Tuesday, July 23, 2013

gyroscopic forces having to do with angular momentum

Current DGCR Rating - 726 Up from 722


The good news is I had my first 2 birdie round. The bad news is I lost my first disc In said round.

I played Crystal Lake Monday and had a 56 which is a rating of 751.  It's tough to tell how good you did since all holes are par 3s for the sake of simplicity.  But courses as a whole are rated.

Anyway I simplified my forehand to a single step and had good results. My first birdie was a 208 foot shot that came up a little shot and I tossed in a 15 foot birdie.  Then the 2nd birdie was a short but pin bally 160 footer.  The tricky thing on this is that the basket has trees in front of it and a marsh land on the right side.  It's guarder on the left by trees.

So you have to throw the disc over the marsh and as the spin slows you HOPE it fades towards the basket.   I threw it and . . oh no, not that far over the marsh but it glides back and lands 3 feet from the basket.  Perfect!!   a Gimmie birdie!!

Almost had one more on a 182 foot shot that has to bend around some trees but my 35 foot putt hit the side of the chains but didn't stick.

Of course I was still thinking about THAT shot and basically through my disc into the ground on the next uphill shot.

There is a pretty good explanation on  how a disc works that I'll sort of repeat here. 

Originally posted by LoPan12

   When the disc flies through the air, you get a distinct seperation of air flow. Now consider two particles that get split up be the disc, one goes on top, one goes on the bottom. They will meet up again, behind the disc, so, because the top one has to travel farther, it is going faster. As speed increases, pressure decreases. You are left with a lower pressure area above the disc, and a higher pressure area below the disc. This phenomenon is called "LIFT" and for a given speed, will overcome the weight of the disc, and push it up. 

When you now consider the rotation, think about relative speeds. For a RHBH, the left edge of the disc is moving faster than the right edge. So, due to the higher speed, the left edge will create MORE LIFT than the right side.  

So why don't all my discs keep going right?

Well...you've got a rotating mass. This causes gyroscopic forces having to do with angular momentum and pitch and roll and whatnot. In a nutshell, the rotating mass of the disc causes a sum of forces call gyroscopic procession. This is what causes LSS (Low speed spin), same as HSS(High Speed Spin), just the opposite direction.

When you first release the disc, it has the most spin it ever will in that flight, and the assymetrical lift forces will outweigh precessional roll. But as the disc slows down, the lift forces aren't as large, and the disc rolls to the left. 

It slows down, because of DRAG! Drag is a force that opposes your disc. The friction between the disc and air rob energy and the spin reduces, and the forward speed declines! BTW, a driver has less drag than a putter, due to putters having a blunt edge. So a driver's flight is therefore less lift-driven, and more ballistic. But don't think about that for now.

NOW, those of you still reading (god-bless you) are asking, "Okay, neat...what's this shit have to do with beating in and more glide?"  (the question was why do older disc seem to get more glide).

Well, turbulence is our friend here. A turbulent boundary layer on the surfaces of the disc eventually result in less drag! There's more fluid dynamics involved here, but trust me when I say, you end up with less drag. This is why golf balls are dimpled, but the reasons are a bit different for a sphere.  

So, as you beat in a disc, it gets all these micro abrasions, that cause little eddies and vortexes that add up to turbulent, chaotic flow. In some cases, while this turbulence increases surface friction drag, the overall effect is a reduction in drag forces. This has to do with boundary layers, seperation points, and changes in pressure fields.

The beating in reduces drag (to a point, then you start to get screwed again) allowing a disc to maintain the various lift forces for longer, lettings it go longer before fading, letting it glide longer.  

AWESOME - this is why I love disc golf.

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