In the PDGA memo detailing the removal of the turbo putt from the approved list it mentions discs should have "radial symmetry". How does this effect the Aerobie� Epic�? It does not have "radial symmetry" but to me seems to have a lot of potential and should not be labeled as non-PDGA approved. Thoguhts.

My reaction after reading the agreement was get to work on removing the Epic as an approved disc too. Yay!

The document say that members who objected to the Turbo-Putt said discs should have radial symmetry. The TSC and Board said the outside rim of the disc should be round, which is not the same.

From a technical standpoint, few if any currently approved discs are radially symmetrical. It's just more obvious on the Epic. If a disc has raised lettering for patent and manufacturer ID, it's not radially symmetrical. Hotstamps make discs non-symmetrical. The gripper pads on Latitude 64 discs are not radially symmetrical. Flashing around the rim isn't technically part of the design and is usually not uniform but is tolerated as part of the manufacturing process. Granted, hotstamps and lettering don't have much height but without a standard for how high non-symmetrical elements can be, you can't fault the raised Turbo curl at this point.

My reaction after reading the agreement was get to work on removing the Epic as an approved disc too. Yay!



It shouldn't ... that disc has a lot of value. That rule would seem to stile innovation which is a negative in my book. I know Disccraft has a few disc that don't have Radial Symmetry too.

I think the outside should be a continuous circle disc shape just to prevent some one from making the "BuzzzSaw" and hurting someone.

I thought radial symmetry referred to the petal-like projections on the rim of the disc, not the swirl on the underside.


Chuck - what words would you use to convey a round disc with no projections on the rim?

'Uniform radius' I think would be the term to describe it...

circle of constant radius

Where can one find this PDGA memo? And has the disc been "disapproved" now?

One simple change to the way discs are measured would have eliminated anything but an outside rim that was circular. The current spec requires Jeff to make two diameter measurements at 90 degrees from each other that have to essentially be the same. In theory, an almost square disc could meet the current spec. I'm not sure where Jeff would position a disc like that for the flex test though.

Had the spec said to make diameter measurements at two random places, manufacturers would have to make the outside diameter circular since they wouldn't know where the two random measurements would be made.

Radially symmetrical means that everything along every radial line coming from the center of the disc would be the same. Repetitively symmetrical along the radius every X degrees would be like the Turbo-putt without the spiral.

Where can one find this PDGA memo? And has the disc been "disapproved" now?




Look at the link in the PDGA Announcements.

On the Home Page! Right where the ratings, and different things are listed.

I got some more info that the radial symmetry will ikely only apply to the top ofthe disc, not the rim or underside of the disc.

That is good cause that eipc is epic!

Considering the TSC hasn't discussed revising the specs yet, anything regarding where and if symmetry will be required is speculation at this point. And the Board would still have to approve or change whatever the TSC proposes.

Thanks Matt and Chuck - I usually go straight to the Discussion Board unless I'm looking for tournaments or tourney info. Chuck, really good seeing you, playing a round with you and talking this weekend. Wish I could have got my game up a few notches, but I definitely enjoyed it and got to play with a bunch of new faces.

How about a "mirrored" design. If cut in half (in a specific location) both halves would be a mirror image of the other.

This would hold true for the Epic, if cut at the shallowest to deepest part of the rim. For the thumbgrip type designs, if there are 3 thumbgrips you'd have to "split" one of the grips to give a mirror image. If there are multiples of 2 grip locations or other flight plane modifications, anywhere _should_ create a mirror image.

That seems a sensible solution.

Also, having a round outer diameter would be part of the equation.

my .02

I am curious as to why the PDGA chose to wait until December 31, 2008 to rescind approval.

From preliminary discussions, I think the TSC felt the integrity of the game hung on having a true disc being used for play in terms of a uniform outside diameter. Beyond that though, I believe there's more support for less conventional designs inside the rim on top and/or bottom. But we'll have to see how it shakes out in discussions and what latitude might be considered reasonable to allow for future changes/innovations.

I am curious as to why the PDGA chose to wait until December 31, 2008 to rescind approval.



They probably have a relationship with the manufacture. Rescinding approval now would economical effect the manufacture. It sounds like they wanted to come to a solution that was in the best interest of both the manufacture, those that already use the disc, and those stores that still have it for sale. Waiting allows all parties involved to have plan accordingly.

I am curious as to why the PDGA chose to wait until December 31, 2008 to rescind approval.




It says in the document. Quest already had manufactured many discs. This gives them the opportunity to make sure their already manufactured units sell thru. It was also a matter of ending approval after a calendar year so players who used them had a full season.

How are they going to sell the rest when everyone knows they won't be able to use them 1.5 years.

So no money was exchanged?

I think you see the full and complete agreement as posted.

How are they going to sell the rest when everyone knows they won't be able to use them 1.5 years.




how does everybody sell discs that will "NEVER" be thrown......


EBAY!!!!!!!!!

they'll be collectors items now and people will buy them JUST for that reason.....when they first came out people paid over 30 bucks each for them on ebay.....

they will all sell, plus the ones steve makes to sell now will sell as the "new improved" turbo putt

anyone remember classic coke?
that ruined coca-cola didn't it?

just wondering how many of you who posted here threw this disc.

to say that the hotstamp affects the symmetry of a disc is just being silly

We had mini-sized hotstamps on Worlds discs offset from center that I'm sure slightly unbalanced the disc when you figure we're measuring in grams and a piece of notebook paper weighs five grams.

just wondering how many of you who posted here threw this disc.



i threw it, and i own 1 of them also.

One way to look at the Turbo Putt, it's an instant collector item. Good for collectors, not sure about for Quest.

Doesn't Radial Symmetry only imply NOT oval or elliptical??

The radius is a straight line from center to edge. The PDGA guidelines to test diameter at 90 degrees apart is checking for equal radii (i.e. circle). Chuck's right though, a square could also pass this test as well as any number of odd shapes.

The thickness of the rim, lettering on the flight plate, or stamping on the inner rim have nothing to do with the radial symmetry. The stamping on top may affect arc length of the plate, and the mold letters inside the rim would affect center of disc to INNER rim radius. But inner rim radius is not used here, it's the outer rim, i.e. diameter of the disc, i.e. twice the radius.

I wonder how an elliptical disc would fly? I am also completely in favor of using technology to help the sport grow. But, most post production mods I've made to discs - cutting, shaving, holes in the flight plate, sections of rim removed, etc have all yielded the same - VERY understable discs. Any manufacturers have tests on an elliptical disc?

Radial Equality?

Matt, get back to work or I;m tellin'.

Doesn't Radial Symmetry only imply NOT oval or elliptical??




Nope. It's symmetry along the whole length of the radius not just its total length. You're thinking of Radial Equality, i.e. a circle.

ahh, so it's basically, a curve, that if revolved, would create a perfectly circular, perfectly uniform disc from center to edge, anywhere you test it?

I'm thinking about the defined radius of an object like a sphere or elliptoid. It has nothing to do with the arc length or anything on the surface it is simply measured center to edge. I guess it's just the interpretation of radial symmetry applied to both meaurement and weight, uniformity, etc. I'm looking at it only as a distance, straight line.

Either way, let's have technology improve our game. Anyone have experience throwing an elliptical disc?

Radial symmetry would normally mean that no matter where you cut a cross section through the center of the disc, all cross sections would look the same and have the same properties. In other words, density of the material would be the same at the same distance from the center. With lettering, rim width, hot stamps, gripper pads, even tiedye, most discs don't meet this criteria with some visually deviating more than others like the Epic and Turbo-Putt. From my standpoint, that's fine. However, I think the TSC needs to establish the maximum allowable range of the deviations that will still provide a wide enough range for experimentation and innovation.

Personally, I am amazed that the Epic was ever approved in the first place. While I absolutely love watching the things fly, it seems inherently wrong for a sport which is moving toward technical standardization to approve such an asymmetric disc. While Chuck's prior post might argue that the stitching or label for that matter on a baseball destroy its radial symmetry, you know d*** well that major league baseball would never approve a ball with an at-rest off-center center of gravity.

If the Epic was balancing on a pin in the dead center, wouldn't it balance in terms of overall weight distribution? I thought if you sliced it thru the middle along any diameter, each half would weigh the same? That's not an off center design assuming we don't count an off center sticker.

If the Epic actually can rest on pin, then I am somewhat suprised, just learned something, and withraw the center of gravity comment, but not my distaste for the messed up symmetry. Radial symmetry is not about halves, its about arcs. You should be able to select a wedge of any arc from anywhere on the disc, and have the complemetary one 180 degrees away have identical characteristics and dimensions.

Most discs don't exactly have that now so why would you expect it to be required?

I think it would be interesting to test a putter that's weighted off center so it wobbles as it spins into the chains. I think there's a possibility the chains would hold it better and it wouldn't tip and slip out as easy since the disc would cover more chain real estate.

The Epic couldn't be cut in half where both halves would be of equal weight but for one location.

That is if it's the same epic I have seen... You'd be cutting at the thickest and thinnest part of the rim.

I only saw it once several years ago and for some reason I thought it had a thicker rim on opposite sides and thinner rim on the other opposite sides 90 degrees away? Unfortunately, we don't get pictures of the discs when our TSC gets the updated approvals. I think I'll propose that be the case in the future.

http://g-ec2.images-amazon.com/images/I/41BTMTAQGCL._AA280_.jpg

Thanks. That might change my opinion regarding assymetical features. I think I lean toward more symmetry such as the left and right rim thicker and top and bottom rim thinner if you're going to vary features radially.

sprinterMatt is right the epic has bilateral symmetry, not radial. Only one plane will bisect mirror images. you could still balance it on a pin i imagine, just wouldn't be the center of the inner circle on the underside

I agree. I'm not sure what I think at this point. I'll be interested to hear what others on the committee have to say as we work toward an updated spec later this year.

The 10m brick is also not radially symmetric. It repeats its pattern every 30 degrees.

good call there