Tuning Long Range Drivers for Desired Flight Characteristics
Alan Adler - Aerobie, Palo Alto, CA

Most disc golf players have noticed that their long range drivers change in flight characteristics as they become beat up over time. But of the many players I've worked with while developing discs, none were aware that they could deliberately tune their drivers to suit their throwing style and speed. No tools are required other than your own two hands.

I first learned how to tune flying objects while developing my Aerobie flying ring (which held a Guinness World Record for a throw of 1,333 feet), so it was natural for me to apply tuning to discs when developing the new Epic long range driver.

Before we get into the details of how to tune a disc, let's establish some terms. The discussion below applies to a backhanded throw with your right arm. Reverse any references to right or left if you throw either left-handed backhands or right-handed forehand throws.

Stability

Stability in the disc golf world has come to mean a disc's resistance to rolling right in flight.

An understable disc begins to roll right early in the flight. Understable discs must be launched with some downward lean (Hyzer angle) to counter their right roll.

An overstable disc is so resistant to right roll that it begins rolling left early in the flight. However all drivers tend to fade (roll left) near the end of the flight. Fade has been attributed to loss of spin during the flight. However it is actually caused by loss of forward velocity near the end of the flight. The more stable the disc, the more severe its end-of-flight fade. This can be countered by launching the disc with upward lean (often called AnHyzer).

Wind and Velocity Effects

Long range drivers are velocity sensitive. The greater the airspeed, the greater their tendency to roll right. Thus when you throw into a headwind it's necessary to launch with more Hyzer angle. Conversely, when throwing downwind you will need to launch with less Hyzer or even some AnHyzer angle. You can also tune your discs for different wind conditions.

Tuning

Tuning discs, by bending them, works on long range drivers. I do not recommend it for shorter range discs. A typical long range driver has a rim about 3/4" wide, which is about the width of a penny. Our new Epic driver has a variable-width rim which varies in width from one inch to 1.6 inches (fig 3 below). The wider the disc's rim, the more it responds to tuning.

To decrease the stability of any driver, you simply bend it downward. This can be done either by just flexing it like a taco, or by working your hands gradually around while bending just the rim. I prefer this latter method because it doesn't leave the disc looking like it just encountered a freight train. Fig 1 shows a disc rim being bent downward to decrease stability. Start at one place on the disc and repeat this bend about every 45 degrees around it until you are back where you started.

And of course, to increase the stability, you simply bend the rim upward (fig 2).

What's Happening?

Downward bending reduces the height of the outer edge of the disc and that's what changes the flight. Upward bending increases the edge height. It's as simple as that.

Many players whom I've taught about tuning have worried that the disc won't hold its tune but I can assure you that your disc will retain its tune very well. I often measure the heights of disc edges with a special instrument that I made just for this purpose (fig 3 below). It's accurate to one half-thousandth of an inch and has proven that discs hold their tune indefinitely. This instrument has been useful to my disc research, but you don't need it to tune your own discs. Just go out to an open field and start bending and throwing.

Of course any disc, tuned or not, will become distorted if you leave it in a hot car with a pile of heavy stuff on it. So, if you're serious about accurate flights, you should store your discs properly without any pressure that might bend them.

Most players have noted that well-used discs tend to become less stable with time. It's often thought that dinged edges are the culprit. However I've deliberately dinged the edges of discs and observed no change in flight stability. Thus I think it's likely that the disc's edge has simply been bent downward from accumulated encounters with trees, rocks and other hard surfaces.

Disc Materials

The least expensive discs are made from polyolefin plastic which is easy to deform. You've probably noticed that these discs ding more easily than the premium material discs. The easier a disc is to ding, the easier it will be to tune -- either deliberately or accidentally when scrunched under something heavy. Premium discs (including our new Epic driver) are made of more expensive elastomeric materials which resist dings. Thus they need more aggressive bending when tuned. Most premium discs require about three times the bending effort to achieve the same change in flight. So keep the material in mind when you tune.

Tuning In the Field

I recommend that you only tune your drivers on the practice field, never during a game. Label your drivers with a permanent marker for convenient reference during a round. You'll probably want to tune some drivers for neutral stability -- that is for level flight (with your arm speed) during the first three quarters of the flight. It's also worthwhile to tune at least one driver to be overstable -- for those upwind drives.

Some players like to throw rollers. As one fellow told me at the Master's Cup, "Roll is the great equalizer". You can turn any driver into a roller by severely tuning it with downward bends. Ugh, just the thought of ruining a beautiful flight makes me cringe!

Finally, if you're interested in distance competition, or the longest possible drives, you should try a slightly understable tune. That will cause the disc to roll over slightly beyond level -- but not so much that it ends up a roller. This type of tune reduces end- of-flight fade and extends the glide, but it's a bit more challenging to control.

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