Launch Angle - Where am I going wrong?

This is the place for any questions and discussions about TrajectoWare.

Moderators: fschmidberger, dtutelman

Post Reply
Anthony
Trusted user
Posts: 19
Joined: Mon Jun 11, 2007 11:37 pm

Launch Angle - Where am I going wrong?

Post by Anthony » Mon Apr 28, 2008 8:22 pm

Just when I thought I had it all figured out, I am once again confused and I guess it's a matter of terminology-hopefully.

I was under the impression that there was one optimum lauch angle for any given ball speed (and spin rate but I'd like to ignore that for now). If a ball is traveling at lets say 130 mph and the perfect LA was 13 deg.. I believe that that LA is 13 deg whether you are using a 9 deg of loft with a +4 deg AOA or 17 degrees of loft with a -4 degree AOA. Apparenty that is not correct.

If Dave or anyone can shed some light it would be appreciated.

Anthony

dtutelman
Site Admin
Posts: 107
Joined: Mon Apr 09, 2007 8:55 pm
Location: New Jersey, USA
Contact:

Re: Launch Angle - Where am I going wrong?

Post by dtutelman » Mon Apr 28, 2008 10:11 pm

Anthony,
You always ask interesting questions...
Anthony wrote:Just when I thought I had it all figured out, I am once again confused and I guess it's a matter of terminology-hopefully.
Not just terminology. It's something pretty basic, but a little subtle.
I was under the impression that there was one optimum lauch angle for any given ball speed (and spin rate but I'd like to ignore that for now).
Spin matters, but it isn't a big deal. But... loft angle (which is what creates spin), significantly affects the ratio of ball speed to clubhead speed.
If a ball is traveling at lets say 130 mph and the perfect LA was 13 deg.. I believe that that LA is 13 deg whether you are using a 9 deg of loft with a +4 deg AOA or 17 degrees of loft with a -4 degree AOA. Apparenty that is not correct.
OK, let's use your numbers of 130mph and the two ways to get the launch angle. I'm using TrajectoWare Drive for this; you can follow along on your own copy.

130mph ball speed, 9deg loft, 4deg AoA - This gives a launch angle of 12.1deg, not 13, but let's go with that. The carry is 194.7yd. Also important: the clubhead speed to achieve this is 88.5mph, and the spin is 2200rpm.

17deg loft, -4deg AoA, no change of clubhead speed - This is probably what prompted the post; the carry dropped to 186.6yd, a significant difference of about 8mph! But look at two things you have affected: the spin and, more important, the ball speed. The spin is now 4100rpm; that's a huge difference. Even more important, the increased loft causes the more glancing blow to impart less ball speed. The ball speed is no longer 130mph, it is down to 126mph. That loss of clubhead speed alone could explain close to an 8yd difference in carry.

17deg loft, -4deg AoA, change the clubhead speed to get a ball speed of 130mph - We have to crank up the clubhead speed to 91.4mph -- that's an additional 3mph -- to make up for the loss caused by all that extra loft. When we do that, we get back almost all our lost distance. The carry is now 194.3yd, less than half a yard off the low-loft, high-AoA combination. BTW, the launch angle is down to 10.3deg and the spin up to 4300rpm.

OK, so suppose we stick to launch parameters. Let's try a ball speed of 130mph and a launch angle of 13deg. We'll plot it for the two spins resulting from lofts of 9deg and 17deg. (Let's just allow the clubhead speed and AoA to be whatever; we're doing all our adjustment on the launch side.)

For 2200rpm, the carry distance is 198.1yd
For 4300rpm, the carry distance is 196.2yd

We see there is a little loss of carry distance from that huge difference in spin. There will also be a significant loss of total distance. Just look at the angle of descent and the final spin to confirm what the bounce and roll will do.

So... Two things to remember:
  • If you change an impact parameter, you will change launch parameters -- sometimes in ways that surprise you (until you get familiar with them). Similarly, changing launch parameters changes impact parameters in complex ways.
  • The trajectory with the lower loft and higher AoA may have the same carry, but it will result in a longer total distance.
Hope this addresses your issue,
DaveT

Anthony
Trusted user
Posts: 19
Joined: Mon Jun 11, 2007 11:37 pm

Post by Anthony » Tue Apr 29, 2008 8:36 am

Dave,

As always, thanks for the info. I certainly understand that for a given clubhead speed that the ball will have less speed with an increase in loft due to a more glancing blow as well as some additional spin. I'm down with that :-)

But here's part of the article I came across online and what got me thinking.
As you can see from the additional information, Bubba Watson swings the driver with a 5° Upward Angle of Attack, while Charles Howell III swings the driver with a -5° Downward Angle of Attack.

Each golfer’s Angle of Attack is purely a product of their swing characteristics. Quite simply, some golfers simply develop different Angles of Attack into the ball as a result of various individual swing habits and characteristics. Now let’s add one more column to the chart.

Player Ball Speed Launch Angle Spin Rate AOA Driver Loft
Bubba Watson 186mph 13.5° 2200rpm +5° 7.5°
Charles Howell III 172mph 7.0° 2800rpm -5° 11.5°

Keep in mind that both players are fully optimised for their driver performance as a result of having gone through extensive testing with the golf companies with whom each has an equipment endorsement contract.
At first glance I would think that Bubba needed to launch at a lower LA than Charles III based strictly on his ball speed of 186 versus 172. They say he needs a 13.5 degree LA while Charles III needs a 7 degree LA. I tried to plug in those numbers and cannot even get Bubba's to match up. For Charles Howell III I get a spin rate over 4500.

I just can't see CHIII launching at 5 degrees LESS than Bubba with a ball speed 14 mph slower and that's what get's me confused. I would just think that even with a negative AOA and using more loft and generating more spin that CHIII would need a higher LA than Bubba's.

The article that I am referring to is at:
http://www.iseekgolf.com/news/7313-angl ... in-fitting

Anthony

dtutelman
Site Admin
Posts: 107
Joined: Mon Apr 09, 2007 8:55 pm
Location: New Jersey, USA
Contact:

Post by dtutelman » Tue Apr 29, 2008 2:41 pm

Anthony wrote:The article that I am referring to is at:
http://www.iseekgolf.com/news/7313-angl ... in-fitting
Rather than dealing with your impressions, let me comment on what the article says.

I brought up TrajectoWare Drive and ran the numbers from the article. Turns out I had four rows in my table, not just two like the article. That's because the article gave both impact parameters (driver loft, AoA) and launch parameters (ball speed, launch angle, spin) -- and they did not agree according to the program. (More about the discrepancy below.) Here's my table.

Image

The yellow rows are based on the article's launch parameters, the green rows on the impact parameters (keeping the ball speed from the article, because clubhead speed is not given).

What do I get from examining this?
  1. When I go to the impact parameters, I get a higher spin and a lower launch angle than the article cites. That's true for Watson (400rpm difference) and Howell (almost 1000rpm difference). The Watson difference can be explained without too much difficulty by citing vertical gear effect. I'm much more cautious about explaining Howell's difference; 1000rpm is a lot for gear effect to remove.
  2. The difference in carry due to this difference in spin/launch is only about 3 yards for each golfer. That's worth optimizing for, but not worth buying a new driver if it isn't how you make a living. BTW, the carry distance for the yellow rows is within a yard or two of what the article reported.
  3. Wishon states that each of these golfers is using the optimum driver for his swing. I decided to test that. For the yellow rows, I varied just the spin, and found that the driver was indeed optimal. (In order to vary launch angle without varying spin, I would have to assume a different attack angle, and that is outside the ground rules -- the AoA is a property of the golfer's swing.) For the green rows, I varied just the loft; again, the driver is indeed optimal.
I didn't go checking the big table of optimum drivers at the bottom of the article. But, if you choose to study it, be forewarned that there is a serious terminology difference between Wishon and me: "Dynamic Loft". Wishon includes the effect of AoA in his dynamic loft; his is mine PLUS the AoA. I think that is misleading for a variety of reasons, which I am willing to discuss if anyone is interested.

Bonus feature:
Some interesting uses of TrajectoWare Drive


I ran into a few interesting things while using the program to research this thread:
  • The table above was created using the Table View of TrajectoWare Drive. I exported it to Excel, where I added the labels and colors for the rows. (Instructions for doing this are in "Help".) Then I took an image snapshot of the Excel window, copied this to IrfanView (a good freeware picture editor), cropped it to the rows I wanted, and included it as an image in my post.
  • You may notice that, in my post yesterday in this thread, the carry distances were somewhat longer than you probably got. That was because I still had it set up for elevated tees from a recent use. I had played a course that I play a lot, and wanted to check an experience there. The white tees that I hit from were moved to the back teeing area, which is about 20 yards back and 10 feet higher. I hit a really good drive, that went farther down the fairway than I am used to, even from the normal white tees. So I decided to see whether the extra distance (including the back tees) could be explained by the extra 10 feet of elevation. Turns out the elevation was not enough to cover the extra distance of the drive; I did hit it really well.
Cheers!
DaveT

Anthony
Trusted user
Posts: 19
Joined: Mon Jun 11, 2007 11:37 pm

Post by Anthony » Wed Apr 30, 2008 12:34 am

Well Dave, I really don't know where to start.

Let's see. You have 2 sets of numbers. I do not see anything regarding impact parameters versus launch parameters. I enter the numbers they quoted: a ball speed of 172, an angle of attack of -5, and a launch angle of 7 and end up with a Dyn Loft of 13.9, a spin rate of 4574, and a carry of 264 yards with a AOD of 47.4. This is in no way optimized in my opinion. You have an AOA of -0.7 in your chart. This is where I must be going wrong. I figure there could only be one AOA and that's -5 deg (a descending swing to the ball).

Also, other than a correction for spin, I believe that 2 balls leaving the clubface at the same exact speed - one from a club at 10 degree loft with a 0 degree AOA and the other from a 13 degree loft at -3 AOA will need the same launch angle. In the Bubba / Charles example, Charles swings 14 mph slower and instead of launching at a higher angle than Bubba he's launching 5 degrees lower! I just don't get it. I have yet to see a launch angle chart that shows lower launch angles for slower swing speeds.
I only rant to show my thought process and frustration. Anyway, don't give up. I'm sure that I must just be missing something.

One final thing, if you had to pick a AOD for an optimum for carry and roll, would you say that a 35-40 degree range is pretty good? Just wondering what your take is on this.

Later,
Anthony

dtutelman
Site Admin
Posts: 107
Joined: Mon Apr 09, 2007 8:55 pm
Location: New Jersey, USA
Contact:

Post by dtutelman » Wed Apr 30, 2008 1:45 am

Anthony wrote:Well Dave, I really don't know where to start.

Let's see. You have 2 sets of numbers. I do not see anything regarding impact parameters versus launch parameters. I enter the numbers they quoted: a ball speed of 172, an angle of attack of -5, and a launch angle of 7 and end up with a Dyn Loft of 13.9, a spin rate of 4574, and a carry of 264 yards with a AOD of 47.4. This is in no way optimized in my opinion. You have an AOA of -0.7 in your chart. This is where I must be going wrong. I figure there could only be one AOA and that's -5 deg (a descending swing to the ball).
OK, let's start with the data in the article. You're talking about the Howell data, so let's look at that. The article gives the following info:
  • Ball speed = 172mph (a launch parameter).
  • Launch angle = 7* (a launch parameter).
  • Spin = 2800rpm (a launch parameter).
  • Angle of attack = -5* (an impact parameter).
  • Loft = 11.5* (an impact parameter).
All this is given. The problem is, it is not consistent!

In order to get this combination of launch and impact parameters, you must do some magic. If the "magic" is vertical gear effect, you'd need an awful lot of it. Anyway, TrajectoWare Drive does not incorporate vertical gear effect. And it probably never will, because it depends both on details of the clubhead and properties of the swing (how high on the face you hit the ball).

In other words, you can't use TrajectoWare Drive to tell you everything about Charles Howell III's driver. I did the next best thing; I studied it two different ways, first launch parameters alone and then impact parameters alone.
  • For the launch parameters, I used the launch parameters as given -- ball speed=172, launch angle=7, spin=2800. When you do this, the loft and AoA come out completely differently from the given data.
    In order to check optimality, I varied the spin alone; 2800rpm is indeed the best spin for that ball speed and launch angle.
  • For the impact parameters, I used the two impact parameters given -- AoA=-5, loft=11.5. Then I adjusted the clubhead speed until I got a ball speed of 172. When you do this, the launch angle and spin come out completely differently from the given data.
    In order to check optimality, I varied the loft alone; 11.5deg is indeed the best loft for that clubhead speed and AoA.
OK, does that make sense now?
Also, other than a correction for spin, I believe that 2 balls leaving the clubface at the same exact speed - one from a club at 10 degree loft with a 0 degree AOA and the other from a 13 degree loft at -3 AOA will need the same launch angle.
Simply not true! AoA converts directly into launch angle, degree for degree. Loft does not. For the way loft converts to launch angle, see my Club Design Notes at http://www.tutelman.com/golf/design/swing2.php#launch
In the Bubba / Charles example, Charles swings 14 mph slower and instead of launching at a higher angle than Bubba he's launching 5 degrees lower! I just don't get it. I have yet to see a launch angle chart that shows lower launch angles for slower swing speeds.
Sure you have! At least you have if you looked at the chart at the end of Wishon's article -- the one that kicked off this discussion. Compare the negative-AoA row at any speed with the positive-AoA row at the next higher speed. You'll see it every time.

The reason is that the spin makes a lot of difference. Spin keeps a ball in the air. If you have more spin, you need less trajectory to keep the ball in the air; in fact, too much spin on a higher trajectory will cause ballooning and hurt distance. So a negative angle of attack requires a higher loft, which gives more spin, which consequently requires a lower launch angle for optimum distance.
I only rant to show my thought process and frustration. Anyway, don't give up. I'm sure that I must just be missing something.
Yup! You were missing the effect of spin, and the fact that making up for a negative AoA will also give more spin.
One final thing, if you had to pick a AOD for an optimum for carry and roll, would you say that a 35-40 degree range is pretty good? Just wondering what your take is on this.
I have heard a rule of thumb that says, "Keep the AoD below 40 degrees." That's not a bad match to your suggested range.

My own personal approach using TrajectoWare Drive is to find the optimum carry distance, then back off (reduce) the loft enough to reduce the carry by about a yard. Look at the difference in AoD and final spin that comes from backing off. You have to believe that giving up that yard of carry will give you back a lot more in total distance.

Cheers!
DaveT

Anthony
Trusted user
Posts: 19
Joined: Mon Jun 11, 2007 11:37 pm

Post by Anthony » Wed Apr 30, 2008 10:40 am

Well Dave, the light has started to shine, albeit slowly. I apprciate your taking the time to reply to these posts.

I would say 99% seems to be clear. The one thing still remains a bit grey is how the AOA goes from -5 deg for his swing to -0.7 at impact. If you could touch on this that would be great.

As far as AOD is concerned, oddly enough I was doing pretty much the same as you. I would generate a small list and then take the smallest AOD from the ball speeds that were 1 mph less than the max distance ball speeds.

And finally, as a side hijack, do you have an opinion on the shaft contribution to dynamic launch? Or should I say would you like to express one. I believe that for most folks, even without a late release, the shaft pretty much will be lined up with the clubhead CG. Even a slight waggle seems to do this. The reason I ask is that to determine a clubhead loft from the dynamic loft leaves a lot of "guesswork". And then you need to factor in the clubhead design and it gets even a bit more difficult.

I would say the driver fitting process is getting easier and would almost be impossible without Trajectoware. It's really not bad if you can get someone down to a consistent swingspeed and AOD. What gets complicated is putting them on a launch monitor with their current club, deciding on what the new combination will be, and then hoping that it doesn't create a new set of launch conditions. A lot of times the new club will have a longer/shorter shaft, a lighter, heavier shaft, and more/less flex. Add that to a new head weight and loft and you have a lot of decision making.

Oh, and finally again :-), I just discovered what a difference in distance the gram weight of the head makes. I would have assumed it to be inconsequential. Far from it. Most of my drivers are in the 44-45 inch range and usually end up over 200 grams to get to D3 or so. What a nice bonus.

LAter,
Anthony

dtutelman
Site Admin
Posts: 107
Joined: Mon Apr 09, 2007 8:55 pm
Location: New Jersey, USA
Contact:

Post by dtutelman » Wed Apr 30, 2008 11:14 am

Anthony wrote:I would say 99% seems to be clear. The one thing still remains a bit grey is how the AOA goes from -5 deg for his swing to -0.7 at impact. If you could touch on this that would be great.
It's an artifact of the inconsistency between his launch conditions and impact conditions. Try this and you'll see what I mean:
  1. Fire up TrajectoWare Drive, and start a new trajectory.
  2. Set up the impact conditions: head speed=118, AoA=-5, loft=11.5. That is the imapact set for Howell, BUT... The launch conditions are all wrong except for the ball speed.
  3. Move to the launch condition side, and adjust the launch angle to get it up to the 7deg that Howell experiences. You have to crank up the launch angle about 2deg. If you just change LA without changing ball speed or spin, the AoA will change to adjust the launch angle. The AoA has now increased from -5 to -3.
  4. But the spin is still wrong. Adjust the spin down to 2800. That changes all three impact conditions. You need to reduce the loft in order to reduce the spin; you knew that, right? But, in order to keep the launch angle, you have to increase the AoA while you reduce the loft. The AoA has increased again, from -3 to -0.7. Finally, because of the reduced loft, you don't need as much clubhead speed to get the ball speed of 172.
I know it's a little mind-bending, but TrajectoWare Drive is the only program around that will compute backwards from launch conditions to deduce the impact conditions. (Other programs -- Dupilka's and Wishon's -- will compute forward from impact to launch, but not backward.)
And finally, as a side hijack, do you have an opinion on the shaft contribution to dynamic launch? Or should I say would you like to express one.
I have opinions but no measurements. I do have a project waiting to be done that will generate some numbers. Until then, I'm reluctant to say very much. Wishon's book has his fairly detailed opinion, but it sounds like you have read it. Until I have my own data, I consider that the best information around. (Even though my unsubstantiated opinion is slightly different.)
Oh, and finally again :-), I just discovered what a difference in distance the gram weight of the head makes. I would have assumed it to be inconsequential. Far from it. Most of my drivers are in the 44-45 inch range and usually end up over 200 grams to get to D3 or so. What a nice bonus.
You betcha! My own favorite drivers over the past couple of years are 44" or even less, with clubhead weights at or above 210g. But that's another thread altogether.

Cheers!
DaveT

Anthony
Trusted user
Posts: 19
Joined: Mon Jun 11, 2007 11:37 pm

Post by Anthony » Wed Apr 30, 2008 3:56 pm

Well Dave,

I think we have everything just about figured out. I believe it all started with the bad data (you refer to as inconsistencies) and that led me to some other revelations/issues. I believe I'm on top of it now.

Anyhow, "you gotta love it". Personally, I have so much equipment and golf stuff rolling around in my head there is barely room for anything else. I have to cut back.

Take care and I'm sure I'll be back in touch shortly,
Anthony

Post Reply