DGR Homework: parting line height and relative stabilities

[jubuttib]

I do work at a disc golf store. I must just really suck at this haha. *cuts wrists* Next time mzuleger comes in I will have him show me what I am doing wrong.

Well there's the of chance that you're just extremely lucky and all the discs at the store (that you've checked) have been consistent!

Oh, and usually we're looking for rather small differences. A millimeter will be a significant difference. At least sometimes.

[rusch_bag]

I am working right now so I am going to go figure this shit out.

[rusch_bag]

Ok. Not that hard. I went and grabbed my bag too and looked at 2 wizards I have been driving with and they are from the same run and weight and whatnot, but I know one is more stable than the other and I just compared them and there is like a 3 mm difference between the 2. I also was looking at pro bosses vs champ and whatnot and you can really see a difference. Katanas vary a lot.

[Thatdirtykid]

I compared all of my forces recently hoping to find one less stable than the rest. Only 1 had a lower PLH than the rest (they are pretty consistent between plastics/runs) But the one with the lower flips up to flat easier, and if I throw close to flat it will helix well, while most still just go straight.

[marmoset]

Ok. Not that hard. I went and grabbed my bag too and looked at 2 wizards I have been driving with and they are from the same run and weight and whatnot, but I know one is more stable than the other and I just compared them and there is like a 3 mm difference between the 2. I also was looking at pro bosses vs champ and whatnot and you can really see a difference. Katanas vary a lot.

3mm is a lot, especially for a putter!
Yeah, the Katanas I have compared are all over the charts.

[jubuttib]

3mm is HUGE.

Katanas are almost notoriously inconsistent with PLH, probably because the super wide wing rarely shrinks consistently.

Also, R-Pro Bosses have at least a different core piece than other Bosses, might be a contributing factor. My 139 R-Pro Boss fits under my 171 Star Bosses wing. Same with my R-Pro Katana, it fits under my Startanas.

[marmoset]

...R-Pro Bosses have at least a different core piece than other Bosses...

Didn't know that; thanks for the heads up!

[matchu]

I talked with Dave about this a few years ago, and how a disc cools can affect the parting line as it shrinks. Sometimes they will put the disc on something while cooling to hold shape. Seasons of the year and different plastics, colors, weighting agents can all affect the distance of the parting line from the bottom of the disc.

[Bradley Walker]

I actually posted this exact subject like 5 years ago? I took two Cyclones and compared the noses on a glass table...

This also lead to the conclusion that the real reason a disc gets less stable with time is the fact that bottom of the disc is worn away with time...

This is a very good thread!!!! I am going to take my good Katana with me when I buy another!!! Good idea!!!

[jubuttib]

This also lead to the conclusion that the real reason a disc gets less stable with time is the fact that bottom of the disc is worn away with time...

It's part that, but from the studies people have done it's only a small part, and applies more to baseline putters and mids than drivers and premium discs. They've found that knocks a disc gets bend the wing down, lowering the PLH that way. The test discs flew very noticeably understable compared to the control discs, even though the wear they measured was minimal. The wing angle had changed pretty much though, and affected PLH.

[aerohusker]

I've had good luck removing or reducing the dome using the microwave. Take a proper size plate, placing a small amount of water, then disc (face down) add just enough water to cover inside surface, heat for 1-1.5 min. remove and lay on flat cool surface. You can take a little or a lot of dome out.

[victorb]

I've had good luck removing or reducing the dome using the microwave. Take a proper size plate, placing a small amount of water, then disc (face down) add just enough water to cover inside surface, heat for 1-1.5 min. remove and lay on flat cool surface. You can take a little or a lot of dome out.

Dome and parting line height characteristics aren't directly proportional to each other. Flattening a disc won't change the parting line height, so it can be assumed that dome doesn't affect disc stability as much as parting line height.

For instance, I have two predators from different runs that have similar domes. One has a much higher parting line height than the other. The high PLH predator files much more overstable than the other.

[jubuttib]

I've had good luck removing or reducing the dome using the microwave. Take a proper size plate, placing a small amount of water, then disc (face down) add just enough water to cover inside surface, heat for 1-1.5 min. remove and lay on flat cool surface. You can take a little or a lot of dome out.

Dome and parting line height characteristics aren't directly proportional to each other. Flattening a disc won't change the parting line height, so it can be assumed that dome doesn't affect disc stability as much as parting line height.

For instance, I have two predators from different runs that have similar domes. One has a much higher parting line height than the other. The high PLH predator files much more overstable than the other.

I'll have to disagree with you on that one. Flattening or increasing the dome can indeed affect the PLH. When I got my FR Axes I tried to give the green one a bit more dome (totally flat, and more understable than the orange moderately domey one). I succeeded, and actually gave it too much dome, it resembled one of the pink ones. I checked the PLH and it was now much higher than the orange ones, and had developed a proper fade (like the pink ones). I then flattened it again, back to totally flat, PLH was lower than the orange one, like it was originally. Then I again added dome, this time I was more careful and added only a bit, now it matched the orange both in dome and PLH.

They aren't directly related and flattening/adding dome won't always do anything to the stability, but anything can happen.

[aerohusker]

So its not so much the dome, it's the PLH that makes the diff?

I've have three Kraits, all diffrent dome heights, one was really 'domey' and flew like a meat hook, I heated it up, but took out too much dome, made it slightly concave, flew worse then a Momba, very understable.
Could reducing dome lower PLH? or is it a combo that determines stability? I actually think maybe the the 'dome' has more effect then the PLH?

[pask2155]

In my opinion I always go domey means more glide and tiny bit more over stable. Flat is less glide and tiny bit under stable. But these are very small minor differences. The plh is the big thing. But for me usually the domey discs for whatever reason seem to have a lower parting line. So I think most of the time ( this isn't treacly a rule of thumb to many variances) they go hand in hand.

Thoughts?