discspeed wrote: JHern wrote:
plex wrote:...Im not sure why you wouldn't throw such superior discs, with superior gyroscopic properties that hold lines longer, and glide farther than anything else i have ever thrown...
I like MVP discs, but I must chime in and say that the "superior gyroscopic properties" is just a gimmick, and it has never been backed up...
I understand skepticism is essential to any sort of scientific reasoning, and your math/science background is far beyond my reach, but I still think it's reaching a bit far to simply call it a gimmick...
It is a hypothesis that I've tested, and that I've found to be lacking.
discspeed wrote:It would be absolutely retarded of MVP to incur double the production costs to double mold their discs for a gimmick.
Maybe so, but perhaps there are other good reasons for molding the plastic this way, and they just got lucky that it flies well, and then mistakenly called it "superior gyroscopic blah blah..." For example, they could not use the smooth rigid clear plastic in the flight plate for the entire disc, it would be too slick to get a firm grip. They also could not use the outer black rubbery stuff for the entire disc, either, but it makes for a great rim feel and much improved grip. With both pieces, I think it makes for a superior disc that is much stronger, resistant to impacts, will last a lot longer, beat-in more slowly, etc..
I think the double mold is a great idea, but I'd be very surprised if they were originally motivated to do this for the purpose of increasing the moment of inertia...all they have to do is estimate the magnitude of this effect on the back of an envelope, and they'd see that at best there can only be a very slight gain. And then they can perform another estimate of how this will affect the flight. It would be unwise to NOT do these steps before engaging in an expensive production technique.
discspeed wrote:...I believe you are missing something(Chad could probably talk it out with you, but he's unlikely to get into proprietary info on the net). If not, then almost all my experience throwing discs is useless because MVP discs fly different for me than similarly shaped single plastic discs do.
The only thing proprietary about their process is the double molding, and I do think that's pretty cool!
The thing about discs, and we all know this very well from experience, is that a teensy, tiny, microscopic, imperceptibly slight variation in the disc shape can result in dramatically different flight characteristics. The difference in thermal expansivity between different plastic runs causes the disc to shrink differently out of the injection mold. Thermal expansivity is a very small effect, roughly of order several microns in disc diameter for every degree celsius cooling...for a typical disc, it probably shrinks by of order a few hundred microns. But in comparing different plastic blends, only the difference in thermal expansivity matters, so you're really just comparing tens of microns changes in shape between one blend and another. But changes of order ten microns (a dust particle this size cannot be seen by the naked eye) has a HUGE influence on the flight characteristics of an injection-molded disc...as disc golfers, we know this from experience.
Why is the flight so very sensitive to microscopic changes in disc shape? In fact, we know the answer: It is because the flow of air induced around a disc in flight is highly turbulent and non-linear. Mathematically, we know that this comes from the velocity squared term in the governing equations (aka Navier-Stokes), a term that has also been called the "Reynolds stress." This term, balanced by the dynamic pressure gradient, dominates the aerodynamic force balance on a disc in flight. Viscous stresses and body forces (in the air) are not important at the scale length of the disc, they only become important at very small length scales (where eddies are dissipated and transformed into random thermal motion of air molecules). If you change the surface around which air flows, even slightly, the previous pattern of flow becomes unstable and it is significantly modified. This changes the pressure distribution around the disc surface, causing it to anhyzer or hyzer more or less, hold the line better, etc., and all of this is occurring in ways that are difficult to predict because the flow is turbulent. Note that aerodynamicists are still struggling to understand why dimples on a golf ball allow it to fly so much further...these are not easy problems to solve!
So, whenever I see something different in one disc vs another disc, my first instinct is to suspect that there is a subtle shape difference, and I know for a fact that imperceptible shape differences can affect flight dramatically. When I calculate the maximum possible moment of inertia that a disc can have, and I see very little gain in using more dense plastic on the rim, then it leads me to believe that a subtle difference in shape, probably correlated with the double molding process, is very likely the cause of differences in flight between, for example, the Ion vs the Wizard. And there are many good reasons to expect slight differences in shape between them, given the dramatically different molding processes and plastics they use. The aerodynamical influence of the seam between the 2 plastics might also be important in giving the Ion characteristics that differ from the Wizard.
In the end, all of this can be easily measured and tested...with the right instruments and facilities, I could actually produce a very precise diagnosis for any kind of disc, particularly in comparing different discs. If only I could find the extra time (it would eat into my disc golfing time, too!). I will do it, one day, still hoping that a disc manufacturer could help with the (minor) costs...they'd get a lot of great info out of it, in return! But I would refuse to make it proprietary, the information would benefit everyone, and help us understand our essential sporting equipment.