DGR Homework: parting line height and relative stabilities

[Jsw]

Sick discovery Marmoset - thanks for sharing.

[marmoset]

I am posting Jeronimo's pictures:

Ok, I said I would so here they are:

overstable striker on left, normal striker everyone knows and loves on right


overstable vision on left, understable vision on right



Remember, these are supposedly the SAME discs side by side. The noses should be tip to tip and CLEARLY you can see that is not the case. The Visions don't even resemble each other!

[victorb]

That ^ is exactly the difference between my strikers.

The one with the nose pulled up acts way more overstable for me, but I think that's because it's more difficult to throw it nose down.

[Timko]

I think there are 2 types of parting line difference.

The first is lateral difference. That's explained in the pictures above. I was doing some research on the Valk/Vike mistake of recent, and found an old Innova flight chart from 2000 that states that Domey discs are more understable, and flat discs are more overstable.

The 2nd is angular difference. This is the difference between the light and heavy star bosses. The cooling of the discs causes the parting line to no longer be perfectly straight, which pulls the parting line at the outer edge of the wing down. So the parting line only has a small difference, but the wing shape is changed.

[Lithicon]

Comparing two Pro Wraiths 175 and a Star Wraith 165
The two Pro's are slightly domier. One worn in, and the other is pretty new, only had a few rounds on it. The Star is slightly flatter, but worn in as much as the first Pro.
Comparing the two Pro's the newer is barely higher and still more stable but, I would assume this is to the other being worn in and taking more hits to things. makes sense.
Comparing the worn Pro and the worn Star, the Star is higher, but not pigishly over stable, but still more stable than the worn Pro.
Comparing the new Pro and the worn Star, The lines are very close to the same. The Pro I feel is still slightly more stable than the Star even though the Pro is domier. Perhaps the weight of the Star is what makes it less stable than a the New Pro.
-----------------------------------------------------
Comparing two DX Leopards and Champ Leopard all 150's
I found this at work, I have a pretty newer DX Leopard that is freakishly understable compared to a worn in DX leopard, couldn't figure out why. Perhaps this answers my question.
Comparing the two DX, the newer one is well below the parting line of the older one, older is much more stable.
Comparing Champ to new DX, DX is again, well below the the champ parting line and champ being way more stable.
Comparing the older DX to the Champ, they are very close, the champ barely higher and slightly more stable than the worn in DX.


I've thrown all these enough to know their flights and the parting line does seem to affect disc in the same mold. Quite the find. Very worthwhile it seems to fondle a disc before purchase. =.O

[marmoset]

Very worthwhile it seems to fondle a disc before purchase.

↑↑↑↑↑This is what I have realized.
Unfortunately I am a cheapskate so I like to use my 10% discount on the already low prices @ DGC.com. DGC is 700 miles away.

[PRES 10]

I have been paying attention to parting lines for 2 years know, it is by far the best way to tell the stablility of the disc without thowing it. Ive taken my beaten up dx teebird and tuned (bent) the wing up so the parting line is higher so i can keep it as my straight disc. This can only be done a few times as it can make the disc squirrely after to much plastic is removed.

Another thing to look for if the parting lines are the same is to see how much the underside of the wing is concave/convexed. the more concaved the more stable. This us normally pretty similar in premium plastics but in baseline they can vary alot.

[marmoset]

Another thing to look for if the parting lines are the same is to see how much the underside of the wing is concave/convexed. the more concaved the more stable.

Agreed, but I am not as prepared to talk about this aspect yet.

[tigel]

i just tried this on my two wraiths. The newer one is clearly more stable than the other one. however there is NO difference in line height. I'm sure it's because my understable one is beat to hell? Figured i'd post either way.

[Lithicon]

Yeah, that's why his testing was done with a control, the control being 2 newer disc.
Wear is pretty evident to flight in some models. In your case, I'd consider wear to be the factor.
Wear the second in as much as the first, and I'm sure the flight patterns will start to mimic.

What this points out as slight defects or mishaps in molds, that are either out of the manufactuers control, or just aren't monitored. Or just slight mold modifications in later disc.

[Jesse B 707]

this has held true on all of my drivers..........except the 2 stalkers i have i have a domier blue one and a flatter orange and while the parting line on the blue is higher the orange is a good deal beefier, maybe ive got a mutant or mismarked weights

[Star Shark]

That could be like the Firebird phenomenon where the flatter ones are more stable. That's why people love the 11x's.

[marmoset]

Question: has anyone seen 2 brand new discs (of the same mold, of course) with identical PLHs... one is domey the other is flat?

I haven't seen it but I thought I would ask all you guys to check your backup stacks anyways.

Just curious.

[SkaBob]

I tl;dr'ed this thread, so if I'm repeating someone, just ignore me and move on...

Parting line height changes because of how the disc cooled. If it's higher, it means the flight plate shrunk more than the ones with a lower parting line.

If the flight plate shrinks more, it pulls the angle of the wing upwards around the whole disc, causing the bottom of the disc to be more aggressively angled to the air when it flies. This will give the effect of having more of a notch than it might otherwise have.

eg- a Valk and a Teebird. If a Valk cools in the manner that causes it's parting line to be higher, the bottom of the wing is going to have an angle of attack more like that of the Teebird, and so it's going to fly more overstable (like a Teebird).

This is most readily apparent on Flicks, in my experience. Domey Flicks are significantly less overstable than Flat-topped Flicks. This defies conventional wisdom to a certain extent, because we've been saying domey = overstable for a while. In most cases it's true, up to a certain point where the angle of attack of the bottom of the wing gets to a certain point, and starts causing more of an effect than the dome would.

You do lose a good chunk of glide as that progresses even further, though. There isn't as much dome on top to help generate lift (not to mention the effect the disc wanting to dive to the left has on distance potential).

[RS39]

Question: has anyone seen 2 brand new discs (of the same mold, of course) with identical PLHs... one is domey the other is flat?

I haven't seen it but I thought I would ask all you guys to check your backup stacks anyways.

Just curious.

ESP Wasps, 4gr apart, noses are exact match, heavier one is shouldered up to the ring stamp, other is close to dead flat.