JHern wrote:Mark Ellis wrote:Change the plastic and you change the disc.
As plastic comes out of the mold it dries. As it dries it changes shape. The top may pop up or sink down which changes the nose angle of the disc. Even tiny changes in shape change how the disc flies. And a disc flies differently at different speeds and with different degrees of flutter, so a disc may be changed but not noticeable by you...
I have to make a clarification, and edited Marks' statement according to my understanding...discs are not made of epoxy (which dries), but rather they are made of thermoset plastics, with compositions derived from thermopolyurethane, polyethylene, etc. (vibram rubber is an exception). Therefore this should read (changes highlighted in bold):Change the plastic and you change the disc.
As plastic comes out of the mold it cools. As it cools it changes shape by shrinking. Shrinkage is non-uniform owing to the non-simple geometry of the disc. The top may pop up or sink down which changes the nose angle of the disc. Even tiny changes in shape change how the disc flies. And a disc flies differently at different speeds and with different degrees of flutter, so a disc may be changed but not noticeable by you.
Also, I completely disagree with this statement...Mark Ellis wrote:Plastic formulas are constantly tweaked by manufacturers and no one knows how the next formula will fly-until it is thrown. So sometimes certain trends are noticed: a particular mold comes out more of less stable in certain kinds of plastic, but this is only a general rule and no true certainty exists until YOU throw a disc and learn what it does.
It isn't true that you can't predict the shapes/properties of plastics processed by injection molding, there is an entire field of engineering that is devoted to exactly this task. Entire suites of industrial software have been written to do exactly this job. Disc manufacturers simply don't use it because they don't want to pay for it, and probably the market isn't anyways big enough to justify the expense.
Being a practical guy (and not a scientific guy), did JHern just agree with me?
Plastic pellets are heated until they melt with other types of plastic pellets similarly melted together til they all mix in a kind of plastic soup. Then that soup is spit into a mold where it dries ( er.. skrinks or becomes non-soupy and more solid-like). From soup to solid is where the change of shape happens. I may be omitting or massaging some technical terms.
Disc golf is such a tiny, tiny (really darn small) part of the plastic market that the big plastic manufacturers don't engineer plastics for discs. Rather disc companies try out different kinds of plastic ( which are themselves ever changing) then blend them with other kinds of fancy, high-tech, ever changing plastics hoping to make discs which the disc golf world will love. So if a company bought enough plastic pellets of one type to last for a year by the time they needed to reorder that exact plastic may no longer be on the market, replaced with the newest, greatest, improved stuff which may be better for a car bumper but not as good for a driver.
So when the disc manufacturer buys the newest order of pellet and then mixes it with 3 parts of X and 7 parts of Y and 2 parts of Q plus weighting and coloring agents, NO ONE knows how it will fly until it is thrown. Oh, by the way, the next run which happens to have the exact plastics and the exact formulas as the last won't be run under the same atmospheric conditions. So perhaps with enough time, money and effort software COULD be developed to predict performance. But since no one wants to spend megabucks for a disc it ain't gonna happen soon.