Why does saying "nice!" during the flight of the disc change its flight path?

Watched this as a break from my fluid mechanics homework and it didn’t feel like a break at all

Danny, thank you for the great content. Seriously appreciate your work. Wanted to illuminate some critical contributing factors for the decrease in stability from the "beating in" of a disc. The geometry of the "nose" (or absolute leading edge of the disc), the lower rim profile, and the rim bottom(either the bead or absolute bottom of the disc) contribute significantly more to the flight stability as compared to the small indentations and air boundary layer. As we throw a disc more and it contacts the ground or other surfaces, it wears away the rim bottom or the bead. This effectively decreases rim wall height and moves the absolute rim bottom closer to the leading edge of the disc, in relation to angle as viewed from a side profile. It also slightly changes the geometry of the lower rim profile. This is the major contributor to decrease in stability. The disc impacting a tree or other objects and bending the leading edge down while also creating a more blunt edge will have a similar effect. You do a great job of explaining the edge profile and how it contributes to flight in your video. This is the same concept. To demonstrate this take 2 identical discs and sand the rim bottom of one enough that you can tell a difference. Modify them in no other way. The sanded one will instantly become less stable. This works for all discs, but high speed drivers with a microbead especially. We can also observe this with the occasional disc that has a tiny "lip" on the rim bottom, often caused by the mold release process. Discs with this tiny sharp edge are more stable than normal. As soon as that edge is gone the disc will have a more usual flight pattern. You will see an increase in stability if you take a disc like the Freedom, which is silly understable, and sand the leading edge to an upward angle, in relation to the top of the flight plate. Air boundary layer, like with golf balls, does contribute, but to a lesser degree. Likely it contributes more to a decrease in air resistance. I think we see this with Lat 64 Raketen and Misselen. They have "Hex technology" to increase the air boundary layer but we don't see drastic decrease in stability

Thanks Danny. I was really interested in your two previous videos on the topic, but I was also thinking something was missing. This really clears it up, is helpful, and I'm taking some notes.

I want to thank you for your older videos that help me to play better. I'm a new player searching for info to get better

This video is a gem. This comment section is a library. Thanks guys for discussing there topics so much. I really learn a lot. And thank you @Danny Lindahl for making videos like this, teaching and sharing your theories and engaging in the discussion.

The tendency for a fluid (air is a fluid) to adhere to a surface is called the Coanda Effect for reference. Good video sir.

Very enlightening. Can’t wait to repeat what Danny says to my disc golf friends to sound like I know what I’m talking about

That’s very interesting! :) Thx for talking about those topics!

Nice video. Keep up the good work :)

I'm with Jacob. I think precession explains the disk behavior in some realms of flight. The roll force of the disk is the cross product of the gyroscopic and lift vectors. The relative strength and direction of the two vectors changes in flight so that a component of lift is at times perpendicular to the spin vector, causing turn or fade. Throw the disk at the designed speed with designed spin, the vectors are colinear and the disk flies straight. Overthrow the speed number, the lift vector shifts off axis a little and it turns. Underthrow and it fades. Danny's explanation may be better for low speed fade. Great post. Danny, your video on keeping my shoulder joint at 90 degrees when throwing was a magic key for me. Seems simple but all you hear from the other vloggers is snap and reach back and blah blah blah. Nothing helped til I saw your vid. Now Ezra has now come out with a video on this point. Check it out.

Good vid Danny! The upward pressure causing tilt is true. This point of pressure is key to freestyling. When you nail delay, you are constantly moving your finger 90° into the spin. Thumb pressure on the flight plate can setup a pressure point that is the "center of spin". In order for this "center of spin" to return to the center of the disc, the disc will turn over. It is the nature of a gyroscope. Again...Good vid! On point!

A beat up disc is also more rounded meaning the air generating lift has a steeper angle Since the lift is shifted to the side by the spin (like you explained) the left side of the disc on a backhand is raised slightly more compared to a new disc

Hey Danny, can you do a video about "How much Damage can my disc take"? I'm curious about whether some of the dings and nicks on my discs are affecting the flight enough that I should scrap them.

You make excellent videos. Something that's seldom talk about is to throw up and down hill. Disc selection. How to practices and so on

nice content danny!

The term you're looking for at about 7:00 of the video is angular momentum. Spinning objects require a torque perpendicular to the axis of spin to change the angle of the spin axis - this is what causes turn. Basic physics of rotational motion.

This is a very good explanation Danny I think you could be helped by pairing it with some animations!

I didn’t think I was going to understand...well done

Thank you for this.

Cool stuff but I have some points I like to get in: 1) Your first idea of how discs generate lift is correct, they do generate it by air passing over the top faster than it passes over the bottom (the bottom is shielded from airflow by the rim so the airspeed there isn't much at all) but a disc is the worst form of "wing" you can have since practically all of it is subject to wingtip turbulence. Although the airflow "turning down" behind an understable disc can have an effect it is too closely linked to the dome of the disc to consider separately since greater curve = more airspeed which results in lower pressure. Airspeed leaving the disc also facilitates high airspeed over the middle since the airflow "wants" to stay connected because of its own inertia (this inertia means its a bit of a "bump" go from a smooth airflow to a turbulent one) 2) I disagree with your spin analysis for overmolds: the difference in spin won't be worth mentioning if you just shift weight 10% closer to the rim but the main part I really disagree with is spin retention... discs don't really lose spin to a noticable degree while airborne. All of the changes to the flight trajectory happens as a result of losing speed which causes loss of glide which causes the disc to "fall" and thus fly "nose up" relative to its direction of travel, hence more loss of speed leading to the fade, having the weight closer to the rim will counteract the turn and fade slightly better but is far less important than an overall good discdesign. 3) Your turn/fade analysis is spot on however although the segment you cover it in here is mainly for new discs. 4) I strongly disagree with your opinion of beat in discs and why they behave the way they do. It has almost nothing to do with "dimples" or pits from impacts but everything to do with the disc becoming slightly warped upon impact, each impact creates its own microwarping of the disc kindof like a bicycle wheel after years of use without anyone realigning the spokes. This yields an uneven flightplate which causes increased lift on the side that is spinning against the air (just like a helicopter prototype before they figured out how to realign the rotorblades to compensate for airspeed) this "different" understability has the added benefit of pushing the nose up late in the flight which can help stretch it a little bit and land it softer. For examples of "dimples" in discgolf you can see if Anthony still has a raketen or missilen in his disc collection and you can experience firsthand how proper dimples speed up the disc a bit but totally guts the glide.

Great video!

That was great thanks

hey danny thanks for your vids

You and Smarter Everyday need to get to the bottom of this.

I've kidnapped Danny so he would be forced to give me private disc golf lessons. I will let him out of my basement once I've broken 1000. Until then, no more videos.

it's vector multiplication. multiply the lift vector by the tangential velocity vector and you can visualize how as the disc flies it will start to tilt. hyzer for overstable(RHBH) and anhyzer for understable (RHBH).

Hey Danny I've been disc golfing for about 6 months and have really progressed and play everyday I'm throwing at max distance about 400 to 450 on a rip with a wraith or a beat in destroyer or g-star one is there any recommendations for when you hit a plateau cuz I know it's probably just in my mechanic some of my timing and bracing a full run-up I'm only doing a three-step I feel really comfortable doing it any tips would help thanks

yep, that's why it fades, good explanation. and further this is why nose down decreases it's fade

Danny keep studying the physics of disc golf! Do you think a nose down angle could take a disc further distant with a tail wind given the lift will be with the wind and really send it?(Even though a tailwind gives an effective slower speed and headwind faster) I noticed that a nose up occurs because the backside of the disc at release may have drop slightly due to gravity. Thus nose up and high stall left. Lots of frustration. I have not heard anyone talk about all that weight at the back and the wrist not strong enough to keep the rear higher to prevent nose up. Thanks

Hey Danny, wanted to touch on what you said about Overmold as I kinda nerded out on this yesterday. You are correct in saying that moving the center of gravity away from the center of the disc does make it harder to put the same amount of snap on a disc as one that has a more central to the disc. Here is what you missed. If you get 12,000 RPMs on an overmold and 15,000 on a regular disc, and assuming the gyro is designed for 12,000, regular is designed for 15,000, the gyro will experience less turnover due to it being harder to add more spin, and easier to flip the regular disc. Then, the progression down to zero rpms would be slower for the overmold due to the weight being further from center and traveling a greater circumference. Think E=mc^2. Any distance change is squared so it does have a big effect on how the energy dissipates , and that explains why the flight lines between discs like the Envy tend to have very straight lines while not requiring as much hyzer to flip to center. This also makes it so they don't over turn too far to the right or left if you put it on a good line. Meanwhile the same shot from a Luna or P2 might be easier to get the disc to turn as well as have more fade if the disc loses too much of it's rotation. Ideally, overmold should lead to more consistent flight, but there are situations where players want that big turnover S curve or they want to put a ton of hyzer on a flip up. So in the end you are right about preference, but the overmold aspect does effect the flight of a disc and how you throw it. As always I appreciate all the effort. Keep up the great work!

Great video. Interesting topic, wouldn't mind a updated opinion on this subject. 🤔

Hey I was wondering if you do form checks, I throw about 275-320 with a Zeus and I want to get to a 350-400 range, if you do I will post a video somewhere after you comment thanks

I think that gyroscopic precession is key to understanding the physics of flight, and I am happy to see you tie turn and fade into this. 🤓👍 When I first heard about it on Vsauce, he seemed to claim that the angle, with which the tilt is turned away from the flight direction, is 90 degrees. Do we know that it is 90 degrees? Or does it vary with the speed of rotation and the velocity of the air flow around the disc? (Really nice video!)

One of my best friends is Steven Holmquist from little rock, Ar. i Recently got into disc golf and he mentioned you!! Thats INSANE!! Small world haha. Hope you see this 👍🏻

My theory on beat in discs is that the left side of the disc is at higher pressure because it is pushing air forward. The right side of the disc is at lower pressure because it is pushing the air backward. This causes a pressure differential between the left side and the right side of the disc. Therefore, a force pushes the disc from left to right. I’d say this is different than gyroscopic precession. It’s more of a sliiide to the right. The same thing happens to golf balls but since they spin backwards an upward force is generated.

Danny .. hoping for an upload soon!!!

What if you had a disc with its flight plate concave ? Could a flat backhand become an instant anhyzer?

How to add more spin to your throw?

If you have more spin on a disc will it make it turn and fade less? Both overstable and understable discs

The tree hits also lower the parting line, adding to the lift talked about earlier in the video.

5:33 dannys got an albino cheeto puff on his hand

How are discs designed currently? Do the designers have some general idea of what shapes give certain characteristics, then they try them with wind tunnels or how does it work? I was thinking of giving a PhD offer to my university in how disc shapes affect flight characteristics, and create a model to predict these flight characteristics by simulating air flow around the disc, using something called "finite element methods". The idea was also to possibly later create an algorithm that can engineer discs given certain desired characteristics. Do you think there would be an interest in this from the perspective of a disc manufacturer? Anyway, really cool that you took the time to dive deep into the actual "physics of flight". I think it was on point, and interesting take on understability of discs due to wear. I think it's likely that the irregularities in the surface decrease spin rate and results in less gyroscopic stability.

Had me until you substituted "glideier" for lift at 2:41. Lift is created when the air over the top is faster than the air underneath. The felon causes the air underneath to be the same speed as the air over the top. Lift is what makes an airplane wing go up and the airplane lifts off the ground. 2:41: "Understable discs are more glidier" because...why? "Domeyer discs are more glidier for the same reason" what is the reason??? Are you saying that "GLIDE" is based on lift???

Hey Danny. Wile you may be right about the nicks and dings on the rim I always thought the flight changed on a disc because you hit trees and bend the rim down a little bit with wear an tear witch causes more down pressure on the nose. Am I wrong or does this also affect the flight

What is it about a disc that makes it curve this way or that way? After an hour and a half of futile search on the marvelous internet highway, I finally have a somewhat simple answer. Thank you Danny.

I actually think the Bernoulli Effect still applies and is linked to the explanation with the "downwards directed air". The latter is just the same result being explained with Newtons law of Inertia instead of the Bernoulli Effect: the Inertia of the downwards directed air must be equalized by a counterdirected inertia (=Newtons law), this results in a pressure gradient which lifts the disc up (=Bernoulli Effect). It is, so to speak, the same phenomenon being explained from 2 different perspectives. However I´m not an expert in fluid mechanics, so I´m not 100% sure if that is acurate :)

"people and their.. packages" gachiHYPER

So that’s why the discs with higher “glide” seemed more understandable, and Vice versa

When you coming back bro?

I find it strange that this video has less than 500 likes.

Hey man, are you supposed to try and snap the disc like snapping a towel? It’s hard to follow through and do that.

Wait.... overstable discs have less fade as well??? 🤔

Now the big question..should I rough up the edge of a new or newer disc for that beat in feel? 🤣😂🤣

Where did you go

Impressive.

Negative pressure under the wing

The best frisbee for staying aloft is a petco 1.99 special. I throw it from my hip and snap my wrist it hangs in the air for several seconds on a calm day

Hey Danny, I appreciate you tackling the flight of discs. I love science myself, and so like it when other people look at things the same way I do. I also think knowing how a disc flies really does help when making decisions out on the course. Also, there is a great video by the D!ng channel, that talks about the procession of rotating objects. I think it would help you explain to others why discs turn and fade. Here is a link to that video, kzfaq.info/get/bejne/fdCXfNCku9e0lps.html. The most helpful part starts at the 6:00 minute mark.

"angular momentum" - dunno how you did this entire thing without saying angular momentum! Nevertheless, fantastic video, and shocked to see it doesn't have a lot more views. I wonder if anyone ever made a disc with sensors in them to record spin dropoff over the course of a flight (could also do it with slowmo camera and ink), or stuff like wind tunnels to test discs like they do jets & automobiles.

Love the cat

Dimpled discs coming soon!?

Yeah due to spinning the force takes place 90° later in the rotation Helicopters take this principle into consideration

Makes sense, I think one thing you may have glossed over was variable of spin velocity. Spin and release velocity amplifies the "friction/turbulence factor" (sidearm spins faster than backhand, while backhand has higher release velocity) flight velocity(t), spin velocity(t), turbulence(t), friction(shape and "beat in"). these series of videos by "best disc golf discs" also break it down well : kzfaq.info/get/bejne/e5NgobZ905etiGg.html

How about the physics of how altitude affects flight?

Can someone post a link to the discord?

I love your dedication to the sport, and to the variety of disc brands available to the public. Why do you think, given your obsession with the sport at this point, that you haven't been able to break into tier one yet?

I can't disagree with the turbulent air argument. It makes a lot of sense. When I was looking into beat-in discs, I found that the more important part is that the nose gets pushed/bented down, making more of an understable disc shape. Not that it's helpful today with premium plastics, but disc tuning used to be a thing; I.E. Aerobie Epic.

I've read some white papers on this and at least the terminology is and to some extent the theory has been completely different. (sry I can't find the paper now, but I can try to look for it) 1. I read that the lift would be the result of lower air pressure on the top of the disc lifting it up. This is caused by a longer route for the air to travel on top of a domed disc than below it. 2. I read that turn is the result of the left (RHBH) edge of the disc having more velocity and as a result having more lift than the right edge 3. I read that the fade is the result of gyroscopic force when the disc slows down and its nose lifts up, turning the left wing (RHBH) down due to the said effect Bonus: Everyone has read that in vacuum all objects fall down just as fast ;) Regarding the beat up discs, I think you are correct with the "pimple theory" but I definitely have some drivers where the wing has been bent down from a tree hit and made the disc very understable. Another factor that is HUGE on trilogy discs is the flashing. As the flashing on the bottom of the rim wears off, the tip of the wing effectively comes down as well making the disc more understable. I've tested this personally on a couple of your drivers by throwing them, then removing the flashing and repeating the throws. This effect is way more drastic that the gradual wear of the surface. It is most noticeable on premium plastic drivers.

basically center of lift = stability. more lift

Putting more weight on the outside of a disc like an overmold disc, does not on its own make the disc spin less. What it does is make it harder to spin the same amount. The effect is less spin, but the reason is different. Also, the arms analogy is not correct. When you put your arms out while spinning, you are making your circle bigger which slows down spin. Discs are near the same size, so that example doesn't work. Overmold certainly has an effect, but whether that effect is significant is what we need to discuss.

I'm here to watch the cat wander around. 😁 What is the cat's name?

It's important to denote the difference between rotational inertia (aka moment of inertia and linear inertia aka mass), so a disc that has a larger rim will have a larger moment of inertia because the mass is more concentrated further away from the axis of rotation (radius r). I have not seen any actual experimental validation regarding why a disc fades left (RHBH) or right (LHBH). Just doing math on the back of a napkin, it might be explained by relative velocity effects on the sides of the disc inducing a torque disparity.

Okay...but aeronautical engineers are still arguing about which theory of how airplane wings generate lift is correct? I am not certain that we should take all of this to the bank yet.

Your original interpretation of lift was correct. Since the air has a longer flow path over the top of the disc relative to the bottom it speeds up because it is basically trying to equalize the air pressure differential caused by the disc moving through the air. As the air speeds up over the top of the disc it's density decreases, you wind up with lower pressure above the disc than below, causing an upward force on the disc. A domier disc will have more lift than a flatter disc because the air has a longer flow path over the top causing it to speed up more and thus a greater decrease in pressure. The comes a point where the curve is too dramatic(or the speed is too great) and the air can no longer follow the curve, causing a loss of lift due to disruption/separation of the air flow.

Overstable discs fade less? Who knew!?

Hi Danny. Forget flight physics - it just doesn't matter. In fact, the reason planes stay in the air is because the wings deflect a mass of air downwards that is equal to the mass of the plane (in level flight). Bernolli lift makes wings efficient, and offer increased flight performance over a wide range of airspeeds. But there's no problem making a perfectly flat aeroplane wing, they just don't handle very well.

OMG no! You had it right to begin with. It's the Bernoulli principle. A combination of rotation and forward momentum is what causes lift, specifically because the wind going across the top is moving faster across the disc. A disc works much like a helicopter moving from a hover to transient flight. Turn is caused by a principle called dynamic turnover. The faster a disc spins, the more sensitive it becomes to its stability. When you couple this with forward momentum, the leading edge(left side) of the disc will generate more lift than the trailing edge(right side), thus causing the disc to turn right. Please read up on how a helicopter flies, you will understand this better. 🤦

Someone make a dimpled disc

Ur a trusted content provider with a relatable style but you bit off too much. This topic is best left to experts and ur anecdotal tales are confusing players. There's a reason the community keeps putting out flight videos. We're still evolving our base knowledge without definitive empirical flight data. Static wind tunnel test and wing shape comparisons don't cut it. Some day we will have data that will end one arguement and start another. I've asked Veritasium to do real disc testing to help our community. I believe he has the skills to rescue us from applied guesswork. Ditto to the technical detractors to some of ur claims. If you want to impress playing partners with smarts, say "inertia " or "gyroscopic precession". Or ace it.

Modern day Bill Nye

Your pretty close on beat in discs, the imperfections in the rim expand your air your air cone on the disc if you look at cars and other objects made to cut through the air, bigger air cone the more air molecules put in motion it lowers the air friction on the disc bc much like breaking surface tension of water breaks the static tension of the air and wind. So with the fluid motion of the air around your disc you have less force against the nose of the disc

Did Scott Stokely put you out business?