, if you look at a set of irons, is that - for a set of clubs that are MOI matched - the swingweights of the clubs will increase as you move from longer to shorter irons.
There is a lot of evidence that for many players MOI matched clubs play better than swingweight matched clubs. I mentioned Richard Kempton earlier. He noted that he now does MOI matching for all sets he builds, and for 500 sets of clubs he has not had one player say he did not like the feel of the clubs. In the last 2 years I have done about 20 sets of clubs using MOI matching, and 1 person said he did not like the feel of them (I rebuilt this set to constant swingweights).
Usually the right MOI for a player's driver is different than that for fairway woods, and the MOI for a set of irons also differs from the woods. MOI matched irons have a similar dynamic weight feel throughout the set. What is typically done in a fitting, say for irons, it to find the best MOI based on testing with say a 6 iron, and then build the irons to that MOI throughout the set. Sometimes, a difference in head weight of as little as 2 grams makes a significant difference in club performance.
MOI club matching is probably something you will hear more of in the future. While not likely to be available in OEM golf stores, it is an option that is available from many custom clubfitters and worth considering.
