Speed ratings and what determines them?

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Re: Speed ratings and what determines them?

Postby JHern » Thu Dec 31, 2009 8:41 am

Steady 26542 wrote:Great chart! Now I want to get a speed gun to know what speed discs I SHOULD be throwing... :mrgreen:

Would you say that someone that throws an OLF with just enough power for the disc to reach its idealized flight speed should be looking at speed 10 discs or less?

You're fine if the disc is performing the flight path it is designed to execute...e.g., if you're throwing a Boss but you can't make it turn at the highest speeds you can muster, then it is probably too fast and you should use something slower.

As a general rule I tend to only use discs that will turn for me (even if only slightly), although I will also keep discs in my bag that won't turn much at all...discs for flex shots, days with more than usual OAT or headwinds, and also something to grow into as my power improves. Right now I fall into about pwr=4-4.5 category on the flight chart, and I carry some pwr=5 discs in my bag (e.g., Valkyrie, Wraith, Destroyer, Orc) which are either under-stable enough or beat-up enough to turn for me (Valkyrie, Pro Destroyer) or fly stably for me in all cases even when I huck it as hard as I can muster (Star Domey Wraith, new Champ Orc).
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Re: Speed ratings and what determines them?

Postby flyzguy » Mon Apr 14, 2014 2:48 am

JHern wrote:A high speed disc cuts through the air more efficiently and it is harder for the air to "grab" it. This means it is more difficult for the air to slow it down, but it also means that it is more difficult for the air to make it turn or do anything other than fade out...cutting drag also means cutting turn at a given speed. I.e., the disc's ability to turn or hold a line depends on its ability to interact with the air. If the disc has low drag, then you have to throw it faster in order for the disc to "feel" the air. At a high enough speed (which is different for every mold) the air can "grab" the disc and make it turn or perform whatever kind of aerobatics the thrower desires.

Nothing personal JHern, but for the sake of aerodynamics folks everywhere I have to say this explanation is really really wrong. Discs turn because the center of pressure is not on the center of gravity - creating pitching and rolling moments. Because our discs spin, these moments (or torques) cause the disc to react like a gyroscope, which can be non-intuitive. Everything gets "delayed" by 1/4 of a spin - so a "nose up" becomes a "turn left" and a "nose down" becomes a "turn right" (RHBH). For example, when your driver rolls left (RHBH), it is because the air is pushing up on its Nose. This is almost certainly the center of pressure moving forward of the CG on the disc as the angle of attack increases. Most of this force is from lift, not drag so much. The shape of the nose and the flightplate dictate how the center of pressure moves along the disc during different phases of flight. Manufacturers can and have made very slippery low drag discs (what you would call high speed) that are understable.

So drag and turning characteristics absolutely do not go together the way you say they do. We can have draggy stable and slippery understable (and we do).
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Re: Speed ratings and what determines them?

Postby JR » Tue Apr 15, 2014 1:57 pm

Welcome the the site. Think about how inaccurate the speed ratings are. innova has a bunch of guys throw the disc and a number is slapped on the disc. So much for drag coefficients.
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