Finding optimum MOI

[bbbrisco]

I plan on heading to the range with some impact stickers and lead tape in the near future, and wonder if you have any advice on the process of finding an optimal MOI?

1) How much weight to add per trial? I'm guessing 2g might be a good balance between number of tests and finding a match, with perhaps a 1g final fine-tuning once nearest 2g weights have been found. I plan on pre-cutting my lead tape to lengths which weigh 2g (+1 1g piece) prior to heading out.

2) Any input on which iron to match? Theoretically, you should be able to do any of them, but I think I'll have less 4-iron swings in me than 8-irons, for instance. Or does the fact that a 4-iron wears me down quicker than an 8-iron indicate a problem with my swing? My initial thought is to do a 7-iron or 8-iron.

3) How many strikers per test weight to get a meaningful pattern? Would 5 balls be enough, or will I need to go more? More data is better, but I'm worried that hitting too many balls will cause my swing to change over the course of a test. I know I've had to break a fitting over 2 days before because of fatigue after hitting shots for 2-3 hours in a row.

[dcell]

I'm thinking of doing this too soon with my clubs. I think my plan of attack will be to see if any club in the PW - 7 iron range has a better impact pattern and then add the tape to the clubheads for clubs longer than my best and add tape to the grip for clubs shorter than my best. Does that make sense for the shorter clubs?

I think Tutleman concluded that a 1.3 swingweight slope (i.e. each club changes by about 1.3 in swingweight) is about right for MOI matching. 2 grams is probably a good starting point.

[Richie3Jack]

What I typically do is I get a customer a Wishon 6-iron model in their hand for them to demo. I'll install the shaft they want to the length and lie angle that they want.

The reason for this is because the Wishon iron heads are very light in weight. I don't think there¡¦s an OEM out there with lighter head weights. GolfSmith¡¦s Snake Eyes heads are super light as well but, Wishon used to the head of their club design.

Where you will see the MOI change the most is when weight is added to the head. That's because it's closer to the club's axis of rotation. So in this sense, it's very much like swingweight¡Kadd weight towards the head, MOI and swingweight increase.

So due to the lighter head weights in Wishon clubs, I can pretty much ensure that if I assemble a 6-iron together to the golfer's specs, it's very unlikely that the 'basic' club will be at too high of an MOI.

That¡¦s a good thing. If it's too high to start off with, then the golfer either needs to play with a different shaft, probably lighter or at least more butt heavy. Or they will have to grind the head to take some weight off (I don't grind heads).

Therein lies a potential problem with OEM clubs. Your 5 or 6 or 7 iron without any weight added to the head, *may* have an MOI that is already higher than your optimal MOI for your swing.

Let's say that I am omnipotent.

And let's say that I magically know that your optimal MOI is at 2,700 kg/cm^2. However, if your OEM clubs are higher than 2,700 kg/cm^2, you won't know your optimal MOI if they are too heavy.

The reason why I recommed the 5 or 6 or 7 iron is that something like a 3 or 4 iron *might* be too difficult to really get the impact dispersion small. And something like an 8-PW may be too easy (shorter club, easier to hit).

The way I do the MOI fitting is I take:

A big yard stick (4 feet long)
Impact Tape
Lead Tape

I'll add impact tape, hit 3-5 balls and check out the impact dispersion. I like the yardstick because I put it the impact tape that I just used, onto the yardstick. This allows me to compare the dispersion. Usually with irons, you¡¦ll see such a noticeable difference that it's not hard to decipher which is better.

Anyway,after that I had a strip of 1-gram high density lead tape to the back of the head. I'll add a new piece of impact tape, Hit 3-5 shots and check out the dispersion. I repeat the process, adding 1 gram of lead tape each time.

I have always found the same thing, in the fittings I've done. The impact dispersion varies as we add more weight and then it starts to improve quite a bit, then I add 1 more gram of lead tape and that is perfect for the golfer and the impact dispersion gets very tight. I then make note and I'll add another gram of lead tape, just to be sure. And without fail, each time the impact dispersion is all over the place. It's like there's a threshold for the weight the golfer can handle.

Now, when I help people with OEM clubs, I have to measure the MOI of each iron in their set. I find the lowest MOI in the entire set and tell then to try the process with that iron. The problem is if the lowest MOI is not a 5 or 6 or 7-iron, we can run into some issues.

Lastly, there is the "best club in the bag method." This is an old method where the golfer tells the clubfitter that a certain iron in their bag is the "best club in the bag." The clubfitter then measures the MOI and matches the rest of the set to that club.

I don¡¦t think it's bad per say. However, it's incomplete. For instance, my best clubs in my bag before I got into MOI matching were my 4-iron and 7-iron. Not by coincidence, they had idential MOI's of 2,700 kg/cm^2. In fact, they had the highest MOI's of my entire set. So at first, I matched the entire set to 2,700. Also, I knew I was onto something with MOI because my worst clubs in my bag were my 3-iron and 9-iron, which had the lowest MOI of any of my irons (2,625 and 2,645).

The problem is that while matching MOI like this was better than nothing, my optimal MOI was at 2,725. So I couldn't quite get the full effect of MOI matching.

I believe Tutelman has a mathematical formula to help determine the MOI of each club. It's not as accurate as the machine, but it gives a decent ball park. You could use that to find what club has the lowest MOI, then do MOI fitting from there.







3JACK

[Richie3Jack]

Here’s a brief MOI-matching example.

I recently purchased a Wishon 555M Gap Wedge. This is at 52° loft. The idea is to have something in between my SW and PW for full shots as I doubt I’ll use it around the green much.

Here’s the dimensions of the club, dry assembled with the grip on:

Length: 36-1/8” long
Static Weight: 441 grams
MOI: 2,580 kg/cm^2

Here’s a problem, the static weight and MOI are wayyy too light. My PW (which is 36-1/2” long) has a static weight of 451 grams and a MOI of 2,725 kg/cm^2.

Thus, I need to get the static weight for the Gap Wedge heavier than the PW in order to get the MOI to match.

I guess it has something to do with the length I cut the PW and GW to as when I originally did the PW, the MOI came out to 2,610 kg/cm^2. I then added a 9-gram hosel weight and some lead tape to get the MOI to match.

With the gap wedge, I added a 9-gram hosel weight. That will move the static weight to 450-451 grams (you have to account for the weight of the added epoxy, which should be less than a gram).

Thus, when I get home tonight and look at the wedge, I will have to add about 5-8 grams of lead tape to the back of the head to get the MOI to match 2,725.

According to Wishon, you don’t see a difference in face angle numbers on Trackman at impact until you have 12 grams or more of weight added to either the toe or the hosel. More than 12 grams starts to show a slight difference as if it’s added to the hosel, the heel of the club will slow down and cause the face to close more. 12+ grams on the toe means the toe slows down and the face opens.

Here I’m only adding 9-grams to the hosel and then adding 5-8 grams behind the club. I’ve had no problems with the PW where I added almost as much weight. So we’ll see how this works out as well.

I’m guessing in the end the specs will look like:

Length: 36-1/8”
Static Weight: 456-457 grams
MOI: 2,725 kg/cm^2






3JACK

[golfbaka]

1) I did my testing with 1 gram rare earth magnets but working in 2 gram increments and then fine tuning from there.

2) If you get tired swinging the 4 iron my guess would be that the MOI of the 4i is too high for you.

3) I would think 5 would be sufficient but you may want to run the test a couple of times to make sure the results weren't a fluke. I would hit about 5 balls to warm up after you've applied the lead tape, then apply the impact tape and do the test.

[Richie3Jack]

I use a 6-iron and base everything (shaft length, lie angle, etc) off the 6-iron. It's not too long in length that the impact dispersion can be difficult to decipher and it's not too short where it's too easy to make the impact dispersion small.





3JACK

[ericpaul2]

Have you seen anyone whose optimum MOI changed over time? I would think that major swing changes or even just gradual improvement (or deterioration) of fitness levels might make a difference. I'm guessing the former might be a sudden change, while the latter might take years to become an issue.

[Richie3Jack]

No, I only have about 8 months of experience with it. My optimum MOI I believe has changed a little. I'm about 5 kg/cm^2 more with the irons and driver and 10-15 more with the 3-wood.

When doing MOI matching, we are basically measuring the amount of force required to swing the club.

Force = Mass x Acceleration

So, if we alter our swing enough, like going from a full sweep release (ala David Toms) to more of a snap release (ala Boo Weekley), that would alter the acceleration profile of the downswing and would likely mean the player needs a higher MOI match for their swing.






3JACK

[Richie3Jack]

Great thread at GolfWRX (yes, it's possible) started by Tom Wishon (that's why it's possible) on MOI fitting and matching.

www.golfwrx.com/forums/topic/712584-what-is-swingweight-why-is-it-important-how-do-i-find-the-right-swingweight/







3JACK

[bbbrisco]

Thanks for the link. Tom's post was, as always, pure gold.

Another gem from Tom I recently stumbled upon was this
www.golfwrx.com/forums/topic/695732-does-the-ball-matter-test/page__st__30#entry5463354. I never knew about the swing speed turning ball flights from ballistic to aerodynamic, and this explains why many of the shorter hitters I play with seem to play about the same with any ball, whereas most longer hitters I know tend to put (lack of) spin off the tee high on list of desired ball characteristics.

I should probably go dig up and read all of Tom's posts on GolfWRX. I hate to think of what I might be missing.