[Question] Disc Rating Differences- what physical difference?

[dandechino]

I understand there are significant differenced between a putter, mid, and driver. Then within each type there are various molds with slight differences to produce different speed, glide, and stability ratings.

Say, between a speed 9 and speed 10 or 11 or 12 driver disk what physically changes in the disc molds?

What makes the disc have more glide than another?

What specifically factors into a disc's stability either over/under?

 

[august dupree]

Unfortunately, there is no easy answer.

 

[BogeyNoMore]

If I told you, I'd have to kill you...

 

[wims]

The speed of the disc is largely based by the rim width. Typically the speed of the disc is the rim width in millimeter - 10.

The glide of the disc is typically dependent on the dome; the taller the dome the more glide ... in most cases anyways.

The stability is typically based on how far the tip of the wing is from the bottom of the disc. A very understable disc like the Mamba or the Tern has the wing very close to the bottom of the disc. A very overstable disc like the XXX or the Firebird has the wing very far from the bottom of the disc.

These are generalisations and there are many examples that don't follow these general guidelines

 

[Jax11]

I can't give any scientific support or reasoning but here are some general observations:

- Rim width = speed of the disc - wider rim is a faster disc
- Higher dome usually equals more glide
- Wing profile and shape from mold to mold affect stability (haven't noticed any specific trends)
- Parting Line Height can affect stability. I believe the higher the parting line the more overstable.
- Stiff discs are more overstable than flexible discs

I'm sure everyone can find a disc in their bag or collection that breaks these generalizations, but these are some general trends I have noticed.

 

[Pbmercil]

Speed is generally proportional to the width of the wing. Wider wing = faster. It varies a bit from manufacturers as to the exact wing dimensions and speed.

Overstability has two main factors. Wing height is one. The closer the edge of the wing is to the top of the flight plate the more overstable the disc generally is. Also the shape of the wing's edge matters, a blunt wing is almost always overstable.

Glide is argued about to death. In my opinion glide and stabilty are inherently linked, tho they may not be exactly proportional. A more overstable disc will always have less glide because its stability wants to get the disc to the ground faster.

These are all decent generalizations. Their are absolutely exceptions to all of these ideas, but its a decent starting point.

 

[august dupree]

Some good reading here on the subject of plh from back in the day...

https://www.dgcoursereview.com/dgr/...sid=39cfd8a5586c2d8195f3d6bf95d032e7&start=15

 

[armiller]

Depending on how much you want to get into physics these discussions can go on for a while... there are a couple recent threads in the Technique section, and some much older ones hanging around too... There are practical factors like PLH and stage of wear that play a part, and then there are more scientific things as well. I'm on my phone so I won't post links, but john63 posted some nice PhD theses in "Disc Golf Physics 101" or some similarly named thread. One of the papers compared a Wraith, Flick, Buzzz, and Aviar. One thing that struck me is that the Buzzz center of pressure was much closer than the Flick's to the center of mass. I think that's one of the main things that makes a disc overstable: COP farther from COM.

As far as glide, it kinda depends what you mean. Is there much rhyme or reason to how companies rate their discs? I doubt it. But as far as how well discs glide, it probably has to do with how the lift coefficient looks at different (especially higher) angles of attack. Also, if that lift force acts far from that center of mass, it will probably reduce glide by making the disc fade more.

 

[ThrowBot]

A few observations about some specific geometric features:

The more concave the bottom of the wing is, the more overstable a disc is. Look at a firebird or banshee which have noticeably concave wing bottoms, compared to a roadrunner or heat which are very straight (or even slightly convex).

Also, it seems like beaded putters and mids tend to act more overstable. Aviar P&A vs. Aviar Driver is a classic example of this.

(These generalities are also affected by parting line height, which has been well covered above.)

 

[SD86]

What everyone above has said is generally true.

One comment about glide: I look at it from the perspective that glide is what keeps the disc flying after the applied power that moves it forward has been offset by the drag of the air; IOW, the air beneath it keeping it up as it continues on momentum (body in motion staying in motion, and all that stuff).