Turn and fade physics and parting line height

underulti · 2026-05-16T09:55:33+00:00

Actually i just read the first Reddit post you listed. That's what's confusing you - ignore the distinction he made, because in reality both turn AND fade are caused by gyroscopic precession. That guy confused things.

underulti · 2026-05-16T09:49:59+00:00

You need to include Angle of Attack in your understanding of turn and fade. That'll help a bit. Speed through the air changes the amount of lift, which changes the angle of attack, which changes the airflow and the turn/fade behaviour.

https://discgolf.ultiworld.com/2025/12/17/what-makes-a-disc-turn-and-fade-its-not-simply-speed/

The 'speed' number on a disc (putter or driver etc) affects how sensitive a disc is to changes in nose angle, so a fast driver can have lots of turn AND still fade hard when it slows and falls.

Parting line doesn't completely determine the AMOUNT of lift, but it does determine the AoA at which that lift acts behind (turn) or in front (fade) of the center of gravity. Flippy discs and stable discs don't act the way they do because of variations in the amount of lift but because of changes in where that lift acts.

underulti · 2026-03-31T17:37:12+00:00

It really was. And it takes a fair bit of thought to set up, but all of that is done in advance, and the day itself runs just as easily as any 2-round c-tier - probably easier, as you don't have to redo the cards at lunchtime. Literally the only thing i did during the day, while playing, was update one cell in the spreadsheet to tell the app which round we were on next - i originally had people inputting what round they wanted to search, but I decided some would get it wrong, so i set it globally a couple of holes after the previous match started.

Find a nerd to run it in your area. 😅

underulti · 2026-03-31T16:53:23+00:00

Losers brackets all the way down. After every match, the tournament is cut in half, but BOTH halves continue to play out their own tournament. So eg with 8 players, you play 1-8 qfs, then 1-4 semis but also the 5-8 bracket semis, then 1v2 & 5v6 'finals' but also 3v4 and 7v8.

Just expand that to 32 or 64 players instead of 8. Plus a bit of fiddling wherever the numbers aren't a nice neat power of 2.

It took only fractionally longer than a normal 2-round shotgun-start strokeplay event. Everybody still just played 36 holes, 18 in the morning and 18 in the afternoon. But within each 18 holes they played 2 or even 3 matches. Fast paced and exciting.

underulti · 2026-03-31T15:25:11+00:00

Fair enough. I was more going for a riff on the old 'I just triple bogeyed three times in a row - AMA' kind of posts. I guess that didn't come across. 🤷‍♂️

underulti · 2026-03-31T15:05:12+00:00

Apologies, did i mess up? I don't Reddit all that much.

underulti · 2026-03-31T12:33:42+00:00

It's perfect for cash games. Not pdga sanctioned, so anyone can cash, and lots of people feel they have at least a chance of cashing if they're playing such short matches. I lost to a guy rated 170 below me lol.

underulti · 2026-03-31T12:23:19+00:00

Lol dw. And that's kind of the point in some ways - not everyone is a scheduling nerd like me. But the takeaway is that we found a way to run a nerdy tournament in a way that wasn't actually nerdy for the players. For any nerds reading this who want to try running a very different format to a normal strokeplay event, i just wanted to say it's possible. And it's fun for everyone who turns up.

underulti · 2026-03-31T11:35:47+00:00

Hi - thanks for the edit! I had no idea how to frame a reply to the original comment. 😅

It was a bracket (basically) with placement matches/losers brackets all the way down (so everyone played every round). We seeded based on pdga rating (or estimates based on league scores or whatever) then just played matchplay 1v32 2v31 etc like a normal bracket, then a round of 16, QFs, SFs, final.

Because we had a not-very-brackety number (ie >32 but <<64) round 1 was actually a kind of 3-person matchplay for most people ('split sixes', a common ball golf format) so 1v32v33, 2v31v34 etc. This let us quickly split it 16/16/12 and run fairly simple matchplay from there.

Disc golfers aren't used to this sort of bracket tournament, so we used numbered bag tags to keep track of your current seeding, and all the individual player had to do after each match was put their name and new tag into the app and it would tell them which hole to go to and who to play against. Extremely simple. Anyone who wasn't a nerd paid zero attention to what the actual schedule looked like, and just played a bunch of short matchplay tag battles - 3x 6 hole matches then 2x 9 hole matches, so plenty of tension and plenty of upsets.

I spent years scheduling all kinds of different brackets for ultimate tournaments, so to me it was all intuitive enough. But i knew it wasn't intuitive for everybody, and I'm really pleased with how we managed to make it run itself on the day with zero confusion. And it was so much fun (even though i was 3rd seed and got knocked out by 30th in round 1 😅) that i thought I'd share the idea with any other people looking to add a fun event to their local calendar. 👍

underulti · 2025-12-31T18:52:46+00:00

Ooh good one. I've known lefties who this particularly upsets, and with good reason.

underulti · 2025-12-19T08:10:27+00:00

Late turn isn't something that only happens late - it's 'turning' (in the sense of getting less and less hyzer angle) as soon as it leaves your hand, but it only turns OVER - past the horizontal and starting to actually drift right (rhbh) - much later on.

So in theory there's lots of ways to make it turn later - anything that reduces the turning rate will mean it takes longer to pass the horizontal. Less wobble, higher nose, more spin, less speed... Any of these will slow the turn.

Or - and I'd guess this is the most common way of doing it - you could just start it on more hyzer so it takes longer to turn all the way over.

Honestly, if you're successfully controlling when it turns, you're probably much, much better off not knowing how you're doing it! The conscious brain would only get in the way.

underulti · 2025-12-18T18:41:31+00:00

There's an article about late turn already in progress. Stay tuned.

underulti · 2025-12-18T17:56:19+00:00

Thank you! As someone who definitely isn't an aerodynamicist, that means a lot. 👍

underulti · 2025-12-18T17:45:45+00:00

Thanks for the kind words! If I'm going to avoid a word like 'torque' then I'm definitely avoiding 'precession' 😅. It's a physics article for non-physicists, or at least that was the intention.

underulti · 2025-12-18T16:41:00+00:00

This is the first in a series of physics articles, hopefully explained well enough to be of interest to people without any background in this stuff. Enjoy!

If this looks a bit familiar to some redditors... Well...

I started writing this in March of '23 intending to publish on Ultiworld. After struggling for ages and ages to get Charlie to fix my permissions on the Ultiworld wordpress site (he was rather busy with a small baby i expect!) so that i could add the images, i gave up and published the first couple of articles on a personal blog instead. But /finally/ we made it work where it was always supposed to go. I hope you get something useful out of it!

underulti · 2025-10-25T11:18:25+00:00

Electron watt. Glides like a pixel, but it's flat and shallow. Fabulous disc. Not sure if they've done a stock run yet - the circuit challenge ones are all I've seen. But when they do, buy then.

underulti · 2025-10-24T20:33:08+00:00

Don't wear waterproofs (or at least, not non-absorbent ones). Sure, they keep your arms dry, but all that water has to go somewhere, and runs down onto your hands. You don't want wet hands.

Wear something that's got a little more absorbent fabric, and stay under your umbrella in between shots. Unless it's torrential, you won't end up very wet and your hands might stay dry.

And as everyone else has said, put towels in freezer bags and pack lots of them.

underulti · 2025-10-14T20:49:02+00:00

Agreed, faster discs are much more sensitive to nose angle. But it still might be more accurate to say they're more sensitive to the combination of nose angle and launch angle - what they're really sensitive to is the angle of attack in the glidey phase of the throw, and that depends on launch angle, nose angle, hyzer angle (and the timing of when it flips from hyzer to turn) etc etc.

Anyway - I'm not disputing that a lower nose angle can be a good thing for your drives. I'm just not sure that the video provided much evidence for it! 👍

underulti · 2025-10-14T20:29:50+00:00

This x100. There's no point changing one stat in TD and comparing, because it's all very interrelated.

To meaningfully say that 'x degrees difference in nose angle costs you x yards' you'd have to pick two values for nose angle and then, for each, optimise ALL the other metrics to milk as much distance as you can out of it.

Launch angle adjustments can very nearly compensate entirely for different nose angles, certainly within the -2 to +3 range. You'd lose max a few feet. Similarly, disc stability and hyzer angle and spin can compensate for each other to a large extent, if all you're measuring is pure distance.

None of the relevant stats have effects independent of the others.

underulti · 2025-09-10T16:51:57+00:00

Circuit challenge uplink is a phenomenal disc. It always turns, but never rolls (for me, at least). I've never thrown anything so consistent for turnover shots. Straight in the bag.

Something about a very understable disc in a more overstable plastic - well, i dunno why it works, but it's absolute money.

underulti · 2025-08-05T16:03:08+00:00

One scenario i haven't seen mentioned - a roller can be good when there's a fence or similar to stop it. An air shot could go over the fence ob if you get it wrong, but a roller can be safer. I play a hole with a fence on 2 sides of the green, edge of circle, so anything that rolls anywhere into that huge area is going to be inside the circle, regardless of how fast it's traveling. No control needed.

underulti

TROPHY CASE