Q: Ben in simple terms what is MOI?
A: This is a hard one to answer. MOI is a term that is used for more than one description in relation to a golf club. You hear drivers being described having a "higher MOI and easier to hit and more forgiveness", you see putters being advertised as "higher MOI means less twisting at impact", and then you have club makers saying "MOI matched irons mean they all feel the same to swing". I will touch briefly on the first two points of MOI and then try and go a little more in depth into MOI matching of clubs. In very basic terms Moment of Inertia is the measurement of an objects resistance to being put into motion.
Q: So how does this fit within golf clubs?
A: In terms of "higher MOI, easier to hit and more forgiveness" it basically means that at impact, the club will not twist as much, same as with a high MOI putter. With putters you will notice that there is a lot more weight out on the heel and the toe. This will add mass to the outside of the putter and allow the putter to move through impact without twisting. It's kind of like a truck and a car, if you imagine a truck trying to stop with a heavy load, it will take a lot longer distance than a car.
Q: How does this fit in with irons and making them feel the same to swing though a set?
A: When I talk about MOI matching of clubs, I am talking about matching the energy or force required to swing each golf club.
Q: But isn't that what swing-weight matching is?
A: The swing-weight scale was actually invented to try and produce an MOI match. Unfortunately the swing-weight scale only cares about how much weight is in the head of the golf club and does not take into account of the overall weight of the golf club. Swing-weight can be altered significantly by changing different weight grips, where MOI matching is not as influenced by small changes to positional weight.
Q: How does MOI matching feel different to swing-weight matching?
A: An easy example is this. Grab your longest iron and your pitching wedge. Swing them both like a baseball, you will feel that the pitching wedge feels much heavier than the longer iron. What you are feeling is the difference in amount of force required to swing the golf club. With a MOI matched set the difference is subtle and all clubs feel pretty much the same. One of my biggest complaints from clients is that sometimes they pull out a 6 iron instead of a 9 iron and swing it, and because they cannot feel the difference between the two clubs, they tend to overshoot their mark.
Q: So MOI looks to move on from Swing Weighting?
Yes and no. MOI matching does what swing weighting has always tried to do. In the 1920's when the swing weight scale was invented, it was actually trying to replicate MOI. It wasn't until 2004 when we really had the complete range of tools (from Tom Wishon) to measure, calculate and build for MOI.
Q: Does it have much relationship to Counter Balancing?
A: Counter Balancing and MOI don't really have a whole lot in common (well not the way I do MOI matching anyway). Counter Balancing is a whole other subject and is also very subjective to golfer.
Q: So MOI produces a feel for a set of clubs that suits a player. How do you arrive at the idea fit? I hear it's a bit like peeling an onion.
A: More often than not someone has a club in their bag that they find easiest to hit, it's typically a shorter iron (though I had someone whose favourite was a 4 iron!). A favourite club usually represents the club where the golfer feels most comfortable with that club's MOI. We can measure that club for MOI and then use that to build a new set. If a golfer does not have a favourite club, we typically use a 6 or 7 iron after they have gone through a fitting and we determine what the correct length, flex, shaft weight, grip size and head design is.
Q: At what level of handicap does MOI seem to make real improvements to a player's game?
A: It's typically the highest handicappers that see the benefit the most. I've never had a client come back and say "Ben, I cannot hit these clubs", it's always the exact opposite. I have 30 handicappers who can hit a 3 iron like it's a 7 iron. Having said that, it benefits all golfers, I had a 4 handicapper that went down to 1 in about 5 weeks after moving to the MOI set of clubs.
Q: Does MOI apply to all clubs?
A: MOI matching for woods is done differently to irons because of the weights and lengths of clubs. Typically we match woods to your favourite wood and irons to your favourite iron. Wedges are not typically MOI matched as they are used totally different to the rest of your clubs. Sand irons should not be used to take full shots from fluffy fairways they are designed to move through sand with shorter, slow but typically more aggressive swings. The whole point behind MOI is to provide a smooth and consistent swing. Swing weight matching cannot do this, if you are using a different force to swing each golf club, then you will logically put a different swing on each golf club. This makes the game harder than it needs to be.
Time and our understanding of practical applications of science move on. Yet it is the simple task of feeling what is going on with our golf clubs in our hands which give proof to the puddings worth. Anything we can do to produce feel to the golfer is worth the endeavour of a little trial and error. All of the fitting methods in Part One and Two have been attempts at just this, the endeavour to feel more and to tune the effort we put into our swings more precisely.
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