NERD ALERT!!

[whatXhappened243]

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....

 

[bobmcnelly]

Wow, thats a lot of info to take in.

 

[whatXhappened243]

Hah! I forgot to post the link....

http://morleyfielddgc.files.wordpress.com/2009/04/hummelthesis.pdf

 

[Disc Fiend]

That is some pretty cool info man, thanks for sharing.

 

[Kodachrome]

thank you so much. this is going to make at least part of my work day tomorrow a breeze.

 

[bfowler]

See, that's what I've been saying.

 

[kevdiv48]

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

 

[thrembo]

Get you a copy of this book, if you're into this sorta thing.

 

[Hoosierhodge]

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

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 ;-)

To the OP - good find, I'll have to read more of it later. Kudos to Ms. Hummel for the hard work.

Hodge

 

[HyzerUniBomber]

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)

That makes sense. Nose down backhands when I actually keep the nose down seem to cut through the first 100-200'.

Most of the energy imparted into the disc goes into the translational not angular velocity of the disc

Can somebody tell me what that means?

Increasing wrist snap doesn't do much for increasing energy to disc.

Good to know... but -

Instead the most power comes from shoulder abduction, increased torque and rotation is translated through the kinematic chain to the wrist snap

-that is just passed making my brain hurt. Shoulder abduction = shoulder movement?

If so, I think it's saying that the real power comes from the dynamic whip of your arm starting at the shouder out to the wrist?

Very interesting stuff. Inner nerd very impressed.

 

[Kodachrome]

some quick google work then lunch is over.

translational = moving in a straight line. aka, most of the energy expended goes to generating forward motion (forward velocity) and NOT rotation (angular velocity, measured in degrees per second, etc.) so speed is what is generated more than "snap". and that is what you should be trying for.

 

[kevdiv48]

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 ;-)

To the OP - good find, I'll have to read more of it later. Kudos to Ms. Hummel for the hard work.

Hodge

Good call, I've done some work testing engine air system components via FEA and CFD. I agree it would be cool to test discs that way, considering they are very easy to draw up in CAD.

 

[chain_ape7]

Thank you so much for posting this....just printed it out at work and will share with my son tonight.
Wow - ......

 

[jrawk]

I think it's saying that the real power comes from the dynamic whip of your arm starting at the shouder out to the wrist?

I did not open the report. but "MOST" power from the shoulder is accurate. I know I'd be hard pressed to get anything past 100ft using only wrist.

But... when wrist is added to the throw properly large distance gains will follow.

 

[HyzerUniBomber]

I did not open the report. but "MOST" power from the shoulder is accurate. I know I'd be hard pressed to get anything past 100ft using only wrist.

But... when wrist is added to the throw properly large distance gains will follow.

You should open the report - it's interesting and basically says ... To paraphrase (it won't let me copy for some reason) -

throwers are often instructed on increasing wrist snap, but anaylsis suggests otherwise. At release, the power and work done at the wrist are on 8 @ and 0.2 J respectively while the main components of power and work occur at the shoulder from horizontal abduction (35 J) and joints (34J).

This implies that novice throwers might experience larger improvements by instead concentrating on increasing the power at the shoulder by increasing the horizontal abduction rate. This increase in torque and angular velocity may translate to the wrist. While wrist snap, may be important for imparting max anglular velocity to the disc, it's possibly of secondary importance to translational velocity for the beginning thrower.

So ultimately if you can generate 79 J from a good shoulder whip with NO wrist snap - adding another 8 from wrist could be extrapolated to adding 10%.

 

[notroman]

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

https://www.dgcoursereview.com/dgr/forums/viewtopic.php?f=17&t=14825

Another chart that I found very informative was generated by a computer that shows approximate [overstable] disc flight when released on various hyzer angles from -5 degrees (hyzer) to +5 degrees (anhyzer) in 1 degree increments. This just proves the theory that hyzers are a more consistent shot - notice how a disc released on a hyzer angle can be off by a degree and land within 10 feet or so of intended landing zone. A disc released on an anhyzer angle that is off by a degree will land much farther away from the intended landing zone.

 

[Rocaholic74]

This is a great thread....makes a lot of sense. I'm going to try and incorporate this into my form.

 

[HyzerUniBomber]

Notroman, thank you!!! Awesome chart.

 

[sidewinder22]

some quick google work then lunch is over.

translational = moving in a straight line. aka, most of the energy expended goes to generating forward motion (forward velocity) and NOT rotation (angular velocity, measured in degrees per second, etc.) so speed is what is generated more than "snap". and that is what you should be trying for.

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

 

[sidewinder22]

-that is just passed making my brain hurt. Shoulder abduction = shoulder movement?

If so, I think it's saying that the real power comes from the dynamic whip of your arm starting at the shouder out to the wrist?

Very interesting stuff. Inner nerd very impressed.

The right pec and closer shoulder drills are essentially teaching shoulder abduction since the elbow is forward, and the upper arm is not hugging/pinned against the body, so the arm can release/whip forward.