Golf Clubmaking - Moment of Inertia

Swingweight  | Moment of Inertia | Shaft Flex and Frequency matching
		Moment of Inertia (MOI) ‘Moment of Inertia’ or MOI is the buzz word in the golfing world at the moment with nearly ever golfer actually getting confused with what it actually means. MOI is defined as the measurement of an objects ability to resist twisting and all objects have aa MOI though many cannot be measured because its impractical. Golfers are now seeing branded on club heads"Max MOI". Highly sophisticated equipment is used to grade a clubheads MOI and the higher the MOI the more the clubhead is able to resist twisting at impact. The governing bodies of golf have introduced a limit of MOI which is 5900g cm2. I am not aware of any clubs being within 10% of this grading and although manufacturers claim to achieved it, none of these claims to the best of my knowledge have been substantiated.

Higher MOI can be achieved by redistributing the club head weight either at the heel, toe or perimeter of the head. This has largely been responsible for the introduction of the new square headed drivers and many other different shapes to follow.

If the weight is pushed out further from the club heads centre of gravity then the higher will be its MOI and there will be less of an inclination for it to twist if it impacts the ball off centre. The result of this will be for the ball to travel consistently further and straighter because the clubhead remains square to the target longer.

This is all about the MOI of a 'clubhead', the whole golf club also has a measurable MOI in its own right. Knowing the golf clubs MOI enables the construction and matching of entire golf clubs in a set. which will perform uniformly to the same physical effort exerted on each of them. Every golf club will feel the exactly the same to swing.

A made up Golf clubs MOI is defined as the measurement of resistance which the golf club has when it is being swung. So the measurement relates to how a clubhead 'feels' to the golfer when it is being swung. This is similar to swingweighting except swingweighting is a static measurement and MOI is a Dynamic measurement.  

To fit a golf club to a golfer the Club Maker / Fitter needs to ascertain what resistance works the best for each individual golfer, a set of clubs can then be built to that MOI and the golfer will have a more consistent swing because each club will require the same effort to swing.

Finding the Moment of Inertia (MOI) can be done in two ways. First of all we need to identify that 'favourite' club, the one that most consistently performs for you and you 'feel' most at home with. Once this club has been identified we will measure its MOI or swingweight. In the unlikely event that you are unable to identify 'that club' then we will reveal it for you, through dynamic testing using our sophisticated Vector Launch system and Impact markers placed on the face of our extensive range of demo clubs until we identify a club that you can hit consistently well and 'feels' the way it should do for you. Ideally both methods would be used and an average MOI measurement will be obtained. This magic club will then be used as the template to building the rest of the set of clubs to.

This club would be our template club where we match the rest of the set of irons to it, making every club feel like this one.

It is virtually impossible to match the whole set of 13 clubs to the same MOI because Drivers and wedges differ so greatly, so we MOI match clubs in groups i.e. Irons, 3-9 iron, Wedges, PW-LW and Woods, Driver – 9 wood etc.

Most golfers have tried out another club say a demo driver and been sufficiently impressed to actually buy one off the shelf. the club on the shelf looks the same has the same markings as the demo driver you loved so much, it must be the same club. You have a better chance of winning the lottery than getting the exact same driver as the demo you loved so much! This is because of various reasons to long to list so I merely advise that your chances of getting virtually the same 'feel' from the club would be greatly enhanced by having the club frequency and MOI matched.

As you have probably read in our Custom golf club fitting page on this website we start a fitting with a blank piece of paper as everyone has their unique golf swing. When we come to build a set of clubs and as part of the fitting process we identify what clubs would best suit your game. MOI matched golf clubs may not suit your individual golf swing.

GOLFCLUBS4ME golf clubs can be made in 3 completely different ways;

1. Swingweighted matched
2. Constant ball MOI matched
3. Sloped MOI matched

Current teaching encourages reproducing the same golf swing for every club in the bag and to place the ball in the same position in the stance, regardless of what club is being used, ie just inside your target foot heel (left foot for right handed golfers and right foot for left handed golfers). If this is the case a MOI matched set of clubs that are set up for a constant ball position would be ideal and would result in a complete release of the golf club in the same position during the swing.

Many golfers have been taught or shown, to vary the ball position for all their clubs. ie longer irons would be played further forward than the wedges etc. Whilst I do not deride this theory as it is still actually being taught today by some instructors and no doubt works for some people, a 'constant ball position MOI' matched set of clubs would not work for these golfers, as the golfer may find it difficult to release the clubhead at the ball using clubs that are set for a constant ball position. The golfer will need earlier release in the short irons and later release in the longer irons. An adaptation of the MOI would be necessary for this technique to be most effective and this involves 'sloped MOI'. With normal constant ball MOI matching, the shorter clubheads get the heavier quite quickly. 'Sloped MOI' would still make the shorter irons heavier and longer irons lighter but much slower making it a more progressive sloping of the matched set of clubs. 

By having a MOI matched of clubs, if you close your eyes and take a different club in the set, there is no way you would not be able to tell the difference between clubs in terms of how it feels to swing, meaning that you strike will be more consistent as it’s the same swing for every club.

Golf club fitting is based on trying to get a golf club that works for an individuals golf swing. One of the characteristics we look for is how a club feels when it is swung. Some golfers prefer a Heft or otherwise known as swingweighted matched set rather than MOI matched set of clubs, so swingweighted matched clubs can still be built .

Are the pros on tour using MOI matched clubs? If this was your livelihood and you know that it could give you an advantage over the rest of the field, would you use it?

Click here contact Mark for professional custom fitting using the contact form in our retail store www.snakeeyes.co.nz/shop