Observations On Disc Flight

 

 

OBSERVATIONS ON DISC FLIGHT

The modern golf disc has been designed and engineered to give the novice as well as the expert disc golfer a wide range of disc functionality to meet their skill and experience.  Understanding the design and engineering aspects of the disc and how these factors are designated, gives the player the opportunity to match the disc to their skill, experience level and course conditions to maximize the players performance and enjoyment of the game.

 

DISC DESIGN

The four-number flight designation was developed by INNOVA back in the ‘90s and has pretty much become the standard adopted by most manufacturers today to give players an idea of how their different models fly.  The 4 numbers quantify the four aspects of disc flight: SpeedGlideHighspeed Turn, and Fade (i.e. 9/5/-2/2). 

Flight Numbers

Description

Number Ranges

SPEED

Speed is mostly a direct result of the aerodynamics of the disc’s cross section.  Thus, thin sharp-edged discs will fly faster than thick blunt edged models. 

Speed currently ranges from 1 to 15.  1 being the slowest (Frisbie) and 15 the fastest (high speed driver). 

GLIDE

Glide is the second number and refers to a disc’s tendency to stay aloft as opposed to falling. In general, understable discs have a higher glide than overstable models.

 

Glide currently ranges from around 3 to 7.  The higher numbers tend to fly farther before  the fade takes over turning the disc in the direction opposite to the rotation of the disc.   

HI SPEED TURN

High Speed Turn is the third number and refers to what a disc does shortly after leaving your hand. This early phase of flight is the highest speed the disc will be flying at, since it will start slowing down shortly thereafter.

 

The High Speed Turn numbers currently range from around +1 to -5.  The lower number i.e. -5, the greater the tendency for the disc to turn in the direction of the spin shortly after release.  For a RHBH thrower this would be clockwise or to the right.

FADE

Fade is the fourth and final number. Fade refers to what happens at the end of the discs flight when the disc has lost most of its speed.

 

The Fade numbers current range from around 1 to 5.  Five having the greatest tendency to turn in the direction opposite the direction of the spin on the disc.  For RHBH thrower this would counter clockwise or to the left, etc.   

 

The four numbers are always listed in the same order Speed/Glide/Hi Speed Turn/Fade.
For example, consider a disc with 9/5/-3/1 flight numbers.  For a Right-Handed Back Hand* (RHBH) thrower, releasing this disc flat and at a reasonably fast speed, the disc will initially move 3 to the right soon after release and at the end of the flight Fade back 1 to the left. 

These numbers describe the flight tendencies of a disc assuming it is thrown flat and at a reasonably fast speed.  When the disc is released with an angle or at a low speed the numbers don’t really apply. Throwing the disc with angle is a means of shaping your shot and you will learn how the disc flies in these circumstances with experience.

 

MORE ABOUT DISC FLIGHT

The first number (Speed) is mainly the result of aerodynamics.  Generally, the higher the speed the higher the potential for more distance.  But speed is a double-edged sword.  The higher speed discs require more arm speed and a more precise angle of release or they may not even fly as far as slower models.  Speed should be matched to the players experience level.  It is generally recommended that new players choose drivers in the 9 speed or less range (until they can consistently throw 300’ with accuracy).

The second number (Glide) is highly related to the last two numbers (High Speed Turn and Fade). But it is the last two that are the most interesting.  These numbers show the gyroscopic tendencies, since a disc is much like a toy top spinning on its axis.  Disc designers noticed early on that by varying the distribution of weight in the rim and the flight plate caused the disc to rotate differently on its axis.  Placing more weight in the rim caused the disc to tilt in the opposite direction of rotation.  For a RHBH thrower (having a natural clockwise rotation) the disc with a heavier rim would try to tilt left on a disc making it overstable, for example (9/4/-1/3).  The reverse is true for an understable disc with numbers like (9/5/-3/1). The less weight in the rim causes it to tilt in the direction of its spin or to the right for a RHBH thrower.  And finally, when the distribution of weight reaches a happy medium as with a stable disc the numbers might be (9/5/-2/2). The rotation remains relatively flat until the very end of the flight were the disc usually fades ever so slightly.

 

OVERSTABLE – An overstable disc has a higher Fade number than High Speed Turn number. For RHBH* thrower, the disc has high tendency to fly to the Left.  For example, a disc with flight numbers 13/5/-1/3 would be considered overstable.  A short cut method for determining whether if a disc is over or under stable is to add the last two numbers in the flight numbers, in this case: -1+3=+2.  If the resulting number is positive the disc is said to be overstable.  If it’s negative it is understable, and those resulting in 0 would be considered stable or straight.

Overstable discs are usually recommended for the power throwers with considerable experience.  In the hands of an inexperienced player the results will usually be disappointing because the disc will fade so early in flight it really doesn’t go very far.

UNDERSTABLE – An understable disc has a High Speed Turn number that is greater than its Fade number.  For example, a disc with flight numbers 13/5/-3/1 would be considered understable.  A short cut method for determining whether this disc is over or under stable is to add the last two numbers in the flight numbers, in this case: -3+1=-2.  If the resulting number is positive the disc is said to be overstable, if its negative it is understable, and those resulting in 0 would be considered stable or straight.

Generally, newer players, players with lower arm speed or less leverage (shorter arms) usually find understable discs easier to throw.  These discs require less power and a less perfect angle of release to fly well.  You might say these are the most forgiving discs for players still working on their form. 

STABLE – A stable disc has a High Speed Turn number that cancels its fade.  For example, a disc with flight numbers 9/5/-2/2 would be considered Stable.  A short cut method for determining whether this disc is over or understable is to add the last two numbers in the flight numbers, in this case: -2+2=0.  If the resulting number is positive the disc is said to be overstable.  If its negative it is understable, but since in this case it’0 the disc would be considered stable or straight. 

 

DISC WEIGHT - There are some rules of thumb regarding the appropriate weight for a player’s discs.  A heavier disc is potentially more accurate and less affected by the wind.  The heavier disc flies better than a lighter disc into a head wind.  However, a heavier disc requires more power to accelerate its weight to reach the necessary speed to fly right.  A lighter disc on the other hand requires less power to reach proper launch speeds.  For this reason, players with lower arm speed, less leverage (shorter arms), or less form can usually get greater distance with lighter discs, but this comes with some costs.  The lighter discs are more affected by the wind and don’t do well into head winds.  The greater glide achieved through their lighter weight negatively affects their accuracy.  The lighter disc has less torque resistance and if thrown too hard may flip over (in the direction of the spin) and speed off out of control.

CHOOSING A DISC WEIGHT - Disc weights are usually written or stickered on the bottom of the disc by the manufacturer.  The Professional Disc Golf Association (PDGA) regulates all the rules for Disc Golf, including allowable disc weights (to create a level playing field).  And for a manufacturer to print “PDGA Approved” on their discs they must agree to abide by these regulations.  The PDGA regulations mainly limit the maximum weight for a disc, limiting it to 8.3 grams per centimeter of diameter.  The common weight range is from around 135 grams to 180 grams, but there are discs legal up to 200 grams!

There are no hard and fast rules for determining the right weight range for an individual.  This will take some experimentation to determine what’s right for you.  Your first rules of thumb will probably change as your game evolves.  Our recommendation is to choose putters and midranges near or at max weight (except for the very youngest children), since these discs are thrown for accuracy and the heavier discs perform better in more playing condition than their lighter counter parts.  Drivers are a place we encourage you to experiment.  Find the weight that goes the farthest and the weight that is most accurate for you.  Maybe carry a variety in your bag for different shots and playing conditions.

*All examples are for a right handed backhand or lefthanded side-arm thrower (RHBH, LHSA), others are the mirror image.