PLH- what it is and what it does.

I have been preaching PLH here on DGCR. People keep asking me what it is. Here is an explanation.


This is a picture that Anakha posted on DGR along time ago.

You see the thin horizontal line in the middle of the discs? That's the P arting L ine H eight (PLH). The parting line is the thin line of plastic that is accidentally left on the disc after it has been injection molded. It is accidental because ideally the molds will be machined with high enough tolerance that there will be no witness of where the mold separates. But in the real world, wear and tear will slightly round the edges of the mold halves. Plastic flows into the rounded off sections and voila! You have a visible parting line.


"Yeah, I hear you but... so what?"

Well... assuming the 2 discs in the picture above came from the exact same mold , the PLH will dictate how overstable the disc will be. Well, that's the extremely simplified way of stating it but that statement still holds up well in practice. I underlined "the exact same mold" because this is very important. No, San Marino Rocs and Rancho Rocs are not the same mold.


Take 2 Wizards. Put them nose to nose. The one with the higher PLH will be more overstable. Even if one is E plastic and one is SSS. If both discs pictured above were Wizards (they're not, one is last year's Ace Race putter), then the yellow disc on the right would be more overstable. That's all there is to it.

Take 2 Bosses and put them nose to nose similar to the putters in the picture. The one with the higher PLH will be more overstable than the one with the lower PLH. I have a Champ Boss and an R-Pro Boss. The PLH is almost 1/8th inch higher on the Champ; guess which is more overstable? Yes, there is a big difference between the weights. But the difference would still be huge if they weighed the same. Even with the 25 gram weight difference, if the lighter R-Pro had a higher PLH it would be more overstable than the Champ. It might not ACT as overstable because you could more easily reach the designed cruising speed of the disc. It is easier to accelerate a 1 pound object to 50 mph than a 20 pound object. Given the identical speed and spin between the 2 Bosses, the lighter disc but higher PLH would be more overstable.

Because of the discs geometry, the PLH will have a larger range of shift on discs with wider wings. This is commonly recognized. Flashes are known for wild inconsistency. Forces vary, Bosses vary, Katanas vary. Even Leopards (relatively thin rimmed driver) will have stablility variations but because the PLH can't shift as much the variations won't be as extreme. This is why Cyclones, GZs, TBs, EXs, XLs, etc. are "more consistant" from run to run when compared to Bosses.


"Okay, that's all fine and good but what practical application does this have for me?"

You can save money. Ever go to the store to buy a backup Boss? It might not fly at all how you wanted it to. Too overstable, too understable whatever. It is tough to do with beat discs but you can try to match your thrower's PLH to a new discc's PLH. It is better to take a measurement before you ever throw that disc. Yeah it's pretty nerdly but it would save money.

Also you can use this technique to pick out specific variations. The first time I bought a Roadrunner I knew I wanted most of the typical RR characteristics but I didn't want a really flippy one. I bought the highest PLH that PIAS had and I'm happy with it. I bought another one online and it is too flippy. The PLH is significantly lower. Not 1/8th of an inch like the Bosses, but every little fraction of a millimeter makes an appreciable difference.


So, to sum up (and I know you are sick of hearing this by now)...

THE HIGHER THE PLH, THE MORE OVERSTABLE THE DISC.

THE LOWER THE PLH, THE LESS OVERSTABLE THE DISC.

But they have to be the same mold.


EDIT: Sorry for any misspellings, I didn't proofread. My post was too long. "What is all this PLH mumbo-jumbo that I keep hearing from this nutcase?"I have been preaching PLH here on DGCR. People keep asking me what it is. Here is an explanation.This