Disc Flight Question

[Cigarman]

If I throw a Aviar P & A perfectly, at a speed which makes it go 240 feet, per the charts it will go straight during the high speed stability part of the flight.

My question is, if I throw it at a speed which makes it go 500 feet, will it turn or still go straight during high speed?

Second question, say I throw it only 200 foot speed, but spin it 2 million RPM, does the spin contribute to 'speed', or just more gyro effect?

 

[Chromezero]

I'm certainly no expert, but here's my observation over the years...

If you throw it at 500 feet worth of power, overpowering the disc, it will turn more than it's rated. Conversely, if you don't throw it fast enough, it will appear to be more overstable than it's rated. Now as for the spin, I don't believe it contributes to the "turn" or "fade" directly. However the more spin you have, the longer the disc will stay at the initial launch angle(hyzer or anhyzer). This, in turn, can effect the overall flight. So, it will turn(more or less), fade(more or less), but for different reasons than speed.

 

[clard]

If I throw a Aviar P & A perfectly, at a speed which makes it go 240 feet, per the charts it will go straight during the high speed stability part of the flight.

My question is, if I throw it at a speed which makes it go 500 feet, will it turn or still go straight during high speed?

It all depends on the particular disc how much spin is on it. Simon Lizotte can throw a p2 which is a slightly more stable putter 400' and it won't turn over. Some discs are much more speed sensitive. Let's say we are talking about a Valkyrie. If you throw certain Valks with 200' of power they will hyzer out early, 250' of power they will hold flat then hyzer out, 300' you might get a little turn, and at 350' you would have to start it with some hyzer to avoid it turning all the way over.

Second question, say I throw it only 200 foot speed, but spin it 2 million RPM, does the spin contribute to 'speed', or just more gyro effect?

Spin doesn't contribute to speed, but spin will keep the disc on the axis it is spinning on longer. E.g. more spin would make a disc thrown 200' stay on whatever axis it was released on until it hit the dirt. Then it would probably be spinning so fast it would light the grass on fire and the disc would melt

Not to say you shouldn't pursue these questions, but talking about speed vs spin is interesting more in theory than in practice. If you work on good form and getting a clean release you will generate enough spin and speed without "trying" to spin the disc.

 

[Cigarman]

Theory

Not to say you shouldn't pursue these questions, but talking about speed vs spin is interesting more in theory than in practice. If you work on good form and getting a clean release you will generate enough spin and speed without "trying" to spin the disc.

Thanks for the replies. Very true. I guess I'm just looking to the future should I ever get there to know which 'speed' discs are appropriate. Some times the Aviar turns a little but probably due to release angle. The Leopard never does, so I doubt I'm even close to speed or form to worry about progressing at this point.

 

[ToddL]

If I throw a Aviar P & A perfectly, at a speed which makes it go 240 feet, per the charts it will go straight during the high speed stability part of the flight.

My question is, if I throw it at a speed which makes it go 500 feet, will it turn or still go straight during high speed?

Second question, say I throw it only 200 foot speed, but spin it 2 million RPM, does the spin contribute to 'speed', or just more gyro effect?

Don't worry about spin. One, you can't control it all that much, and two, it's not nearly as important as speed. If you're able to throw it fast enough, it'll be spinning enough as well.

As for your main question, it depends on the disc. Like Clard said, a slow Valkyrie will hyzer but a fast Valkyrie will turn over. A slow Mako will fly straight and a fast Mako will also fly pretty straight. It's a function of the aerodynamic design of the disc. If the center of lift moves a lot as velocity changes, then the flight speed will matter a lot. If the center of lift doesn't move much, then the flight speed will matter very little. Of course, can you tell the difference just by looking at the disc? Probably not. You kinda have to trust those flight numbers

 

[clard]

Thanks for the replies. Very true. I guess I'm just looking to the future should I ever get there to know which 'speed' discs are appropriate. Some times the Aviar turns a little but probably due to release angle. The Leopard never does, so I doubt I'm even close to speed or form to worry about progressing at this point.

When you get there you will know. Once you are throwing a decent distance consistently you will be able to throw a disc a couple dozen times and understand how it behaves on height, speed, and angles.

Worry about progress, but not discs. If you are interested in throwing farther and better have us take a look at your form. As your form gets better you will understand discs better, and then you will be able to figure out the discs you need. (Says the guy who has shelves full of discs...)

 

[Dan Ensor]

My take is that a disc can fly under cruising speed, at cruising speed, and over cruising speed. For each of those, it has a certain flight characteristic.

It doesn't really matter how much above or below cruising speed it is, though. A 0 turn Wizard, for me, doesn't turn at 200', 300', or 400' (If I could throw it 400').

 

[mashnut]

My take is that a disc can fly under cruising speed, at cruising speed, and over cruising speed. For each of those, it has a certain flight characteristic.

It doesn't really matter how much above or below cruising speed it is, though. A 0 turn Wizard, for me, doesn't turn at 200', 300', or 400' (If I could throw it 400').

I think you'd see a lot more variation with a disc that was more speed sensitive though. Discs like the Wizard, Roc and Teebird (and to some extent a disc like the Destroyer) are great discs partly because they're so flexible speed wise. You can get useful lines out of them without much power but they don't get squirrelly under a ton of power. Something like a Vulcan on the other hand is going to have a much more noticeable change from barely over cruising speed to way over cruising speed.

 

[Dan Ensor]

I think you'd see a lot more variation with a disc that was more speed sensitive though. Discs like the Wizard, Roc and Teebird (and to some extent a disc like the Destroyer) are great discs partly because they're so flexible speed wise. You can get useful lines out of them without much power but they don't get squirrelly under a ton of power. Something like a Vulcan on the other hand is going to have a much more noticeable change from barely over cruising speed to way over cruising speed.

I can see that. So maybe it's

(HSS)*(MPH over cruising speed)=Flip

?

That doesn't work for a Nuke OS or something, though.

 

[slowplastic]

+1 on Mashnut's post.

Basically a disc that has some shape to its flight numbers (like -1 or more turn) and some fade, generally will change characteristics more at different distances. And the faster the disc, generally will change characteristics more.

As said, Aviar/Roc/Teebird are great because they are fairly slow discs, so at low speed they hold pretty straight and they don't have that much fade, but as they are thrown harder they all have a 0 for turn so they stay pretty straight for HSS, but the fade becomes more minimal.

Discs that are faster and have 0 turn and lots of fade will stay straight the whole way, for the most part, like a Firebird or XCal or something. If their speed is very exceeded they may show a turn, as some people can turn XCal's even though their HSS rating is a 0.

Fast discs with some turn numbers (like a Vulcan, as was mentioned) will act very different at different power. It is speed 13 so needs to be thrown hard or else it may act like 0 turn and 3 or more fade. Once up to speed it will see a drastic change in HSS, where it has a lot of turn, but will still fade forward. Exceed the speed too much, and it can very easily ride the hairline between huge turnover and long range roller. This is an example of a speed sensitive disc.

Opposite to that is a Destroyer, which is also fast, but has a little turn and a medium fade. The harder it's thrown, it will have a bit more turn, but usually fade out reasonably. This disc does change characteristics with power, but not anywhere like the Vulcan.

So basically it varies mold by mold, but in general the faster the disc and the more turn in its rating, the more you can expect it to change characteristics with power level.

In conclusion: keep throwing the Leopard and get a Teebird too. When the Leopard is flippy and the Teebird is still going straight, you'll know you're doing well.

 

[wims]

...
Spin doesn't contribute to speed, but spin will keep the disc on the axis it is spinning on longer. E.g. more spin would make a disc thrown 200' stay on whatever axis it was released on until it hit the dirt.
...

I keep reading that, but the aviation enthusiast in me is a bit puzzled about it. I would think that the spin creates increased airspeed over the left side of the disc compared to the right side of the disc. This increase in airspeed should lift the left side causing the disc to turn. Once the disc loses speed and spin the air friction of the disc spinning will overcome the lift forces causing the wing to lift and the disc starts to fade

Exactly what makes the disc fly more stable when it spins?

 

[slowplastic]

^I don't know the physics explanation for this gyroscopic stabilization, but my experience is also that a disc with more spin generally holds a stable (meaning straight) flight for longer. Too much speed forwards without as much spin causes the disc to go to the right, but if you get proper snap which imparts more spin, you can throw the disc just as hard and it will resist that right turn. Which is opposite to what you are saying.

 

[sumo21]

It all depends on the particular disc how much spin is on it. Simon Lizotte can throw a p2 which is a slightly more stable putter 400' and it won't turn over. Some discs are much more speed sensitive. Let's say we are talking about a Valkyrie. If you throw certain Valks with 200' of power they will hyzer out early, 250' of power they will hold flat then hyzer out, 300' you might get a little turn, and at 350' you would have to start it with some hyzer to avoid it turning all the way over.



Spin doesn't contribute to speed, but spin will keep the disc on the axis it is spinning on longer. E.g. more spin would make a disc thrown 200' stay on whatever axis it was released on until it hit the dirt. Then it would probably be spinning so fast it would light the grass on fire and the disc would melt

Not to say you shouldn't pursue these questions, but talking about speed vs spin is interesting more in theory than in practice. If you work on good form and getting a clean release you will generate enough spin and speed without "trying" to spin the disc.

CW: clockwise
HST: High speed turn
LST: Low speed turn

For the RHBH, that CW spin is what can make it turnover or stay straight or hyzer out. The faster, the more CW revolutions, the more likely the disc will want to start turning over, HST portion of flight. That is neglecting the aerodynamics, weight and other factors the disc. When the disc starts to slow down, LST portion of the flight, the less likely the disc will want to turn left and eventually fading at the end.

 

[mashnut]

CW: clockwise
HST: High speed turn
LST: Low speed turn

For the RHBH, that CW spin is what can make it turnover or stay straight or hyzer out. The faster, the more CW revolutions, the more likely the disc will want to start turning over, HST portion of flight. That is neglecting the aerodynamics, weight and other factors the disc. When the disc starts to slow down, LST portion of the flight, the less likely the disc will want to turn left and eventually fading at the end.

If I'm understanding what you're saying, I disagree. High speed turn is decreased when the disc is spinning faster, not increased. That's why someone like Barry Schultz can throw a 400' hyzer with a leopard where most of the rest of us can't get anywhere near that distance without turning the disc over.

 

[Annakin SkyHyzer]

^ This

 

[loki the trickster]

If I'm understanding what you're saying, I disagree. High speed turn is decreased when the disc is spinning faster, not increased. That's why someone like Barry Schultz can throw a 400' hyzer with a leopard where most of the rest of us can't get anywhere near that distance without turning the disc over.

Its about letting the aerodynamics of the disc fighting itself. a disc when it slows down wants to go left. So for a RHBH but the more aerodynamic a disc is like a leopard or road runner will create lift on its leading edge (the part of the disc opposite of your hand) beacuse it is traveling faster then the non leading edge. Therefore the more lift the more understable a will tend to be. The spin and aerodynamics of a disc will become apparent with a head wind. A less stable disc like a leopard will act as if the disc is overpowered and have more lift, while In a tail wind a leopard will have less lift cause the non leading edge will have lift cause the directon of spin will be spinning into the wind.

I hope this is not that confusing. also this is just my opinion and i dont hold any physics degrees.

 

[BogeyNoMore]

Heed the words of the Super Moderator, for he is wise and speaketh the truth.



















I'm being totally serious. Every word he said is spot on.

 

[pillbug]

As a noob DGer and an old timer amateur physics nerd, I've researched this for a while now, and everything I've read physics/math-wise so far agrees with sumo21 et. al.

The paper at http://www.odgc.ca/files/dg-flightphysics-mkIV.pdf gives a pretty good non-math overview of two of the 'sideways' forces involved due to spin (page 3 & pages 5-6).

That's why someone like Barry Schultz can throw a 400' hyzer with a leopard where most of the rest of us can't get anywhere near that distance without turning the disc over.

Could this be due to his relatively high ratio of spin speed vs air speed compared to 'the rest of us' (excluding myself since I'm a noodle arm noob), causing the spin-induced sideways forces to pretty much cancel each other out?

And for someone whose spin speed vs air speed ratio is lower, to the point where the air speed asymmetric lift force (what wims was referring to) greatly exceeds the gyroscopic precessional force, the disc flips?

Just curious how the physics/math can be matched up with the empirical evidence because I'm wanting to eventually code up a realistic DG simulator.

 

[Timeetyo]

I keep reading that, but the aviation enthusiast in me is a bit puzzled about it. I would think that the spin creates increased airspeed over the left side of the disc compared to the right side of the disc. This increase in airspeed should lift the left side causing the disc to turn. Once the disc loses speed and spin the air friction of the disc spinning will overcome the lift forces causing the wing to lift and the disc starts to fade

Exactly what makes the disc fly more stable when it spins?

"stable" is a dangerous term here as it has various meanings on here. If you dig around the forums here you will find a few really long nerdy threads where this is hashed out, but hopefully this helps:

1 - The difference in lift from one side of the disc to the other is negligible at best and isn't the reason that spin is so important to stability.
2 - Spin does the following 2 very important things to our discs in flight:
2A - Spin gives the disc resistance to change it's angle (hyzer/anny, etc). Same reason a toy motorcycle with a spinning weight stays up - that mass wants to continue rotating on the same axis. This means a disc with more spin is more likely to hold whatever angle it is currently on for longer (see mashnut's post below). It isn't necessarily that the disc is suddenly more stable (teebird vs firebird type stable) - it is that a disc with much more spin wants to hold its angle longer. So in addition to being able to get a leopard out longer - that is also why you can see someone with a ton of spin get a disc to hold an Anny line to the ground even when it has slowed down considerably. The spin makes it want to hold that angle....until another force is greater.....
2B - Gyroscopic Procession (spelling is likely wrong) makes our discs turn & fade as the center of lift changes. Do a search for a better description, but basically for a spinning object the force applied to the disc gets translated 90* in the direction of the spin. If your center of lift is in the back of the disc (relative to the center axis), there is a lifting on the back, which translates to an actual lift of the left hand side of the disc (or turn) for RHBH. This is force fighting the discs desire to hold its angle from 2A. If the center of lift is in the center of the disc....it is neutral. If the center of lift is in the front of the disc, the force is on the front, which is translated to the right side of the disc (fade). For our discs, the center of lift is furthest back when they are going faster and moves forward as they slow. To what degree and where all depend on many factors such as the specific mold, nose angle, etc. Discs that are NOT very speed sensitive (will fly true at a wide variety of speeds (think teebird) are very neutral for much of the flight - their center of lift remains fairly central for a wide speed range. But a valkyrie, for example, is much more dynamic which is why you see a lot of turn then a decent fade.

If I'm understanding what you're saying, I disagree. High speed turn is decreased when the disc is spinning faster, not increased. That's why someone like Barry Schultz can throw a 400' hyzer with a leopard where most of the rest of us can't get anywhere near that distance without turning the disc over.

 

[ToddL]

^Timeetyo is pretty much 100% correct in his post.

Roll is generated by the location of center of lift combined with gyroscopic precession. At high speeds and low angles of attack, the center of lift moves backward, behind the center of the disc. The gyroscope will move that force 90degrees in the direction of spin and roll the disc to the right (RHBH, clockwise spin). At lower speeds and higher angles of attack, the center of lift moves forward, ahead of the center of the disc. The gyroscope will move the force 90deg in the direction of spin and roll the disc to the left.

If the disc is spinning fast, it will be more resistant to the roll force and will change it's direction a little slower.

I keep reading that, but the aviation enthusiast in me is a bit puzzled about it. I would think that the spin creates increased airspeed over the left side of the disc compared to the right side of the disc. This increase in airspeed should lift the left side causing the disc to turn. Once the disc loses speed and spin the air friction of the disc spinning will overcome the lift forces causing the wing to lift and the disc starts to fade

Exactly what makes the disc fly more stable when it spins?

A disc is not a helicopter. They don't exhibit the same aerodynamic characteristics. In a helicopter, the advancing blade sees the aircraft forward speed plus the blade's rotational speed. The retreating blade sees the aircraft forward speed minus the blade's rotational speed. If the helicopter is traveling forward at 100mph and the tip of the blade is moving 400mph as it's spinning, the advancing blade will see the air at 500mph whereas the retreating blade will see the air at 300mph. The faster blade will generate more lift, causing an unbalanced lift distribution over the rotor. (Helicopters will change the angle of attack of the blade as it's spinning to balance out the lift distribution.)

Discs don't work like that. The disc is a solid body, and the entire body sees the air at the same speed. The left side of the disc is traveling 50mph, the right side of the disc is traveling at 50mph.
The only nuance here would be frictional effects. The "advancing" half of the disc would have more friction with the air than the "retreating" half, so the lift on the advancing side would be ever so slightly less than on the retreating side. This is opposite of how a helicopter sees it, but the effect is utterly negligible.

As a noob DGer and an old timer amateur physics nerd, I've researched this for a while now, and everything I've read physics/math-wise so far agrees with sumo21 et. al.

The paper at http://www.odgc.ca/files/dg-flightphysics-mkIV.pdf gives a pretty good non-math overview of two of the 'sideways' forces involved due to spin (page 3 & pages 5-6).

That dude is almost 100% wrong about everything. His explanation of page 5-6 is making the helicopter mistake. (And even if the helicopter assumption were true, you'd still have to account for the precession of that force. The difference in speed of the advancing/retreating blade manifests itself as a pitch (nose up/down) moment, not a roll moment.)