Set Make Up by Moment of Inertia

I really need to spend some time talking to you about moment of inertia or (MOI).  A year or two ago I wrote an article for GGM on moment of inertia of the club head and of the club.  Many individuals came into our store scratching their heads and wondering what the h- - l I was talking about.  Since then we have done a lot of experimenting with MOI in building sets of irons.  Half of our staff is playing sets setup by MOI rather than swing weight or traditional ½ inch incremental length changes.

The Moment of inertia of an object is how hard it is to get the club around.  Some call it the heft factor.  It is how easy or hard it is to get the mass of the club moving and accelerate it to the ball.  In the survey we use when custom fitting an individual for clubs, one of the questions we ask is, “What iron do you like the most?”  The majority of individuals pick the 7 iron.  When asked what club they would throw away most pick the 3 iron.  Much of the reason individuals pick the 7 iron is because they like the way it ”feels.”  Most dislike the 3 iron because they “can’t hit it, and don’t like the feel.”  Well, what if we could make the 3 iron “feel” the same as the 7 iron?  For that matter, what if we could make every iron in the bag feel the same as the 7 iron?  We can.

The MOI of a club can be altered by changing the clubs length or weight.  In experiments done here at Pat Ryan Golf we found altering the length of the club was by far the most plausible way of changing the MOI of the club.  Altering the weight of the club may turnout to be the better way of establishing the MOI of the club, but it would be very difficult to build sets this way since club heads come only in a standard weighting. 

When we set up a set of irons by MOI we first find out which iron the individual likes the best, then base the set on that iron.  When building a set this way it is important that the weight of each component be correct.  Every head must be spaced 7 grams apart.  Every shaft must weigh the same and every grip must be weight matched.  Once the correct weights are established then the shafts must be individually cut to the proper length.  All loft and lie angles must be then set correctly for the individual’s needs.  It is additional work, but the results we are getting seem to warrant the effort.

Why go to this effort?  What are the benefits?  The benefits are a better feeling club and a more accurate shot.  There is also the good possibility of more distance.  Most research on MOI has been done on drivers rather than irons.  Below is a chart developed by Howard Butler.  Howard is well known for his knowledge and research.  He has written numerous articles for Golf Tips Magazine.  The chart is showing the change in moment of inertia and shot carry when the only change made to the club is it’s length.  If you look closely you will see the carry distance does not increase when length is added.  It increases when the length is reduced.  People, please understand each time you watch and infrommercial or read a golf company’s ads you are not reading fact.  You are listening to, or reading a sales pitch.  This chart shows the truth. 

FACT:  Added length does not mean added speed.  You will not hit a longer club further with the same effort unless the longer club has a lighter shaft or head

FACT:  Adding weight to the head will slow the club down giving you less distance.

FACT:  Swing weight is only feel.  It shows a relationship of weight and has nothing to do with head weight.  The swing weight of your club is as important to your playing great golf as the temperature of the grass.  Bobby Jones’ irons varied in swing weight from B-8 to D-0 and he played pretty decent golf.

I’m starting to sermonize and am getting a little off the subject.  If you have not been fitted for your clubs, or have not sat down and discussed what a qualified clubfitter could do to improve your game with the equipment, you are not playing your best golf.  Through the knowledge we have today a Pat Ryan Golf can be very creative in building you a set of clubs which you can swing easier and better than you present set.  Find the iron you like and get a set built so they all feel as good as it does.