More Recent MOI-Matching Experience

Dave Tutelman  --  March 9, 2008

You may have seen and read my articles about my early experiments with MOI matching, which were originally posted on the newsgroup in 1995. I have had some more recent experiences that are also worth recording. Here they are...

August 1998

In the summer of 1998, I had an opportunity to try another set of MOI-matched irons. The occasion was a visit with family in San Diego, and a round of golf with Dale Winstead, whom I knew from but had never met in person. I had not brought my sticks, but Dale had an extra set that he had made a few years before. He lent me his older set. I documented the round elsewhere, but let me copy a relevant excerpt from that article.
I did have a "clubmaker moment" in all this.  The clubs Dale brought for me were a set he made for himself several years ago, and has since replaced.  They were Golfsmith Square-Toe Blades on Dynamic Stiffs.  I found that, while I was hitting the short irons fine, I was pull-hooking the middle and long irons.  Consistently.  Disastrously (remember that kikuyu rough).  On the fourth tee, Dale mentioned that he had built them moment-of-inertia matched.  I said, "Then I know how to hit them," and proceeded to hit a long 3-iron with a bit of fade.  From then on, I was fine with the irons.  The secret was that I knew MOI-matched clubs need to be played from the same point in the stance.  I was hitting the PW and 9i fine from the middle of my stance, so I started playing all the irons from there.  It worked!
This definitely confirmed a few things for me:
  1. MOI-matched clubs do depend on playing the ball from the same spot in your stance for all the irons. If you, like me, gradually move the ball from mid-stance in short irons to forward in the longer clubs, you may have some trouble with constant MOI across the set.
  2. If I MOI-match clubs to a favorite (namely a short iron, which I play from the middle of my stance), the set will be a disaster for me.
Unfortunately, the logical next step took me almost ten years...

March 2008


I was not that strongly motivated to continue experiments with MOI matching for my own clubs until now. By this time, Tom Wishon had been pushing it for several years as "the answer", and GolfMechanix had been making an MOI pendulum for doing the matching -- and had just introduced their MOI "speedmatch", which operated by making the club a spring-driven "pendulum" that could measure MOI directly. But my interest since 1998 had been mostly academic and analytical; I already had something that worked, and I knew the problem of MOI-matched clubs with my swing.

In 2007, I had achieved the ripe old age of 66, and was beginning to feel it. One aspect of my golf game in particular felt it -- my hands. I am known as a good iron player for my age, particularly short irons that I hit high with lots of spin. But I was hitting those clubs from the middle of my stance or even farther back, with a decidedly downward blow. My golf buddies were used to seeing me take a "beaver pelt" divot to produce those shots. And my manual joints were beginning to feel it between rounds. Then the relevance of a few seemingly unrelated facts struck home:
  • Most modern teaching of the swing calls for the ball just inside the left heel (for a righty like me) for all the irons.
  • All the best tour players play this way.
  • Some of the better TV color commentators point out how Tiger (or occasionally some other very good player) takes a pretty shallow divot.
Putting these facts together produced an "aha moment". These guys hit perfectly good iron shots with a shallow divot. I take a deep divot to product good short iron shots. I play those shots from the middle of my stance, which results in:
  • Hitting down for spin and solid contact.
  • A big divot.
  • Knuckles that hurt.

Suddenly I felt motivated to learn to hit using the modern ball placement, which should result in a shallow divot. So I briefly gave it a try with my current, swingweight-matched irons. If you've been with me so far, you probably know where this went. I had too many less-than-solid hits with my shorter clubs. Too many tops. Too many fats when I compensated for the tops. Even my good shots were too high.

At this point, something clicked. (Well, I knew it all along, but refused to admit it to myself.) I needed a set of irons that were MOI-matched, but matched to a swing bottom near my left heel. My previous experiences with MOI matching were matched to a swing bottom in the middle of my stance, where I played my favorite clubs, the short irons.

Let's look at some implications of this decision:
  1. This is not a match to my favorite club. It can't be! The goal is to allow me to hit short irons from my left heel. I now hit short irons -- my favorite clubs -- from the middle of my stance. So I must necessarily build clubs with a different feel from my favorite.
  2. The clubs should have a higher MOI than any of the MOI-matched sets I have used so far.

Fitting and Constuction

Component selection: It was easy to decide which components to use. I already owned a set that I liked, whose specs were almost identical (length, loft, lie, frequency, swingweight) to the clubs that are currently in the bag (John Ford "Impacts"). They had steel shafts, with plenty of room for the tip weights that I would need. They had a really good pedigree; they were my favorite Tom Wishon design. No, not a TWGT component. They were the original Jetstream, from TW's days with Golfsmith. I've always been very fond of this head, and welcomed the opportunity to play with them again. And, given Tom's evangelism for MOI matching, it is appropriate that I use one of his designs for this experiment.

Fitting: The next step was fitting myself for MOI. I wanted to let this be a test of the MOI-matched concept for my swing. So I decided to fit the 4-iron, the longest club I hit well enough to carry -- and blindly build the rest to the same MOI. I took the 4-iron (and my current in-the-bag 4-iron) to an open field with a shag bag and a roll of lead tape. I played with the Jetstream weight while I left the Impact as a control. I seemed most comfortable (actually most repeatable) with the Jetstream a couple of swingweight points higher than it was originally. So I resolved to MOI-match the set against the heavy Jetstream.

As a check on this -- and to reassure myself that MOI matching might work for me -- I repeated the 4-iron procedure with the PW, applying lead tape to find the best heft for me. Unlike my usual pitching wedge from back in the stance, I did all this testing from inside the left heel. When I got back to my workshop, the swingweight scale and the computer told me the two clubs were pretty close in MOI. They were less than a swingweight point away from a perfect MOI match.  So I felt I knew the MOI that would be good for me.

Construction: I use a swingweight scale to heft-match clubs. In order to MOI-match them, I slope the swingweight by 1.3 points per inch of length. (For more detail on this, see my article on the subject.) Here is the table I worked from, and the final results:

Club Swingweight
3-iron D2 D3 D3.2
4-iron D1.7 D3.6 D3.5
5-iron D1.5 D4.3 D4.2
6-iron D2.5 D4.9 D4.7
7-iron D2.3 D5.6 D5.3
8-iron D2.3 D6.2 D6.2
9-iron D2.3 D6.9 D6.7
PW D6 D6.9 D7

  1. The original set was matched at D2 point. Except for the PW. Which brings us to...
  2. The heads came from the foundry weighted assuming a shorter PW than 9-iron. The PW continued in the usual 7-gram progression. I like my wedges the same length as the 9-iron, so I had a discontinuity in my heft-matching. The MOI-matched set was an opportunity for me to fix that problem.
  3. I used lead tip weights for most of the work. I used a bit of lead tape on three clubs: two because I needed more weight than the 7-gram biggest weight I had, and one because I only needed to add 1 gram and my smallest weight was 3 grams.
  4. For those of you who are more familiar with MOI units, the set was matched to a range of 2800 to 2813 kilogram centimeters squared, or 434,000 to 436,000 gram inches squared.
  5. Comparing this with previous MOI-matched sets I had tried, this set is almost 100 Kg-cm2 "heavier". I guess the lesson is completely unsurprising, given everything I've preached for years. It isn't enough to MOI-match the clubs; they must be MOI-matched to the golfer.
When I carried the finished set to the car, they felt tangibly heavier than my old irons. (Just my imagination? Maybe. This was hardly a controlled experiment, and in fact the total weight of the set was only increased by about 2%.)

Driving range

March 9

It is still pretty cold and windy in New Jersey, but I couldn't wait to try them out. Went to the driving range. (The same range where I tested my first MOI-matched set, and only a couple of stalls away from that test.)

The results were very encouraging. I don't remember any range session with irons -- not any -- that saw a greater percentage of solid hits. Except for the 3-iron (which I still can't hit well even if it's MOI-matched), I had only one less-than-solid hit from a whole bucket of full swings. It's taking a while to get the direction right; I am tending to pull them. But I was doing better by the end of the session. My attempts at trajectory control (knocking down the ball from the back of my stance) will take quite a bit more work.

The most satisfying things coming out of the range session were:
  • Consistency of solid hits across the set. That suggests that modern ball placement is on the right track.
  • The delightful feel of hitting a good iron shot without my hands feeling the concrete under the rubberized mat. That suggests that I am getting the shallow divot I was hoping for.

On-course practice

March 10

Shark River GC, one of our Monmouth County parks department courses, is open during the winter, but just temporary greens. Not worth it for around-the-greens practice, but it's a great bargain for on-course swing practice. Only $12, it's a nice, tight course, and it's generally pretty empty. There was only one other person on it today, and we kept out of each other's way. When I'm just practicing alone like that, I'll hit a second ball if I'm not happy with the shot -- or sometimes even if I'm very happy and just want to see if I can hit two in a row like that. Perfect conditions to try out a new set of irons.

First the bad news: I didn't have as high a percentage of solid hits as I did at the range. Not surprising, but disappointing.

Now the good news:
  1. First and most important, the solid hits were still abundant. I hit these clubs better from off the left heel than I did my old set from a variable ball position. Definitely more of the shots were solid than my usual round.
  2. Second, and almost as important, I had flat, shallow divots. Only two big divots all day. They were not as big as my usual big divot. And both those shots were terrible swings anyway. So that part of the experiment was a raving success.
  3. As the round progressed, I got better at directional control. I got rid of the big, uncontrolled pulls. The back nine saw a lot of straight shots, and roughly equal misses left and right. (And very few of those misses were big -- like enough to miss a fairway.)
I still don't know if my distance and spin are as good as the Impacts, especially for the short irons. The longer irons (4i and 5i) are great. I got huge hits with the 4-iron any time I made a decent swing.

And I still don't know how it will hold up when I'm counting score, instead of a practice round with unlimited mulligans. Maybe I'll get out for a round of actual golf tomorrow.

First round on the course

March 11

It was a very nice day, sunny and about 50F, so I did a walk-on at Pebble Creek. I tried to use the irons whenever they might make sense. In practice, this meant that I never pulled out the 7-wood; always used the 4-iron for those shots. And there were a couple of shots that I normally would have used a 5-wood, where today I hit the 4-iron.

In general, I was pleased with the set. But it wasn't such a clear winner that I've made my decision yet. I'm going to play -- and report -- another round or two. Detailed impressions:
  1. I had more clean hits with these irons than my previous set. But the margin was not as great as the practice round yesterday, and nowhere near what I did on the range. Is the honeymoon nearly over? Or does the pressure of having to make a shot drag the performance down almost to that of the Impacts? We'll play a few more rounds and see.
  2. The heavier pitching wedge is a big plus, both for full swings and touch shots. That may stay in any event, But...
  3. I think I may have lost some distance with the shorter irons (say, 7-iron and up). The 5-iron is as long as the Impacts, and the 4-iron is probably a little longer. But the 9-iron in the MOI-matched Jetstreams is only a bit longer than the PW was in the swingweight-matched Impacts. This is not necessarily a bad thing. But it is a potential difference that needs to be understood, if it continues to show up in future rounds.
I'd like to look at point #3 a little closer. If more experience proves that the effect is real, I can think of a few possible reasons:
  • When I play the ball from farther back in the stance, I de-loft the club. (Actually it's reduced angle of attack rather than reduced loft, but either way gives a lower launch and a longer flight.) Since I play the long irons of both sets from the same place in the stance, they would not be affected as much. (I consider this the most likely explanation.)
  • The heavier heads reduce the clubhead speed. They probably do a little bit, but my other investigations of total weight vs distance don't support nearly this much distance loss.
  • The Jetstreams are more sole-weighted than the Impacts, which may explain the higher flight that I observed, along with the decreased distance. But I rather doubt this is the cause. The higher flight and shorter distance affected the short irons but not the long irons. And the Jetstream long irons have an even more lowered center of gravity than the short irons.
So, if there really is a loss of distance, I may have to decide whether it is a price I am willing to pay -- or fix.

More experience

March 12-15

I've played another round and had several more practice sessions as well. My conclusions have not changed much:
  1. This set meets the original motivating goal of being able to play the ball just inside the left heel with all my irons.
  2. I am indeed taking a more shallow divot with this ball position, which is a good thing.
  3. The clubs feel better. The most important contributing factor is probably the shallow divot.
  4. My ball striking is a lot more reliable than my swingweight-matched set in practice sessions, but only marginally more reliable on the golf course. Still, marginally is better than nothing.
  5. I have lost some distance on my short irons.
The last two items call for some further explanation:

#4. Ball-striking - I understand why my ball-striking would be worse on the golf course than the range. I'm no longer just focused on hitting the ball. I'm also worried about hitting a target and, probably more important, not hitting into trouble. The pressure is bound to affect performance.

What I do not understand is why the difference between the new and old sets is greater on the practice tee than on the course. A few tentative speculations:
  • I'm still getting used to the set. Under pressure, I make a swing more appropriate to the older set. (This is plausible.)
  • Hitting down to the middle of the stance is inherently more reliable than trying to catch the ball at the bottom of the swing arc as I do with the new set. (Possible, but I doubt it. I am still more reliable with the new set than the old, just not as much so on the course.)
  • I am not sufficiently familiar (or maybe not comfortable) with the distances, so I may be clubbing wrong. Which brings us to...
#5. Distance - There is no doubt that I have lost some distance on the short irons, and none at all (maybe even gained some) on the long irons. As far as I can tell with this brief experience:
  • The 4-iron is at least as long as my other set.
  • The 7-iron is almost a half-club shorter.
  • The PW is about a full club shorter.
The more interesting questions are why, and what should I do about it.

As for why, one possibility that the club is "de-lofted" when I play an iron from the middle of my stance. Another possibility is the lower clubhead speed due to a heavier head. Let's look at both these theories. I ran some simulations using Max Dupilka's "SwingPerfect" program. I used the weight and length of my PW in the two sets, and compared ball positions inside the left heel and 8" behind that. Here are the results.

Forward ball position Rear ball position
Wrist angle
at impact
Wrist angle
at impact
281 g 89.1 mph -1.8 88.5 mph 0.7
290 g 88.4 mph -1.9 87.7 mph 0.5

The red numbers are the new, MOI-matched wedge played from inside the left heel.
The blue numbers are the old, swingweight-matched wedge played from 8" behind the left heel.

It is true that increasing the head weight costs a little clubhead speed. But, as it turns out, the clubhead gets that speed back if it has 8" more to accelerate before it strikes the ball. So clubhead speed is a wash.

But the wrist angle has cupped by about 2.5 in the forward position, compared with the rear position. That translates into about 70% of the loft difference between clubs. So it would account for most of a club's worth of lost distance.

What do I intend to do about it? Frankly, nothing. I could tweak the lofts to get back the distance. But I don't want to. Not many golfers are willing to accept this fact, but the only clubs where maximizing distance is important are the driver and the longest fairway club. For all other clubs, reliable, predictable distances with good spacing are much more important than more distance. I think the spacing for this set is good, so I'm going to learn to live with it.

For now, the MOI-matched set is in the bag. We'll see what happens when the honeymoon is over.

Last modified -- March 27, 2008