Hit down on your irons - the pros don't!

[ManinBlack]

Came across this fascinating bit of information the other day. The reason why a divot is taken with an iron is because, on impact, the club is deflected downwards due to the action / reaction effect, which is one of the laws of physics. The ball goes up, therefore the club must go down.

Look at the Swingvision clip of Justin Rose's iron shot here http://www.tutelman.com/golf/ballflight/downdeflect.php You can see that the club comes into the ball virtually parallel to the turf and only goes into the ground well after the ball. You can see the downward deflection of the club quite clearly. Approaching the ball this way gives a bigger margin for error and helps avoid the mistake of either digging in & hitting the shot fat or thinning the shot.

I find this quite fascinating. In fact thete is lots of interesting scientific stuff on this website, written by a golfing engineer.

 

[srixon 1]

I don't buy it. Any deflection would be miniscule to have this much of an effect. Surely the divot is just where the club reaches the bottom of its arc.

Does that mean that when the downward deflection takes place the shaft stretches downward too?

 

[Foxholer]

That deflection - which Newton's 3rd Law and Conservation of Momentum predict/require is miniscule in relation to the effect of a significant positive Attack Angle!

It certainly doesn't explain the monstrous steak sived divots that many take!

 

[Three]

Came across this fascinating bit of information the other day. The reason why a divot is taken with an iron is because, on impact, the club is deflected downwards due to the action / reaction effect, which is one of the laws of physics. The ball goes up, therefore the club must go down.

Look at the Swingvision clip of Justin Rose's iron shot here http://www.tutelman.com/golf/ballflight/downdeflect.php You can see that the club comes into the ball virtually parallel to the turf and only goes into the ground well after the ball. You can see the downward deflection of the club quite clearly. Approaching the ball this way gives a bigger margin for error and helps avoid the mistake of either digging in & hitting the shot fat or thinning the shot.

I find this quite fascinating. In fact thete is lots of interesting scientific stuff on this website, written by a golfing engineer.

I agree that there's deflection, but I disagree that the clubhead is not descending before it hits the ball.
It looks to me like it's descending, and when you look at the shaft lean it seems obvious that a divot would have been taken if no ball was there.

 

[ManinBlack]

I don't buy it. Any deflection would be miniscule to have this much of an effect. Surely the divot is just where the club reaches the bottom of its arc.

Does that mean that when the downward deflection takes place the shaft stretches downward too?

No! The whole club does, you can see a definite downward vertical movement. The swingpath may be slightly downwards but not anything like as much as I imagined it would be.

 

[ManinBlack]

That deflection - which Newton's 3rd Law and Conservation of Momentum predict/require is miniscule in relation to the effect of a significant positive Attack Angle!

It certainly doesn't explain the monstrous steak sived divots that many take!

Don't think it would be miniscule. There's not that much difference between the mass of the club that of the ball. Yes, the ball is lighter and therefore moves much more than the club but the high force of the impact definitely moves the club. A physicist could measure the actual amount.

 

[Foxholer]

Don't think it would be miniscule. There's not that much difference between the mass of the club that of the ball. Yes, the ball is lighter and therefore moves much more than the club but the high force of the impact definitely moves the club. A physicist could measure the actual amount.

Oh, I agree it moves- clearly visible in the vids.

The club-head is 5+ times the mass of the ball (and add the mass of the shaft too, which is more than twice the mass of the ball!).

That effect would explain the 'scrape' that happens in Tiger's strike but, as I posted earlier, not the massive divots many take! That is only explained by downward AoA!

 

[Canary_Yellow]

I'm not sure that video is the best example given that it's a long iron with the ball teed up. Surely there is more of a sweeping motion to that particular strike?

Isn't the extent of the divot linked to the position of the hands relative to the ball at impact? The further in front they are, the more shaft lean there is, the deeper the divot? So with a long iron, the clubhead and hands will be in a more similar position and there will be less of a divot.

I'm no scientist, but I don't believe that the divot is solely a result of the downward deflection.

EDIT: What I would add though, is that I don't think there should be a conscious feeling of hitting down on the ball. I think the downward angle of attack should be a product of a good swing from a good setup.

 

[duncan mackie]

Don't think it would be miniscule. There's not that much difference between the mass of the club that of the ball. Yes, the ball is lighter and therefore moves much more than the club but the high force of the impact definitely moves the club. A physicist could measure the actual amount.

You need to consider the momentum not just the mass...

But

1. I agree with Three 100%
2. You clearly had a mental image of a steep angle of attack in relation to the maxim of hitting down on the ball; this really isn't the case at all - especially the longer shafted clubs.

 

[the_coach]

all the best outcomes in results of normal full iron shots are struck with -AoA

so it follows all tour Pro’s must have a descending AoA with there irons - which they do

if folks then want the optimum strikes for optimum trajectory, accuracy & distance there has to be a -AoA

less downwards with the longer irons(metals) more so with the shorter - contributing factors also include shaft length & ball position & a forwards leaning shaft angle - but it’s a real small difference in degrees

at impact face deflection on a vertical axis happens as does deflection on a horizontal axis but it affect on either club head direction or ball travel is minimal - a ball & face are in contact for less than half a millisecond

the issue is with folks perception of what constitutes an optimum downwards AoA

AoA with a 6i is approximately -4º
most index players think of downwards as steep

just hitting down will not increase the optimum transfer of energy face to ball or in 'old money' teaching or commentator terms - ‘compression’

hitting more downwards per se will not increase the ‘compression’ of the ball will not increase the spin on the ball - just means the face angle & the clubhead direction both move down together - so there is no change in spin or increase in distance

there are 2 ways to ‘compress’ (optimum transfer of energy at collision) the ball better at strike

deloft the face angle more at impact without hitting down more
or hit down less without increasing the loft of the face at impact
as an optimum the answer would be to deloft the face angle without hitting down in degrees any more than is optimum
-from a wedge around -5º to a 3 metal at -2.9º so just over 2º of difference throughout a Tour Pro's bag

what is key to strike (centered location) is lower dynamic loft face angle along with a pretty ways shallow -AoA but delivered with a forwards leaning shaft approx 5º or 6º (within delivery there is generally a factor of around a couple of degrees of shaft flex bend also)

 

[sev112]

It's a perfectly viable theoretical and physical mechanism

Shame he forgets the friction component of the face of the club on the compressing ball in his free body diagram, and hence gets the consequential direction of the ball wrong accordingly

But other than that it all seems very viable

 

[One Planer]

Justin Rose' trackman data for an iron suggests other wise:

 

[sawtooth]

The golf teaching that I follow does not advocate hitting down on irons or any club for that matter. Instead I have the same swing thru the bag but the ball position changes.

With ball further back in your stance the iron will strike ball on a slightly descending blow but that's the swing and the club face doing that, I am not consciously hitting down. I am just swinging the club.

 

[ManinBlack]

AoA with a 6i is approximately -4º

And yet in the example shown in my original post the club is measured as coming in at an A of A of - 0.4°, & it looks like a 5 or 6 iron. In the Luke Donald clip too the A of A looks negligible. I still think that a relatively flat A of A means that the strike doesn't have to be as accurate as it would need to be if the club came in steeper.

All this really means to me is that advice to "hit down on the ball" is misguided.

 

[One Planer]

Justin Rose' trackman data for an iron suggests other wise:

Tour Trackman averages:

Note the driver AoA tour average

 

[Three]

.

All this really means to me is that advice to "hit down on the ball" is misguided.

Sorry, I disagree.

It's all relevant to what people are naturally doing. If you spent your days in front of average mid to high handicap golfers who scoop the ball, you would certainly hear yourself trying to get them to hit down on the ball.

 

[ManinBlack]

Tour Trackman averages:

Note the driver AoA tour average

There's a suggestion in the article referred to in the OP that the Trackman figures reflect the A of A after some of the deflection has taken place. The two slo more clips don't look anything like - 6°

 

[One Planer]

There's a suggestion in the article referred to in the OP that the Trackman figures reflect the A of A after some of the deflection has taken place. The two slo more clips don't look anything like - 6°

Here's a clip on YouTube of Tigers famous Stinger with a 2-iron.

[video=youtube_share;wL76OQ7ITmw]https://youtu.be/wL76OQ7ITmw[/video]

If you watch from 16 seconds in the swing through the hit is slowed down to to super slow mo (alleged 68000fps).

The path of the club down to, and through the ball, doesn't change.

The club continues a steady decent through the ball grazing the turf on the target side.

IMO that can only happen if the AoA is negative through strike.

 

[Bazz]

I always try to hit the ball on the up, sweeping it off the floor. Don't think I've ever taken much of a divot.

 

[ManinBlack]

Here's a clip on YouTube of Tigers famous Stinger with a 2-iron.

[vid

That's a very special kind of shot though, isn't it? And you can clearly see the club move downwards at impact by roughly the depth of the divot.