## Monday, December 16, 2013

### MOI & MOI Balance Matching FAQ's - Part II

In part II I will go over the FAQ’s involved with ‘MOI Balance Index’ often referred to as ‘balancing’ clubs.

What is MOI Balance Index?

MOI Balance Index means that the clubs are MOI matched *AND* the static weight of the components of the club (shaft, grip and head) are in the same proportion. The concept of MBI was developed by an engineer named Monte Doherty. He created an extensive Microsoft Excel spreadsheet to help determine MBI. It not only accounted for the weight of the components, but the Center of Gravity of each component.

Have you ever heard of the ‘balance point’ of a shaft? If so, Doherty’s spreadsheet accounts for the balance point of the shaft as well as the balance point of the grip and the type of head (driver, fairway wood, hybrid, muscleback iron, player’s cavity back iron and Game Improvement iron). Between that and the weights of the components, he created a MOI Balance Index number. The number ranges from 0-100. In reality, the number will range more from 30-70.

I don’t understand what you mean by ‘weight of the components being in the same proportion. Can you explain?

Sure.

Here’s a table of the weight of the components of a set of irons that are swingweight matched.

What many golfers don’t realize is 2 things:

1. Head weights gets progressively heavier as the club has more loft.
2. Shaft weights (trimmed) get progressively lighter as the club gets shorter

Clubs have been designed this way since the beginning of swingweight. When you trim a shaft, the shaft’s static weight becomes lighter (less shaft = less weight). So in order to counter those shafts getting lighter, OEM’s make the heads heavier as the club gets shorter.

However, that causes the proportion of the weight of the clubs to change. When we take the shaft + grip weight and divide that by the head weight, we see dramatic differences. The 3-iron percentage is at 65.1% and the Pitching Wedge percentage is at 51.1%.

So, with ‘balancing a set of clubs’, the percentage would be roughly the same. Let’s say we wanted to match everything to our 6-iron (58.5%), the table would look something like this:

Why is Balancing the set important?

It’s certainly not mandatory to balance a set of clubs. However, the main benefits are launch and ball flight. Provided that you are fitted for Balancing a set of clubs, the concentration of the club’s mass will be roughly the same.

In this set that was not balanced:

We have a 3-iron where there is a higher concentration of the club’s mass in the shaft (65.1%) than with the Pitching Wedge where the concentration of mass is more towards the head.

Now, let’s go back to our example where we want to use the 6-iron’s Balance Percentage (58.5%).

The 3-iron (65.1%) will have a higher concentration of its mass in the shaft. That will produce a lower launch and spin than the golfer is fitted for. And the issue with the 3-iron is that it already has a low loft and does not need to launch lower.

Conversely, the pitching wedge (51.1%) will have a higher concentration of its mass in the head. This will produce a higher launch and higher spin. But, the club already has enough loft to produce that.

To counter their clubs being un-balanced, golfers (even Tour players) will often alter their swing mechanics to get the long irons up in the air and their shorter irons to have a more penetrating ball flight. With Balanced clubs, that requires less of that altering of swing mechanics to produce your desired ball flight.

Do we Balance all of the clubs or just the irons?

Each club can be set to the same percentage, from the Driver to the Lob Wedge. In fact, I feel that the largest benefit of Balancing the clubs is with the driver because that is the club where launch, max height and spin rate is the most important.

Do I have to use Doherty’s spreadsheet to Balance my clubs?

No.

I find that as long as the clubs are MOI matched you can simply figure out what your target % is and then derive how much the shaft + grip should weigh. You may be off a little, but we have a margin of error of +/- 2%.  Doherty's spreadsheet helps account for more finite details like the Center of Gravity of the components.

Won’t this make the clubs super heavy if both the shafts and head ascend in weight?

No.

If we harken back to our discussion on MOI matching; if we match our MOI in our irons and then measure the swingweight, the swingweight will increase as the club gets shorter. So if one were to use the swingweight method with balancing their clubs, they would find that the swingweight gradually increases. But since swingweight does not accurately depict heft, the heft of the club would not change if clubs are balanced properly and the MOI matches.

So how does one get ascending shaft weights since shafts get lighter as you trim them shorter?

First, we are starting to see to see major shaft companies addressing this issue with equipment. Nippon shafts have made ‘constant weighted’ shafts where the shafts remain the same weight after they are trimmed (margin of error of +/- 1 gram). Furthermore, Aerotech has created a model of shafts called the Player Spec and UST has created the Recoil model of shafts that ascend in weight. I believe that we will start to see more and more companies go in this direction.

However, there are a couple of ways to do this.

For starters, you will need access to Wishon’s Bend Profile software. If you’re being fitted with a 6-iron, which I recommend, it’s likely that the shaft fitted for the 6-iron will be too heavy in the 3 & 4-irons. If so, you will need to find a shaft with a similar bend profile that is lighter in weight to install into those clubs.

From the clubs that require heavier shafts, there are a couple of options.

For starters, one could go into the Bend Profile software and look for heavier shafts with similar bend profiles.

The other part is to add weight to the shaft. Either via a counterweight, an internal shaft weight like the Tour Lock Opti-Vibe or using lead tape to place on the shaft.

Chances are you will likely need to do this with the shorter irons because if the irons are going to ascend in weight you will probably not find a heavier shaft that is heavy enough. For instance, I’ve taken 133 gram wedge shafts that weight 108 grams when trimmed to SW length. And if the SW shaft needs to be 120 grams, then you have a problem.

The best method is to add weight to the shaft, either thru lead tape, a counterweight or the Tour Lock Opti-Vibe.

Do we have to measure the weight of the ferrule, epoxy, grip tape, etc?

For most accurate measuring, yes.

The ferrule will weigh about 1.0 to 1.5 grams.  The epoxy weighs about 0.3 grams.  Grip tape will measure about 1 gram per wrap.  So if you put 2 wraps of tape, it will weigh roughly 2 grams.  With the epoxy and ferrule, we just count that as part of the head's weight.  The grip tape would count as part of the grip's weight.

How does adding weight to the shaft affect the club's MOI?

It depends on where the weight is added.  The closer down the head, the more it adds to MOI.  General rule of thumb is:

1-gram on balance point of shaft = 5 MOI points

1-gram near shaft label (below grip) = 2-3 MOI points

1-gram on butt-end of shaft = 0 MOI points

So, how does using a counterweight work?

Since the counterweight is on the butt end of the grip, it will have little affect on MOI.  IIRC, 1-gram of weight on the butt end of shaft equals about 1/400th of a MOI point.

Tour Lock makes a counterweight called the 'Tour Lock Pro Counterweight.'

They also make a product called the 'Opti-Vibe.'

The Opti-Vibe is *not* a counterweight.

It is called an 'internal shaft weight.'  It is a weighting product that the installer can put into the shaft thru the butt end and then move the weight up and down the shaft depending on how much MOI they want to add.  The further down the shaft they move the Opti-Vibe, the more MOI it adds to the club.

Here's a demonstration:

3JACK