Just an update on some of this –
Some time last summer I built a set of Wishon irons for a friend of mine. He had some Mizunos and wanted to get MOI matched and fitted. I fitted him with his original Mizuno’s. When I fitted him for MOI I found that he had the same MOI as I have in my irons (2,725 kg/cm^2). He wanted to try a lighter shaft in hopes of gaining some distance. He was using a 133 gram Apollo shaft. We figured that as long as the shaft bend profile and MOI’s matched, we wouldn’t have a problem switching to a lighter shaft. The heft would be the same. I also MOI matched his Mizuno’s for free.
When he got the clubs built for him, he said he felt he was hitting the new irons better than his old non-MOI matched Mizuno’s. But, it was not as good as how well he hit the Mizuno’s when I finally MOI matched them. I then got it out of him that he went back to his old Mizuno’s and was very happy with how he was hitting them after they were MOI matched.
I asked him for both sets of clubs back. I re-measured them and everything came out like they should have. I then tried to hit both sets. I knew that his specs were a bit different from mine, but I should be able to hit them well. Well, I could hit the Wishon’s with the lighter shafts quite well. Didn’t hit the Mizuno’s with the heavier shafts all that great. I would have a tight impact dispersion, but I was more apt to miss low or high on the face (rather than towards the heel or the toe). They just felt overly heavy for me. When you measure the 5-iron swingweight to my MOI matched clubs, it comes out to D-5, so it’s not like I’m a total lightweight.
After that, I got some Edel wedges and noticed that their heads and shafts were too heavy for me. The MOI was the same. I then altered the shafts and had great success with the Lob Wedge. The Sand Wedge I think needs some weight taken off it.
Those experiences taught me that MOI matching is very effective, but to get the best ‘fit’ for clubs, you need to understand the weight of the main components (head, grip, shaft) and be able to determine the right combination based on the swing as well. My friend really cranks it on startdown and un-cocks his wrists much earlier in the downswing than I do with a more ‘float load-ish’ startdown and a late uncocking of the wrists.
I thought I was really onto something until I read on the Wishon site about a month ago with regards to what is called ‘MOI Balance Index.’ MOI Balance Index (MBI) is part getting the right combination of weight in the components and part the feel of the balance of the club. A clubmaker named Monte Doherty created a spreadsheet that is quite extensive and it calculates the Balance Index based on a variety of formulas and measurements.
After doing a lot of reading and examining Doherty’s spreadsheet, I saw that a large problem that causes the Balance Index to get out of whack is the shafts. Typically after the shaft is trimmed, it either gets a little lighter or virtually the same weight. The problem is when looking at the MOI Balance Index, the shorter clubs could use a heavier shaft and the lighter clubs a lighter shaft.
In fact, AeroTech has created a model of shafts called the ‘Player Spec’ which start off with a 96 gram 3-iron shaft and they get heavier in 2-gram increments.
This made a lot of sense to me as I have experienced (and others on this forum) that when a golfer utilizes swingweight matching, the longer irons feel too heavy and the shorter irons feel too light.
This is much better corrected when the golfer goes to MOI matching (progressive swingweight). However, there have been some complaints from golfers who got MOI matched that the long irons feel a tad ‘head light’ and the shorter irons feel a tad ‘head heavy.’
Looking at Doherty’s spreadsheet, he shows an example of his own clubs that he built. He needs to lower the Balance Index on his 9-iron and PW. This means that those clubs are too ‘head heavy.’ But, the way to properly reduce the ‘head heavy’ feel is to get a heavier shaft installed so the relationship between shaft and head weight alters to make the head feel lighter.
That’s what the ‘progressive shaft weight’ concept kicks in. The shafts get lighter in the longer irons to make the heads feel a little heavier while not making the overall club too heavy. Conversely, the heavier shafted short irons make the heads feel lighter without making the overall club too light.
The problem now is that only 1 company (that I know of) makes shafts that are in ascending weight. And AeroTech does not sell inexpensive shafts.
However, there was one clubmaker that gave a good suggestion for getting the MOI Balance Index to match when you need a heavier shaft.
Add lead tape to the shaft of the club.
I recently tried this as I assembled a Wishon 575MMC 7-iron together.
First and foremost, you still have to match the MOI. When I did this, I found that I needed about 2.8 grams more added to the shaft in order to get the MOI Balance Index where it needed to be.
I added it to the shaft and by inputting the new data in Doherty’s spreadsheet, the MOI Balance Index was in the range it needed to be (38-42). I tried the club out yesterday for the first time and it felt and performed great. Great trajectory and I don’t think the ball had more than a 2-yard fade or draw the entire practice session on the range.
Lastly, I also found that if you put the lead tape on the balance point of the club (on the shaft) it will alter the MOI. I actually had to put this lead tape up higher on the shaft up by the shaft label. It did not affect the balance point and it properly added weight to the shaft and drove the MBI to within the range I wanted it.
So far, so good. Up next I will be trying out this concept with my 3-iron and PW. But I think since I know that adding lead tape to the balance point of the club alters the MOI, I have a little more flexibility as to how much weight I want to add to the head and the shaft on the next club I try to execute this process on.
3JACK