NERD ALERT!!

[Kodachrome]

Yep, spin is more a byproduct of speed. "Always work on speed rather than spin." - Climo "Throwing a disc is different than spinning a disc." - Avery

That is funny; I really have never seen those quotes before. It's fun taking concepts and quantifying them like this.

 

[EWSdiscgolf]

That's a lot of info to take in. Very impressed with your awesomeness. I wouldn't call you a nerd.
What's your player rating? Post the answer on my page.

 

[Nemmers]

So the distance vs disc speed thread got me thinking... If there is this kind of info out there, what other studies have been done in regards to the aerodynamics of disc golf and frisbees. Well, a little internet searching turned up some interesting reading... As part of a master's thesis for mechanical engineering, Sarah Hummel (possibly my future wife, but thats another thread...) introduces a detailed explanation on frisbee flight.

Some of the info can be a little difficult without a background in engineering or physics and anatomy and physiology, but it is insightful nonetheless. (Wikipedia should be useful to fill in the gaps if needed). I will point out some of the noteworthy segments:

• Sect 2.2.3:
  
  Drag force is minimum when lift is zero. This happens when angle of attack is about -4deg. (The disc's nose is turned downward 4deg with respect to the direction of flight)​
• Sect 2.2.6
  
  The lift force would make sense to be greater to the left of the midline than to the right, so discs should have a positive roll moment and turnover naturally. Not the case, explaining why they fade out at the end.​
• Sect 2.2.6, 2.3
  
  At low spin rates, the left-to-right force is negligible, so they are neglected from the EoM. Spin plays a bigger factor in providing stability during flight (makes sense)​
• Sect. 2.3.2
  
  OAT is caused by angular velocities introduced about the x- and y-axes.​
  
  
  OAT dampens during the throw, bc disc throws are not torque free motion. The torque is caused by the COP not being coincident with the COM.​
  
  
  Positive roll moment causes the nose to dive. (Turnover shots typically finish nose down) Negative roll moments cause the nose to lift. (hyzers flare up)​
• Sect 2.4.2
  
  Nose down flight with positive angle of attack gives flight with where lift force equals gravity.​
• Sect 2.4.3
  
  The fade at the end of the discs flight is caused by the increase in pitching moment during flight. This increase is caused by the decrease in velocity caused by drag and gravity.​
• Sect 2.5
  
  Disc design to produce desired flight....​
• Chap.3
  
  Mathematical models to produce data for frisbee flights​
• Sect 4.1-4.3
  
  Modeling the body during backhand throw. (Blah, blah, blah...)​
• Sect 4.4.1-4.4.2
  
  Body motion troughout the throw.​
• Sect 4.4.3
  
  All your power comes from the body, not your arm (Work on your form!!!). Most of the energy comes right before, not at the release of the disc.​
  
  
  Most of the energy imparted into the disc goes into the translational not angular velocity of the disc​
• Sect 4.5 (Specifiically 2nd paragraph)
  
  Increasing wrist snap doesn't do much for increasing energy to disc. Instead the most power comes from shoulder abduction, increased torque and rotation is translated through the kinematic chain to the wrist snap.​

If only the idea for my thesis didn't just get thrown out the window....

I love lamp.

 

[whatXhappened243]

Thanks for sharing! I'm an ME undergrad myself, so I'm excited to see how much of this I can actually understand.

I think you'll do alright. As long as you've taken basic fluid mechanics, and dynamics you should be able to get a good grasp on the info. I didnt see anything beyond the scope of those classes in there. PM if I can help with anything, I'm a ME EIT so I am happy to help

Take a CFD class if you get a chance and maybe you can do some disc modeling as a project. You could do something cool like analyze several disc profiles to better understand why some are stable/overstable/understable and then make up your own! I do structural dynamics/FEA analysis for my job rather than CFD but CFD is good for some stuff like disc golf and airplanes ;-)

I did a few experiments on airfoils for my ME Lab class last year... I wish I would have focused on something like this for our design of experiment project instead of jet stream force analysis. (got out-voted by my group)

That's a lot of info to take in. Very impressed with your awesomeness. I wouldn't call you a nerd.
What's your player rating? Post the answer on my page.

Yeah, it was a good 2hrs of very focused reading when I first cane across the paper. And the reason I gave the thread this title was cuz for one: I actually read it all the way through, two: I got a good grasp on all the info presented, and three: the mrs was quick to drop the "NERD!" bomb on me

Im not sure of my player rating, most of the tourneys I've played in have all been minis, so no ratings were ever posted (to my knowledge). I did play one doubles round in the Live Oak summer Open a few years back, placed 2nd, but never followed up for more info after that. I usually average 3 down at most of the local course in San Antonio.

 

[HyzerUniBomber]

So I was having a long "nerd talk" with my brother over the weekend - and I was talking about some of the stuff that came up in this thread... trying to put it together into something that makes sense to a non-physics guy.

Does this make sense?

You give up the larger moment of inertia by going with a lighter disc, but you have to impart less acceleration to get the same force. So at some point, a guy like Paul McBeth can throw 165-170 drivers (instead of 175) - and make up the difference lost in the disc spinning longer by being able to spin it easier.

The biggest thing I'm noticing from this discussion is that we're delaying fade and turn by increasing spin. While I'm trying to throw further than 400' - it seems like my biggest focus should be increasing spin which comes from a combo of acceleration and whip motion.

 

[iacas]

You give up the larger moment of inertia by going with a lighter disc, but you have to impart less acceleration to get the same force.

The gist of what you're saying is right, but don't mix up things like F=ma.

The force in that situation is muscular force that accelerates your arm (and the disc). You can find out how much force was needed if you can measure the acceleration of all of the parts, but since it's well beyond a simple linear motion, you'd be hard pressed to do that accurately.

F=ma explains why the same person with the same amount of effort ("force") will be able to accelerate his arm faster than the same person wearing a five-pound weight on his wrist. If "F" is held constant and "m" increases, "a" will decrease.

 

[HyzerUniBomber]

So I guess the next question is what is the real difference between 5-10 grams when it comes down to inverses and multipliers in terms of real world #s?

Is it really something you can feel? I personally can't feel any difference in a 175 and 170 driver, probably because the acceleration and release happen fast.

 

[iacas]

So I guess the next question is what is the real difference between 5-10 grams when it comes down to inverses and multipliers in terms of real world #s?

Is it really something you can feel? I personally can't feel any difference in a 175 and 170 driver, probably because the acceleration and release happen fast.

I could answer this both ways. So here goes:

No, because as a percentage of your whole arm, even 10 grams is a tiny difference given how your arm weighs several kilograms by itself.

Yes, because the weight is farthest out, it affects SPIN as well as linear velocity, and because your fingertips are the most sensitive so added weight can affect the consistency and "feel" of the angle on which you're throwing the disc as well. Plus lighter discs glide a bit better, all else equal, so these little things can add up to noticeable amounts more distance for lighter discs.

 

[notroman]

Yep, weight definitely affects how much spin you can impart on a disc. Try those gripper exercises made specifically for fingertips (as opposed to hands) and you'll find that even 5lbs of pressure takes a decent amount of power to exert, more than most people do when they're holding on to a disc. A lot of people have the disc slip out way early.

 

[knettles]

I think you'll do alright. As long as you've taken basic fluid mechanics, and dynamics you should be able to get a good grasp on the info. I didnt see anything beyond the scope of those classes in there. PM if I can help with anything, I'm a ME EIT so I am happy to help



I did a few experiments on airfoils for my ME Lab class last year... I wish I would have focused on something like this for our design of experiment project instead of jet stream force analysis. (got out-voted by my group)



Yeah, it was a good 2hrs of very focused reading when I first cane across the paper. And the reason I gave the thread this title was cuz for one: I actually read it all the way through, two: I got a good grasp on all the info presented, and three: the mrs was quick to drop the "NERD!" bomb on me

Im not sure of my player rating, most of the tourneys I've played in have all been minis, so no ratings were ever posted (to my knowledge). I did play one doubles round in the Live Oak summer Open a few years back, placed 2nd, but never followed up for more info after that. I usually average 3 down at most of the local course in San Antonio.

Good god. I'm not embarassed to say I think that was the hardest class I will ever take in my life. And I like physics. And am decent at it.

 

[HyzerUniBomber]

Thanks guys, I sincerely appreciate the input. I know that ultimately KNOWING and DOING are 2 completely different things and I'm sure there's quite a few pros that haven't the foggiest as to what the physics are of what they're doing. But I enjoy the technical side of it as well and when a disc is gyro-flying across a field I sometimes feel like I can see the little vector lines pushing and pulling on it.

 

[tampora]

This is the thread/information you are looking for (this will also explain why discs fade in a certain direction relative to their spin).

What equation generated this?

 

[notroman]

What equation generated this?

I solve F=m*a=m*dv/dt and rxF=d(I*w)/dt (conservation of linear and angular momentum, respectively) where F is the aerodynamical force, m is disc mass, a is disc acceleration, v is disc velocity, t is time, r is the aerodynamical moment arm, I is the moment of inertia, and w is the angular velocity (spin). The numerical solution method is Runge-Kutta, 4th order. This throw is for a m=175g disc, thrown at 4 Hz rotation (which dissipates with time during the throw), 65 MPH release speed, no wind.

Actual FB post if the permissions allow you to see it: Chart

 

[theeterrbear]

Plus lighter discs glide a bit better, all else equal, so these little things can add up to noticeable amounts more distance for lighter discs.

But at the same time a heavier disc will cut through the air better because drag will have less of an effect on the disc. Food for thought.

To make it more accurate, it really boils down to whether the two discs are actually thrown with the same amount of force and how the energy is "spread" out. Will the lighter disc have more rotational energy or a higher velocity? Will one disc be thrown consistently with more force than the other, because we're humans and we do that?

Now I gotta read that paper.

 

[HyzerUniBomber]

But at the same time a heavier disc will cut through the air better because drag will have less of an effect on the disc. Food for thought.

To make it more accurate, it really boils down to whether the two discs are actually thrown with the same amount of force and how the energy is "spread" out. Will the lighter disc have more rotational energy or a higher velocity? Will one disc be thrown consistently with more force than the other, because we're humans and we do that?

Now I gotta read that paper.

I need to double check, but I'm pretty sure that drag is completely independent from mass.

 

[HyzerUniBomber]

Disc Drag: This is the aerodynamic drag on the disc due to its displacement of the surrounding air, and tends to decrease the speed of the disc in flight. Disc flight is typically in the turbulent flow regime, so that the drag is proportional to the square of the disc speed. The rule of thumb is: if you throw the disc with twice the speed, you get four times the aerodynamic drag.

Drag force is a function of the shape of the disc, nose angle, and speed alone. Drag force is completely independent of the disc mass. The drag typically increases in proportion to its cross-sectional area projected along its flight trajectory. If the disc's nose angle changes, then so too will the cross-sectional area of the disc.

...That's from the dgr thread posted earlier in this thread.

 

[mashnut]

The drag force may be independent of the disc's mass, but acceleration (change in speed) is dependent on both force and mass.

 

[iacas]

The drag force may be independent of the disc's mass, but acceleration (change in speed) is dependent on both force and mass.

A disc doesn't really have "force." Forces act on things, so if your disc hits a wall, yes, you can measure the force with which the disc hits the wall. While it's moving, it makes more sense to think of it as having energy because it's moving (and it's in the air) and to consider the "force" as what's put "into" the disc to get it moving.

Again, if F=ma for throwing a disc, and you have two discs of mass X and Y (with Y being higher than X), and the same "throw" (i.e. the same F and the same time), then the Y disc will be accelerated more slowly than the X disc and will launch with a lower initial speed.

Then you get into Kinetic Energy equations, where K=1/2 mv^2 - notice that the velocity is squared in this case while the mass is simply a multiplier. A 20% increase in mass increases the K by 20% while a 20% increase in velocity bumps it by 44%.

But again, these numbers don't factor in the fact that a 10g difference in disc weight is really small compared to the weight of even your arm.