This episode of our Video Guide Series features an ADVANCED explanation of disc golf disc GLIDE numbers, including the conditions that impact Glide and the four scenarios in which you will always want to use a high Glide disc (full video transcription provided at the bottom of this post).

Links to Resources Mentioned in this Video: 

Disc - Tern ChampionInnova Discs – Flight Rating System

Lift Coefficient – Complete Explanation

Effects of Temperature and Altitude on Lift  – FAA Report

Airspeed vs. Groundspeed – Complete Explanation

Innova Tern – Get one for your bag

 

Full Video Transcription:

Warning: may contain minor transcription errors, and definitely containing the grammatical errors I use when speaking!

Welcome to Best Disc Golf Discs Video Guide Series. In this episode we’ll be covering:

  • What is Glide
  • How Glide affects disc flight
  • When to choose high or low Glide

According to Dave Dunipace, the inventor of the modern disc golf disc, “Glide describes the disc’s ability to maintain loft during flight.”  He also describes Glide as “the amount of lift a disc has, usually compared to other discs in the same speed category.”

To explain the concept of lift on a disc in flight, the weight of the disc is, of course, pulling it down, and the opposing lift force is what’s keeping in flight. The concept of lift is where we will be spending a lot of time today as the amount of lift generated by the disc is where it gets its collaborating

To understand how the Glide rating fits into the big picture we’ll need to understand “lift coefficient.” Expressed by this complicated formula, it breaks down into: lift is a function of the air density, the airspeed, and this group of variables at the end (essentially combined to create our Glide rating).  Restated, the total left of the disk = the air density X the airspeed X the Glide rating, so anytime one of these three factors in yellow increase, you will have more left and when one of these factors is decreased you will have less.

Lift is obviously an essential part of disc golf flight, and while it is critical to distance too much lift can create a disc that sails high, loses speed quickly, and changes its line unfavorably — so the question becomes “when should players use high Glide?” We found four situations.

The first reason for using high Glide is for extra distance.

Because of the exponential relationship between velocity and lift, players who throw with low velocity will need extra Glide to give them more distance. This includes:

  • Beginners
  • Low-Velocity Players
  • Any player who is in trouble and can’t get a full throwing motion into their disk

While all players will benefit from good glide on their drive, high power players drive with moderately High Glide disk such as a Destroyer or Wraith, and you would rarely see a professional using a maximum Glide disc.  This is because their extremely high release velocity combined with maximum Glide would generate too much left.

The second time to use High Glide is with a Tailwind

During our video guide on disc selection and wind conditions, we spent a significant amount of time talking about Headwind, Tailwind, ground speed, and AirSpeed (and we highly encourage that you watch that video to get more information on this concept) but anecdotally speaking if you’ve ever thrown a styrofoam airplane that normally would fly like this, thrown into a headwind that same styrofoam airplane move line something like this: immediately surging up into the sky. This is because headwinds increase the amount of lift that objects generate, so you’ll want to decrease the amount of glad you’re using to compensate for that.

Conversely, because Tailwinds decrease the amount of lift something generates you’ll need to increase your Glide to compensate.

The third case scenario we found is when air density of low.

Aerodynamics is defined as the interaction between molecules and solid bodies moving through them, and low-density air has relatively few molecules per a given unit of volume.  For this reason, thin air=low lift.

High heat, high altitude — use high glide

The fourth scenario for considering highlight line is with heavy plastic.

We will use the Innova Tern as an example. It’s often regarded as a very high Glide disc. The Tern is available between 130 and 175 grams — the way that these manufacturers do this is with the density of the plastic.  The size and shape of the disc do not change and therefore the lift force does not change as the weight changes…. however….

As we discussed because lift and weight are opposing forces if list remains constant but weight changes flight line will change as these two are thrown out of balance.

Let’s say you’ve chosen to play with the 150-gram Tern and at 60 miles per hour it flies perfectly straight, meaning that the lift force and the weight are an equal balance. Now let’s say you choose a 130-gram disk. Because the lift is the same but the disc now has less weight pulling it down, the flight line will shift up as it generates more left than the compensating weight.

The key point to remember is that with any specific desk using a lightweight version of the disc increases the Glide effect and using a heavy version decrease the glide.

Summary:

  1. Use it for extra distance but high power players should use caution
  2. With the Tailwind but never into a headwind
  3. When the air thin, is typically at high altitude or with high heat
  4. Or based on the disc weight.  Light desks have more Glide impact.

 

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4 Comments

  1. Jeramy

    Reply

    The discussion about disc weight and how it affects performance got me wondering. I live in Denver, and here the air density is about 80% of what it is at sea level. If I’m building a starter disc set based off this site’s recommendations (Valkyrie, Roc, Aviar), should I be choosing a lighter version of each disc, or should I build a different set? The idea is if I do travel — I have family in California — I’d get a set for sea-level and a set for high-altitude, but of the same molds for predictability.

    • Bart Bird | Site Manager

      Reply

      Jeramy – that could certainly work, just keep in mind that when you change weight classes (with the same mold) your release velocity is affected which will typically change the amount of turnover you get.

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