Draw Spin Question

[mthunt]

I'm curious how these HMT numbers cause a draw with an 8 iron. Any idea?

Thanks

[DannyMRICS]

I'm curious how these HMT numbers cause a draw with an 8 iron. Any idea?

Beats me! Club data looks like it should be about 1.8* push with fade.

If it was hit off the toe, that could cause some draw spin because of gear effect, but not sure if it could make that much difference, and doesn’t account for the initial side angle ....

????....

[mthunt]

It was flushed. Here’s an HMT pic showing not toe. I took a few trying to get the best image.

[LEO MODE]

Can't see the impact but I have a feeling it's likely hit on the toe thus caused a draw.

Based on the numbers, the ball should be starting from the right and spin itself back to the middle or ever so slightly to the left of the target.
I think there are 2 speculations in my opinion:

1) Since GC2 and HMT output data separately, there is likely a discrepancy or fault in the numbers outputted in either or both devices.
2) I found out that GC2 likely has a slight draw bias than real life, and HMT has more deviations in Face Angle. Therefore, assuming that GC2 was right (as GC2 is the one that outputs ball data to present it in the software), then Face Angle was more closed than what HMT is showing.

If GC2 is wrong, then Spin Axis was a bit more positive.
If HMT is wrong, then Face to Path should be a negative number (likely Face Angle being more closed than what it's showing).

One other factor to note is that HMT always seem to show exaggerated dynamic loft. With an 8 iron it should be somewhere in the low 20's. So what that means is Face to Path and Spin Axis wouldn't cause that much of a hook/slice than say a driver.

I guess we can go on from there....

[mthunt]

The funny thing for me is that the draw bias only presents in my sim. When outside it doesn’t show draw. Strange. Plus, of my friends who are all strong players, only I show draw. I’m straight outside to even fade.

In this the ball started slightly right (almost straight) then draw like the GC2 numbers dictated. I just don’t understand how if the face is open to path.

Thanks for the thoughts.

[LEO MODE]

Yeah, if you think face to path is suspect then it could be either Face Angle or Club Path being slightly off.

As Stingreye mentions below, Lie could also play a role too. Check if it was an upright shot.

[mthunt]

I’ll check that tomorrow.

[LEO MODE]

Ok so it was a centered strike....HMT's impact location is very accurate so I would say then GC2's showing more negative Spin Axis...

[wbond]

So which is “more “ accurate the gc2 or the hmt? Or tighter tolerances

[mthunt]

They list the same tolerances but I test the GC2 vs real flight outside. It’s accurate

[Stingreye]

Mthunt, I would bet money it was lie angle. Toe likely was up. Switch the lcd display to show lie angle vs dynamic loft.

edit: I can try to find a few shots to show the impact of lie angle on my fsx live account. Whenever the “ball flight” laws seem to be violated, the lie angle and/or impact location have been the reason for me. Early on I thought my hmt was broken until an instructor that uses hmt showed me the the hmt was not lying.

[LEO MODE]

I agree, it could also be a lie factor too. There is some tolerances with the launch monitor too so since your shot should've been pretty much straight it can just be that slight 2-3 degree differences that made the difference. Perhaps you can also try some moderate to extreme hooks and slices and see the numbers and go on from there too.

[Stingreye]

Although not perfect, the face to target is likely around .8, (subtracting path from face to path). Ball went .3 right. I would have thought the face at .8 with an in to out path would have the ball starting further out to the right. HOWEVER, if that toe is up, that would be more likely to Start the ball further left similar to your .3. It also would also cause some draw spin. Lie angle will impact shorter clubs the most. I had a great wedge fitting recently and he spent the majority of the time dialing in my lie angles.

[LEO MODE]

Face Angle was 3.8 degrees open because Face to Path is Face Angle minus Club Path. So now that Mark said it was toe up, Face Angle should've been presented more closed to make sense (assuming lie angle was presented accurately). I am speculating somewhere around 1-2 degrees open (ballpark) as Spin Axis value was around 5 degrees to the left which would create that nice little baby draw. What was the Side distance Mark? That could tell me even better information on where the ball should've started in the first place.

[LEO MODE]

Also I'm sure you are already aware, but Launch Direction is about 75% of Face Angle and that Launch Direction number is closer to Face Angle than Club Path, it's also a likely chance that Face Angle should've been way more closed than current number (at 3.8 degrees open), as Launch Direction was only 0.3 degrees and Club Path was 2.3 degrees open. Launch Direction matched highly with Trackman outdoor too so assuming we have about 0.5 degrees of tolerance, it looks like Face Angle also should've been about 1 degree closed or open rather than 3.8 open reported as it is, which could then match both Launch Direction as well as Face to Path numbers more accurately.

I feel that it's probably due to HMT's inconsistent Face Angle parameter, as Club Path was more consistent than Face Angle in research studies and if you had a lower number on Face Angle, it would've created negative Face to Path which explains your issue clearly.

[LEO MODE]

You can also look at this for a reference, just look at Conclusion on the last page.

https://www.mdpi.com/2504-3900/2/6/249/pdf

[mthunt]

So the bottom line is that the HMT is likely not wrong.

[LEO MODE]

The other way around

[mthunt]

I hit some balls today. I’m average 2.6-3 degrees toe up on an 8 iron.

[andygg1986]

Yes, you need your lies bent 2 or 3 degrees flat, not more upright.

[LEO MODE]

Try bending it flat 2 degrees and go on from there. I would be cautious to keep bending it especially if the iron was cast. Because I’ve seen people bending it and ball flight was the same. But with your consistent swing I’m sure it’ll solve the issue.

[Golfbeat]

I stand corrected.

[StuartG]

Sounds like you tracked down the issue - but for future reference:

For those of you originally suspecting gear effect, it's rarely going to be a significant contributing factor an iron. Gear effect requires the head C.G. to be sufficiently behind the face impact location to effect the spin. Driver, woods, even hybrids - certainly. Irons, not really.

[LEO MODE]

I agree. Below link sums it up pretty nicely as you said.

https://blog.trackmangolf.com/hows-my-strike/

The author couldn’t answer my question on some numbers not being explained because I think Trackman also has error tolerances like HMT and is even more worse on tracking impact location which would present numbers we can’t explain. Ball physics should explain the numbers clearly as it’s not like our body with billions and billons of neurons working together.

[mthunt]

Does lie angle effect ball flight on a driver? I'd think it would.

[andygg1986]

It does but not nearly as much due to the lower loft. You can visualize it by laying the club on the ground with the toe pointed straight up. The face of a driver would be aimed around 8 degrees left, but a lob wedge would be closer to 45 degrees left. Of course that would be the extreme case of your club being too upright, but it makes it easier to see. In your case of being a few degrees upright, a driver would be negligible but short irons would see an effect

[StuartG]

Actually, the differences among different clubs (lofts) are not as big as you might think.

https://www.tutelman.com/golf/design/lie1.php

[DannyMRICS]

Very interesting thread. Made me look at my latest Trackman (outdoor - normalised) data more closely:

This data is an average over a few shots - similar to the OP, with the driver my face-to-path is open, but the spin axis is negative (right-to-left). In this case, because it’s a driver, does this mean I must be striking it off the toe (gear effect).

See also the attached photo of the impact position of a few drives on the course yesterday - the strike pattern is from low-heel to high-toe. Does this mean anything (or just that I need hit the centre of the face more!)?

I haven’t collected evidence, but I feel like I hit closer to the centre on all my other clubs (see strike of a single shot with my 3w from yesterday.

Thanks,

Dan

[mthunt]

Those clubs have some use. Oh boy. FT9?

[DannyMRICS]

Ha ha. Yes, over 10 years old. Callaway 460X Tour.

[DannyMRICS]

Actually, the differences among different clubs (lofts) are not as big as you might think.
https://www.tutelman.com/golf/design/lie1.php.

So, toe-up at impact with the driver and/or a toe strike could cause more draw spin than indicated by the face-to-path?

I wondered if that low-heel to high-toe strike pattern might indicate a toe-down: then the impact variance is mostly horizontal, with little vertical variance....

Dan

[StuartG]

So, toe-up at impact with the driver and/or a toe strike could cause more draw spin than indicated by the face-to-path?

I wondered if that low-heel to high-toe strike pattern might indicate a toe-down: then the impact variance is mostly horizontal, with little vertical variance....

Dan

Toe up could for any club. A toe strike could for driver/woods/hybrids but not really for irons.

Some people use impact patterns to judge lie angles - but I don't recommend it. There are too many other factors that could be contributing to the impact location. Best to check the lie angle directly and it's really easy to do. Just get a dry erase marker and put a straight line on the ball. When you position the ball on the mat or tee to hit, make sure that line is vertical and in a position to impact the face. This will leave a line on the face that will tell you whether the lie at impact is upright or flat or perfectly fine.