Tuesday, December 17, 2013

MOI & Balance Matching FAQ's - Part III

Doherty states in his MOI Balance Index Spreadsheet that he was able to change his club path with the Balanced clubs. Is this really possible?
I do not believe that this is really possible.

For instance, if a golfer has a path that is -4° left of the target I do not see it suddenly changing to +2° right of the target.

At least I do not believe that Balancing a set of clubs is directly related to the path. I think that MOI matching helps the path become a little tighter in dispersion, thus the smaller impact dispersion when clubs are properly MOI matched. For instance, I feel a golfer whose path ranges from -3 to -9° left with a swingweight matched set of clubs may go to -3 to -6° left with MOI matched clubs.

Mind you, I have no actual evidence of that. However, I have good evidence that impact dispersion greatly improves with clubs that are properly MOI matched. Thus, I am theorizing *why* that is.

Doherty states in his spreadsheet that he was seeing distance gains with his clubs Balanced. Is this possible?

Yes, I believe so. With a 3-iron that is not Balanced, the club already has a low loft. So if we hit it low it will not go as far. And if the club’s mass is more concentrated in the shaft, it’s just going to launch lower.

Conversely, with a PW the club has more than enough loft to produce a high launch and spin ball flight. With the club’s concentration of mass more in the club head, the ball will just be launched higher and spin more. With the clubs properly balanced the launch and spin conditions become more ideal for each club.

How much does this really help?

Here’s a Trackman record of Tour averages. Pay close attention to the Max Height column:


The max height for clubs should roughly be the same. But even the Tour players have some difficulty accomplishing that.

The lowest flying club?


We see the 9-iron and PW fly lower than the 7-iron. However, the point is that Tour golfers have to alter their swing mechanics to hit those short irons lower and the long irons higher. From my experience, I feel it is easier to produce lower ball flights than higher. I can easily knock a shot down lower than normal than to try and hit one noticeably higher than normal.

With Balancing the set, the clubs are designed so the golfer doesn’t have to make wide sweeping changes in swing mechanics to hit their long irons high enough and get that penetrating ball flight with their short irons.

How would counterweighting work with Balance matching clubs?

We have to remember that with clubs here are the rules of thumb as far as weight added at certain locations and how it changes the club's MOI:

1-gram to club head = 10-12 MOI points

1-gram to balance point = 5 MOI points

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

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

Let's say we have this scenario here where our 9-iron is assembled and we are trying to reach a target of 2,725 kg/cm^2 and a Balance Percentage of 60%.

balance 3.png
If we add 3.5 grams of lead tape to the head, that will get us to 2,725 kg/cm^2:

Balance 4.png

However, that lowers the balance to 55.18%.

What we know is that if we were to keep the head weight at 284.5 grams, that 60% of that would be 170.7 grams. 

And since our grip weighs 49 grams, that means the shaft needs to weigh 121.7 grams.

In this scenario, if I were to add a 12-gram counterweight, the components would now look like this:

Balance 5.png

Now, that is not at 60%, but we have a +/- 2 % margin of error to work with. 

Earlier you mentioned that you found that counterweights can often be used in the driver, 3-wood, short irons and wedges.  Why is that?
Aerotech, Nippon and now UST with the Recoil line of shafts appear to be seeing the flaws with swingweight and swingweight matching and are now favoring MOI matching.  But, every other shaft company is deeply entrenched into swingweight matching.  And the OEM's that make the drivers, irons, wedges, etc are the same way.  So the way many clubs are designed with swingweight matching in mind makes them a bit more in need of adding shaft weight in order to balance the club.

I will start with the driver.

Generally, the driver is not a giant issue if the club is designed to spec.  But, the typical shaft lengths of a driver are 45.5" to 46" long.  The shaft's weight and Bend Profile may fit the golfer just fine.  But, it's length may present an issue.  The golfer may have way too long of a driver shaft and now their alignments at address are thrown off.  They'll either end up having too little waist bend at address or they will stand further away from the ball to get that waist bend.  Both of which can set off a lot of compensations to be made in the swing.

So if the golfer wants to fit their driver closer to their height and arm length, they will likely need something in the 44" - 44.75" long range.  In fact, Bubba Watson and Adam Scott, two fairly tall golfers, use a 44.5 and 44.75 inch drivers respectively.

The problem is that just trimming the shaft from the butt end will present some MOI issues.  The MOI will become much lower.  Again, that shaft's weight may have fitted you nicely at 45.5" long, but at 44" long the weight and the heft changes.  And if you like the shaft's Bend Profile you will either need to find a shaft with a similar bend profile that is heavier in weight or use a counterweight. 

I believe that OEM's have struggled to make 3-woods with the correct amount of heft.  Your typical driver head weighs about 200-205 grams.  Your typical 3-wood head weighs about 207-212 grams.

But, the typical driver is 45.5" long while the typical 3-wood is 43" long.  That's a giant difference in shaft length while only having about a 7-gram difference in head weight.

The normal head weight discrepancy in *irons* is 7-grams.  But, irons are only in 1/2" or 3/8" shaft increments.  Here we have a 7-gram increment from teh driver to the 3-wood, but a 2.5" shaft length difference.

The typical adjustment made is that the golfer will use a similar shaft to their driver, but about 10-grams heavier.  I just do not believe that the difference in weight makes up for the 2.5" shaft length difference (or even a 1.5" shaft length difference).

The issue with short irons and wedges is that virtually no matter how heavy of a shaft you use, the shaft will not be heavy enough once it is trimmed.  I purchases a 138 gram wedge shaft, the heaviest I could find, and after trimming it only weighed 110 grams.  And I needed a 122 gram shaft weight.  The same with the shorter irons, except you can get away with using less weight in the counterweight.

In the end, I think this is something consider if a golfer is seeking the ultimate in club fitting and trying to figure out why some clubs either do not feel or perform quite like other clubs in their bag.  And I really think that it can provide a giant benefit to golfers looking to hit their driver better if they are willing to patiently try out different scenarios.


1 comment:

Rusty Ryden said...


Testing for path change by changing weight is something I do during fittings. Most golfers are sensitive to weight and it can create large change to some. However.... understanding that weight will change you swing, especially the lower half of the downswing, I can adapt to almost any club you hand me by waggling it Duffner like, so I know how it is going to 'pop' on me. That does not mean I would like to play that club, but I can hit most on first swing. A skill developed as a fitter.

Back to the reason I commented. Testing for path with radar is not easy. I have found it is best done on a range mat. First, the ball placement is consistent and that means the ball to radar head relationship remains constant. Next, the golfers alignment is guided by the mat. That is critical when looking at path. Radar cannot see poor alignment. If the golfers alignment is inconsistent, looking at path with radar is useless. It is not an easy test and on the dirt I find it is nearly impossible.

I would be interesting in your self test impressions of weight change. Get some lead tape and wrap it around you 6i hosel and see what happens.