Optimal distance and Negative AOA with driver

Why does a negative angle of attack limit your max distance on a drive? Or is it just really hard to get optimal numbers with a negative aoa?

If I have a negative 4° AOA and use a loft/shaft combo that gets me to optimal launch and spin numbers, wouldn’t that get me max distance?

It’s going to be tough to get to “optimal” with a -4 degree angle of attack. It certainly can help you get better numbers, but that is a steep attack angle. Optimal numbers typically means getting launch angle up while keeping backspin numbers lower, giving you good carry distance and good roll out. Driver head CG, loft, impact location, play the biggest role. A shaft is very important as well, and if it’s not a good fit for you, timing and impact will certainly be negatively affected.

It's going to be tough to get max for your swing speed with a negative AoA because of efficiency and spin-loft. You increase efficiency (smash factor) when the face is squarer to the angle of attack (less of a glancing blow). Hitting level or up will always be less of a glancing blow than a negative AoA (in other words, as spin-loft increases the max smash factor decreases which is why you see smash of ~1.5 for driver and ~1.3 for short irons/wedges). This in and of itself isn't going to make a huge difference, but at -4º vs. +2º or so you may see a loss of a couple mph of max ball speed depending on delivered loft. The other factor is that with a negative AoA it's tougher to achieve that high-launch, low-spin shot that is optimal for distance. Because your AoA is negative, you're increasing spin-loft. To get spin down you'd likely need to reduce loft which then is going to reduce launch. You will likely find that you can get high launch OR low spin, but it's tough to get both (there are some modern drivers that have enhanced the ability to separate spin profile from loft like the SLDR though those tend to be far less forgiving drivers). So that in a nutshell is why it's nearly impossible to maximize distance for a given speed with a negative AoA.

Angle of attack or loft is 1:1 and part of Dynamic loft, and Dynamic loft x 0.84 = launch angle, so you need more loft than others to get to the same launch angle, (but only if thats the target), but the model who say smash factor drops and spin goes up is not possible to detect, or for short, i never saw any problems to get a PTR of 1.5 on Trackman no matter AOA, so its part of a mathematical model we dont see present real life. Spin levels on the driver is not ruled by spin loft real life, but vertical gear effects, so a player with negative AOA has the same needs as anyone else to make impact on the face where its beneficial.

But to get out to the absolute max for carry, we need a positive AOA, but if you look at Trackmans optimum charts, you DONT get the right picture since they have taken down ball PTR value to 1.44 for minus 5* but you can get 1.5 like all others, so they have removed 6 mph ball speed, and the spin level they use is not normal or what a negative AOA player will have either.

So we are back at the fact that Launch is 0.84 of Dynamic loft and AOA or Static loft both count 1:1 as part of Dynamic loft, a player with minus 4* compared with the same player at plus 2* (6 difference) will see a launch angle difference of 6 * 0.84 = 5.04* as difference on launch angle, but both ball speed and spin should be the same with the same impact.

A player with 100 mph club speed and a launch of 12* with 2500 rpms will get 239.5 yards carry and potentially 265 as total (lets say this come with negative AOA of 4*)

The same player with a positive AOA of 2* will with the same impact get 5* higher launch or 17* - still with 2500 rpms, and that gives 244,8 yards carry (5 yards longer) with a potential total of 265 (same total) so you loose 5 yards carry if you have a ball speed of 150 but nothing on total.

so the real difference is launch angle where 1* on AOA becomes 0.84* as launch.

Here is a small chart for conversion from a change of AOA or Loft and the response as Launch angle difference.

This is whats important if we want to have launch and spin levels under control, and thats impact height on the face. make sure its never below the center line.

The numbers is relative and like the head was fixed and the ball shot against the face with a air cannon, then we would see return values like this, all deepening on the height on the face we make impact. It better not be too high where the face COR value no longer is at the max, but most players who claims to have a spin issue has a impact height issue who can be solved very easy, raise impact location on the face.

Just look around on this charts, the first for 150 ball speed like the player have 100 club speed and 1.5 as PTR value, the next 165 mph ball speed or 110 club speed with 1.5 as PTR. Pick a "low launch" and a certain spin value of choice, now move 5 on launch angle with the same spin value....The difference to Carry and Total is what you loose or gain.

If we take it to the Extreme and say -5* AOA vs +5* AOA we have 10 dynamic loft *0.84 = 8.4* difference to launch so we can say we start at only 8* as launch for the player with -5* on AOA. Lets say we optimized him for that LA and that means 3000 rpm of spin who gives 228 carry and 256 as potential total.

With 16* as launch with 3000 rpm of spin we get 240 carry and 257 total (only 1 yard longer total) , so there is 12 yards carry from minus 5* to plus 5* unless we can improve spin value, so impact location and vertical gear effects is the problem if spin is as high as 3000.. Improved impact position on the face for the same player can add 1-2 on launch (9* to 10* LA), and spin levels can by ease be cut off 700 to 1000, so if we say 2* and 1000 as change or 11* 2000* we get 232 carry and 270 as potential total (14 yards more on total, and thats 13 yards more than the player with plus 5* AoA - 16* launch and 3000 rpm spin)

He will need more loft if he wants to improve his LA, and we should try that, and at the same time keep spin levels under control by taking advantage of vertical gear effects and a impact on the upper 1/3 of the face.

Adding the same chart for 135 mph ball speed or equal to a player with 90 mph club speed and a PTR value of 1.5 (Power transfer ratio or Smash factor)

And at last a "half chart" for 120 mph ball speed or 80 mph club speed and 1.5 smash. This is the player that looses the most if he has a negative AOA since launch angle is more important for him than it is for higher ball speed. Thats why the general advice for slow swingers is MORE LOFT and higher spin rates from higher loft dont hurt this players much either.

The 100 mph club speed player lost 12 yards carry from minus 5* as AOA to plus 5*, but this player with only 120 ball speed looses 14 at max spin value, and 20 yards on ideal spin values. But, if fairway conditions allows good roll out. spin values becomes more important than launch angle. It dont take much launch to get 200 yards total if spin levels is under control (high face impact), and that always improves launch angle vs center.

Thats correct, but we dont know why AOA became like it did, so this numbers are all "robot" scenarios, and we dont have control over neither actual loft on all head models due to roll, neither head twisting and addition to both dynamic loft and launch angle due to impact vs VCOG, a parameter who also involves shaft properties, its all just theoretical numbers who mostly explain what we can expect, but like with anything that has do to with Golf tech and fitting, what we expect to get from a certain change is far from always what we get.

Those numbers ive seen as a variable to the average 0.84 as a ratio between Dynamic loft and launch on DRIVERS is down to 0.70 and up to about 0.96, but for most (volume), the factor is 0.839, so im using 0.84 as factor when i make examples, and i have not noticed AOA as influence on that parameter, but ball speed or club speed seems to be of importance for that variable, LOW club speed against 0.70, HIGH club speed, against 0.100 (from 0.84)

PGA Average Dynamic Loft = 12.8 with a launch of 12.3 gives a ratio of 0.96, while LPGA has 15.5* Dynamic loft and 12.3* as launch who gives a ratio of 0.96

PGA has a negative AOA of -1.3* and LPGA a positive AOA of 3, or a difference of 4.3*

We also both knows that both Flightscope and Trackman have adjusted their Algorithms, so all charts is "the latest theory" from Flightscope using HARD surface as fairway, Sea level and 0 tilt on the spin axis.

Here is how it looked like on the old version of Flightscopes Optimizer for the 100 Mph player and minus 5 as AOA, all RETURN values from Flightscope, Some input values from Trackmans Optimum charts to get a DIFFERENCE for changes or improvements. (apple to apple on Ball speed, launch and spin.)