Nose down question.

[aDave]

Are we talking nose down relative to the forearm/palm or to the angle of ascent?
It seems to me that if it's relative to palm then as it rotates through the fulcrum you will get OAT?
Then again it seems to me that if it's relative to ascent angle then you are exposing the flight plane at release which according to
Blake (my unseen/met master) is a no no.
Seems then that it's relative to forearm and the wrist rotates with the nose down relative to that?
what do I not get?
I know what nose down looks like on a push putt. I am having some success with tweaking nose angle to get my disc to fly down into the chains (maybe not the best approach, but it's very satisfying when it works). But with a power/fork/what have you grip, my wrist just won't bend that way.
My form isn't perfect, but I can line drive 350 with an Orc with little to no fade and I've grazed 450 with a Valk on high apex lines on occasion so I think that I can get more with d with this.
Enlighten me please!

[Star Shark]

It's relative to the flight of the disc. You can get away with nose level but nose up and the wind gets under your disc and pushes it up into a stall/fadeout.

[aDave]

Gotcha. Now on to figure out how to do it.
It seems like it would be really difficult to achieve a clean release if your wrist angle is much off from the rest of your arm, so I can imagine that this is easier with hyzer or annie.
I've been trying to hit a high apex with a flat release.
is that where the stoopid lurks?

[Star Shark]

It's more difficult. The disc pivot often slings it into a more nose down position, but throwing high shots is quite difficult. Blake said some tiem ago on the forum to think of it as if you're trying to hit the ceiling of a room with the flight plate of the disc.

[Dookville]

I have been athletically inclined all my life and it has related to learning disc golf pretty well. But....throwing high nose down shots have been a bear. Blake puts things in such a way that it is really easy to understand, but I have been unable to find anything that he has written on the subject. In the meantime I have resorted to trying to imagine the throwing my final motion of lifting the tail of the disc like I do my putts right at the hit. Sometimes its magic, but most of the time I crash and burn

[aDave]

Got some advice from a local "better than me guy" today. His suggestion was to try messing around with wrist roll at release in order to get a feel for the plane at release. I did and I began to sort of get what he was talking about. we will see.
On another note he also noticed a timing issue in my form that was really illuminating.
Nothing like in person feedback!

[Dookville]

Got some advice from a local "better than me guy" today. His suggestion was to try messing around with wrist roll at release in order to get a feel for the plane at release. I did and I began to sort of get what he was talking about. we will see.
On another note he also noticed a timing issue in my form that was really illuminating.
Nothing like in person feedback!

Thats how I try and get the rear of the disc to come up, by rolling my wrist.

And....you are right, when you start adjusting things that late in the throwing motion you really start to notice things, pretty cool.

[Blake_T]

nose down is mainly determined by these 3 factors:
1. a pull line close to the body.
2. getting your weight forward.
3. wrist extension.

throwing high and nose down can be a PITA, but it can be developed easily in less than a week.

for those that aren't graced with enough velocity to generate insane lift, the easy answer to throwing higher = throw higher.

Blake said some tiem ago on the forum to think of it as if you're trying to hit the ceiling of a room with the flight plate of the disc.

this is correct.

the way to work up to things is to start with slow discs that have very narrow rims. e.g. putters.
pick trajectory points (read as: imaginary hoops) you want to pass through relatively close to the tee (e.g. 50' away) and try to throw through them. as you are able to get "decent" altitude on a nose down throw (e.g. 20' apex or higher), move up a step in speed and width, the next step being midranges. when you are able to get decent altitude, move up a step on speed and width, e.g. fairway drivers.

wide rimmed drivers may never happen because their required cruising speed in addition to the rim width makes it much more difficult to get them to hold nose down through the apex.

flat throws are the most difficult to throw high and nose down. it's much easier to hyzer flip (assisted with OAT) or anhyzers to learn to get the nose down on higher throws.

if you are throwing a distance tower the key is to have trajectory points both for the apex and a point beyond the apex and attempt to fly through both of them while having a particular disc orientation as it passes through each of them, with greater emphasis placed upon hitting the 2nd hoop after passing through the first one. i posted a craptacular photoshop picture of this a while ago. if you are having trouble visualizing wtf i'm saying, imagine shooting a basketball... with 2 hoops. one in the air that you want to pass through, and one that is the basket that "counts." your goal is to pass through both of them but it's most important that you make it into the second one.

[aDave]

Thanks Blake! I will drill.

[Blake_T]

i forgot to explain this: for those that aren't graced with enough velocity to generate insane lift, the easy answer to throwing higher = throw higher.

your body mechanics will naturally adjust if you simply attempt to throw higher, so focus more upon your intended flight line than anything your body is doing. what has to be done will naturally happen in order to perform the throw.

a disc rises naturally when you exceed it's cruising speed (it levels off when it slows down into its cruising speed).

when you throw upwards (without exceeding its cruising speed) you are fighting gravity and the disc will decelerate faster. if it slows down too much it will stall and fall. what this means is that how high you can throw a given disc with your given power is that you can throw a slower disc higher than a faster disc without stalling it out.

for someone who drives say 350', they should be able to perform a nose down putter throw with a 25-30' apex, a midrange throw with a 20-25' apex, fairway driver in the 15-20' apex, etc. it's common for people at that level to not be able to throw something like a destroyer or nuke over 12' high without stalling it unless they do some tricks with angles and OAT.

an easy drill for this is to find an obstacle of a given height between you and a target. practice throwing over the obstacle while parking the target.

[Sean40474]

That sounds like a fun drill Blake, I'll try this as soon as I can and report some results and observations.

[JHern]

an easy drill for this is to find an obstacle of a given height between you and a target. practice throwing over the obstacle while parking the target.

That's several of the holes at my home course.

Every disc has an angle of attack (angle of disc moving relative to air) for which the aerodynamic lift force is zero. For discs with positive camber, this angle of attack is negative (though only slightly, like 5 degrees nose down). If it is flying with this particular nose angle relative to level ground, the disc will rise and fall with the acceleration of gravity alone, just like a golf ball would do in the up-down sense of motion.

Don't take my word for it. Get one of your discs, and stick it out your car window sideways with your arm extended (but not while driving too fast, or near objects that may strike your arm in passing...in fact this works better if somebody else is driving, and you're in the passenger seat). Drive about 30 MPH. Now, change the nose angle of the disc up and down, and you'll notice how the disc pulls up or pushes down. The force you feel is the lift force minus gravity. You'll notice that the disc has a neutral weight (just its natural weight, as it would be if you weren't driving) at a given angle. That angle is slightly nose down, and is the "zero lift force angle of attack." It is often thought that this angle does not depend on speed, which is true only if the form of air flow around the disc is the same planform at all speeds (just faster, but same pattern of flow). I think this assumption may very well be wrong, but in any case, it is a first approximation.

To generate lift force that would balance gravity and maintain level flight requires a smaller angle of attack (less nose down) than for the zero lift value, so that lift can balance the weight of the disc. You can also feel this from sticking the disc out your car window. There is an angle where the disc is practically "weightless" and gravity is exactly balancing lift. This is the angle of the disc relative to the ground that will allow your disc to fly level (in calm wind conditions) while flying at the same speed as the car. Let's call this the "level flight nose angle." Unlike the "zero lift force angle of attack," the "level flight nose angle" varies with disc air speed (higher nose angle for slower speeds).

OK, so if you put the nose down relative to level ground more than the "level flight nose angle" for the speed you are generating, then the disc cannot maintain level flight and will burrow down into the ground. If you put the nose up higher, the disc will ascend, lose speed, and then level off in flight for conditions of higher nose angle and slower speed. The disc will then gently fall as the lift force tails off owing to drag.

If you throw with a nose down orientation that is at or further down from the "zero lift angle of attack," then the disc will fall toward the ground like a brick no matter how hard you throw it. So there exists an extreme nose down angle range of no return.

I don't remember the point I was going to make. But yeah, this is an important topic.

[jubuttib]

@JHern: Does the spin of the disc disturb the flow of air in a meaningful way, at least when it comes to the "zero lift force AoA"?

[JHern]

@JHern: Does the spin of the disc disturb the flow of air in a meaningful way, at least when it comes to the "zero lift force AoA"?

Spin doesn't seem to affect the aerodynamical forces or torques on the disc, at least for typical hand-generated spin rates. I'd guess that if you get the spin rate up to hundreds or thousands of Hz that something might change. A throwing machine or extreme wind tunnel testing would be needed to evaluate where it becomes important. A spinning axi-symmetric object like a golf disc doesn't generate any boundary layer dynamics by itself, because the surface is invariant as the disc spins. So the only way for spin to enter the dynamics is by modifying the boundary layer flow generated by the motion of the center of disc mass through the air. But the only way for the disc spin to couple to the air flowing around the disc is through the boundary layer that forms over the disc surface.

You can evaluate the forces acting through this boundary layer related to disc spin coupling to the air around it by noting that it takes roughly 20 seconds for the spin of the disc to decay by a factor of 1/e (the e-folding time scale). The axial moment of inertia of a 175 g disc of 10 cm radius is around 0.002 kg-m^2. For exponential decay of spin, the spin down moment will be the axial moment of inertia times the spin rate divided by the e-fold time scale for spin decay. This gives for the spin down moment a value of spin*0.002/20~spin*1e-4 N-m. So if you're throwing at 10 Hz spin rate, then the spin down moment is 1e-3 N-m (this is good for an order of magnitude estimate). Dividing by the disc radius gives roughly of order 1e-2 N for the force associated with spin coupling to the air around the disc. The drag force that dissipates the disc's linear momentum is the drag coefficient times disc planform area times disc velocity squared divided by 2. For a drag coefficient of 0.1, air density of 1.3 kg/m^3, disc area of 3*e-2 m^2 and air velocity of 10 m/s the drag force is around 0.2 N (roughly half a pound). This is ~20X larger than the forces associated with spin decay at 10 Hz spin.

So the forces causing the disc spin to slow, which are the same forces that couple disc spin to the air flowing around it, are already an order of magnitude smaller than the forces associated with aerodynamic drag acting of the disc's linear momentum for nominal throw parameters. According to this estimation, you'd have to spin the disc at 100 Hz in order to get comparable forces associated with spin and drag at an air speed of 10 m/s. At higher air speeds, this discrepancy increases even more.

But these forces also act in a different sense. The spin down forces act around the disc circumference, while the drag acts from the leading edge to trailing edge. So even if you can couple spin to the air around the disc, it can just result in swirling the air (twisting it slightly) which might not actually change its ability to exert drag (or lift) at all. This is because effects on the advancing side could very well cancel the effects on the retreating side, with no net change even if the forces are comparable.

Anyways, there are lots of good reasons to neglect spin from aerodynamical forcing.

[jubuttib]

Just what I wanted to know, thanks.