5 ms·

If by vertical you mean that the frisbee has rotated so the disc is perpendicular to the ground, that effect is actually aerodynamic, not gyroscopic. It comes f

If by vertical you mean that the frisbee has rotated so the disc is perpendicular to the ground, that effect is actually aerodynamic, not gyroscopic. It comes from imbalance of lift due to two halves of the disc see different relative airspeeds. In competitive disc sports this is usually mitigated by adding more spin (to add more moment of inertia in the spin axis to gyroscopically resist the turn), and by releasing the disc with the advancing edge pointed down to extend the period before it over rotates. If this is what you were talking about, then you should be able to just make the disc more edge heavy to try to counter act that. Or maybe you can try to someone add more drag to the forward spinning edge. Presumably if you have a single fin, that fin will usually be at the 6 o'clock position (from top view). Assuming we have a forward moving disc rotating clock wise (from top view), and the fin is at 6 oclock, then the forward rotating edge would be at 9 oclock. If you had a second fin (or some other type of feature) basically mounted at 9 oclock (so at 90 degrees relative to your main steering fin), then it should always spoil that air... might be able to use that to somewhat counter act the rotation. However, if you were actually talking about the gyroscopic effect (trying to rotate a spinning disc along it's axis pointing in the forward direction should cause a torque in its pitch axis)... I don't really know how to deal with that.

londons_explore 5y ago
I was talking about the fact that the center of lift is ahead of the center of mass of a circularly symmetric wing with positive lift. [1] That force would normally cause an aircraft to 'pitch up' (and hence planes have tail's and carefully balanced weight to stop this happening). In a frisbee, the gyroscopic effect means that this 'pitch up' force actually translates into a 'roll right' motion. By making the rim heavier, you can make this happen slower, but as far as I can see, you can never eliminate it entirely. My fin is on the outer edge of the disc, spinning with it, so it can oscillate at ~50Hz to get independant roll and pitch control, while also being able to trade off loss of angular momentum vs lift. It also has the benefit that it can be made from cardboard in a single pressing with the disc with no glue or assembly labor. [1]: http://ffden-2.phys.uaf.edu/645fall2003_web.dir/Mike_Abrams/Lift.h3.jpg http://ffden-2.phys.uaf.edu/645fall2003_web.dir/Mike_Abrams/...
- icegreentea2 5y ago
  Ah hm. I wonder which one of our two effects is dominant. I can see that your explanation must plainly exist - it's just not part of the standard "intuitive" model taught to frisbee players. That's a really clever fin design. If the dominant component of rotation was due to the center of pressure being ahead of the center of mass, could you to use timing of the fin being in a "high drag" configuration to pull the time averaged center of pressure back towards to the center of mass?
  - londons_explore 5y ago
    > could you to use timing [...] back towards to the center of mass? Yes, but sadly the effect isn't large enough until you end up with a very large fin and a very powerful actuator to move it. That difficulty is what made me put the project on the backburner for now.

londons_explore 5y ago

I was talking about the fact that the center of lift is ahead of the center of mass of a circularly symmetric wing with positive lift. [1] That force would normally cause an aircraft to 'pitch up' (and hence planes have tail's and carefully balanced weight to stop this happening). In a frisbee, the gyroscopic effect means that this 'pitch up' force actually translates into a 'roll right' motion. By making the rim heavier, you can make this happen slower, but as far as I can see, you can never eliminate it entirely. My fin is on the outer edge of the disc, spinning with it, so it can oscillate at ~50Hz to get independant roll and pitch control, while also being able to trade off loss of angular momentum vs lift. It also has the benefit that it can be made from cardboard in a single pressing with the disc with no glue or assembly labor. [1]: http://ffden-2.phys.uaf.edu/645fall2003_web.dir/Mike_Abrams/Lift.h3.jpg http://ffden-2.phys.uaf.edu/645fall2003_web.dir/Mike_Abrams/...

icegreentea2 5y ago
Ah hm. I wonder which one of our two effects is dominant. I can see that your explanation must plainly exist - it's just not part of the standard "intuitive" model taught to frisbee players. That's a really clever fin design. If the dominant component of rotation was due to the center of pressure being ahead of the center of mass, could you to use timing of the fin being in a "high drag" configuration to pull the time averaged center of pressure back towards to the center of mass?
- londons_explore 5y ago
  > could you to use timing [...] back towards to the center of mass? Yes, but sadly the effect isn't large enough until you end up with a very large fin and a very powerful actuator to move it. That difficulty is what made me put the project on the backburner for now.