## Tuesday, November 15, 2011

### More MOI Matching Questions Answered

I’ve received a few more MOI Matching Questions.

RON from Philly asks about how MOI matching would pertain to what he is learning with John Erickson’s ‘Advanced Ballstriking’ swing theory (www.advancedballstriking.com)

For those who don’t know, Erickson believes in having heavy equipment. I do not disagree, although I think it’s probably a little too heavy for my tastes. I think his swingweights for his long irons are about D-4, then mid-irons about D-6, then short irons are in the D-8 to E-0 range.

Essentially, Erickson is applying some of the same principles in his own set as done with MOI Matching. He’s doing it by his own feel and with the help of a swingweight machine. However, MOI Matching is more exact and easier to accomplish if you have the machine.

If you are in ABS or any type of swing theory, you can use MOI Matching just fine. The clubs can still be quite heavy, it’s just making sure that the amount of force required to swing each club is the same. I used moderately heavy equipment and my optimal MOI with the irons is probably around 2,725 to 2,750. I would imagine Erickson’s optimal MOI is in the 2,800 – 2,825 range. Could be even higher.

ETHAN from London doesn’t quite understand the difference between swingweight and MOI because the difference between weight and mass is confusing.

Let’s break down swingweight and then really break down the term ‘force.’

Swingweight is the effective weight of a club when you are swinging the club. Force is mass multiplied by Acceleration (F = M x A)

Weight is the amount of gravitational pull an object has. Mass is the amount of matter an object has. Let’s say you have a 200 pound man on earth, fly to the moon. If he goes to the moon, he may weigh less than a pound. That’s because the gravitational pull from the earth to the moon has changed. However, his mass is still the same.

Where this applies to the golf club is that I can have two six irons that have different mass, but the same swingweight. I can take one of the six irons, install a heavier shaft and backweight it to make it the same swingweight as the other six iron with a lighter shaft and heavier clubhead.

But, that’s not all. The acceleration component also comes into play. And for the purposes of the golf club, we are talking about the ‘loading’ and ‘unloading’ of the shaft. Somebody like David Toms with a full sweep release accelerates the club differently than John Senden who has more of a snap release.

So a big part of finding the right MOI is to fit the MOI measurement to the golfer’s swing and how they accelerate the club. Somebody like Toms would probably want a lower MOI than Senden.

JIM from San Jose wants to know how the process of MOI Matching is done after the golfer is fitted for their MOI measurement.

Once the golfer has been fitted, you take the club and measure it on the machine. If you hit a 6-iron at 2,750 kg/cm2, we now want the rest of the irons at 2,750 (within 5 kg/cm2)

Typically, weight will be added to the clubhead. Most MOI fitters prefer to use hosel weights. The hosel weights actually go into the tip end of the shaft, then the fitter can just epoxy them into the shaft so they don’t come loose. What most fitters do is that they will dry assemble the club, put it on the MOI Machine and measure it. They will have to add so many kg/cm2 to account for the grip, ferrule and epoxy. So a dry assembled club at 2,720 the clubmaker may add 20 kg/cm2 in order to account for the grip and epoxy.

One can simply use lead tape as well. But, the cosmetics of lead tape are not as good and the lead tape tends to erode over time which will affect the MOI measurement. I have found that one 2 inch strip of high density lead tape equals about 30 kg/cm2. Thus, if the lead tape erodes, it can throw off your MOI measurement too much.

From there, clubfitters typically add about 70 kg/cm2 to the hybrids, 100 kg/cm2 to the fairway woods and 150 kg/cm2 to the driver. Thus, if your irons are matched to 2,750 kg/cm2, then your hybrid should be at 2,820, your 3-wood and 5-wood at 2,850 and your driver at 2,900.

CRAIG in Albany, NY is worried about the 3/8” club length increments over the traditional 1/2” increments

The good news is that it is NOT mandatory to use 3/8” increments in order to MOI match clubs. The reason why some clubmakers do that is that the clubheads get heavier as the iron club gets shorter. Thus, a 9-iron clubhead will weigh more than a 3-iron clubhead. Companies typically make the difference in weight in increments as well. MOI fitters have found that the 3/8” increment makes it easier to MOI match. And in reality, the difference in traditional increments versus MOI matching increments is unnoticeable. However, if a person wants to keep the clubs at ½” increments, it can be done. It may require some lead tape along with the hosel weight to make it exact.

STEVE in Des Moines, doesn’t understand my statement of clubmakers saying that MOI Matching is superior to frequency matching when they measure two different aspects of the club.

Frequency Matching is the measurement of the stiffness of the shaft. It’s done by measuring the cycles per minute (CPM) of the shaft when the shaft is deflected. MOI Matching measures the amount of force required to swing the club.

So yes…they are very different aspects.

I’m not saying I know for sure that MOI Matching is superior to frequency matching, but I understand the idea.

The main reason is that I can hit a shaft that is way too weak (and too stiff) quite well. In fact, I had an Adams Speedline driver with a shaft that measure at a Senior flex that I could hit extremely well for a long period of time.

The problem is that if I did not time the release of the clubhead properly, it would usually kick the shaft too soon. I believe that Dr. Sasho Mackenzie’s measurements are that for every 1 centimeter of forward shaft deflection, the face closes by 0.7*. That’s why we tend to hook shafts that are too weak. The shaft kicks too early for us and the face closes too much and that forces our path to be inside-to-out with relation to the face.

However, if MOI Matching gives the golfer the club with the same amount of force required to swing the club, the golfer is now swinging clubs that require a similar amount of acceleration. When that becomes consistent, it’s now easier for the golfer to release the club consistently. Instead of having to release one club at a different time than another club.

The problem with frequency matching is that graphite shafts typically come in quite weak as far as shaft flex goes. For instance, I ordered a Harrison Saga X-stiff shaft and it measured in at ‘stiff’ flex. I had a Fujikura shaft labeled at ‘stiff’ flex and it came it at Ladies stiff flex.

The way to combat that is to carefully trim the proper amount from the tip end and butt end of the shaft and measure the CPM. The problem is that it may require trimming more from the butt end or the tip end then you want. The more you trim from the tip end, that lowers the kick point…which will launch the ball higher with more spin. More you trim from the butt end, the kickpoint is moved up higher and that will launch the ball lower with lower spin. Therefore, by frequency matching, you may find it difficult to find a shaft with the flex you’re looking for and the shaft profile you are looking for.

With MOI Matching and the Harrison ShotMaker insert, I think it allows more shafts to ‘come into play’ and if a shaft is too weak, the ShotMaker Insert can stiffen it up a bit and cut down the spin while the MOI matching makes it easier to consistently time the release.

3JACK

Brophy said...

Do club lies get adjusted to account for the adjustment in clublength if you use 3/8 increments?

Rich H. said...

I would imagine that the lie angle can stay the same.

1/2" of shaft length = 1 degree of lie angle.

What you do is you find the 6-iron length and lie for you and then go 3/8" from there.

If you do that, you'll find that your lower lofted irons are *slightly* shorter.

You'll also find that your higher lofted irons will be *slightly* longer.

For instance, let's say you are fitted for a 38.0" 6-iron. If you use 1/2" increments...your 3-iron will be 39-1/2" inches long. If you use 3/8" increments...the 3-iron will be 39-1/8" long. The difference is only 3/8". That's not even the equivalent of 1* of lie angle.

Of course, if you feel you need to bend the lie angle...you can. But, I don't see a reason to bend it more than 1*.

3JACK

NJ2281 said...

Couple points of contention...the Harrison Shotmaker does not affect shaft flex and I think you have some misunderstandings about what the shaft actually does on the downswing. The idea that it "loads" and "unloads" is known to these days to have been a misconception. The shaft indeed flexes from the transition to the downswing with a high enough SS, but it simply wants to return to a being a straight line rather than "kicking" forward like you suggested. I thought the "loading" and "unloading" myth had been dispelled for some time now.