DGR Homework: parting line height and relative stabilities

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Re: DGR Homework: parting line height and relative stabilities

Postby marmoset » Wed Mar 24, 2010 10:23 am

Dave McCormack, owner of Gateway wrote:"The most recent runs of Sabre are less stable, but not JUST because of the lower PLH,, because of the smaller bead,,, which like the PLH, beads and concaves and rim depths are all also extremely important to the stability.

Baby blue Illusions are a perfect example of PLH and again YES, lowering this height is what we try to do when we run E Illusions. It can be done by a WIDE range of variables from temperature of polymer, Temperature of mold, speed of injection, pressure, hold time, how they are stacked on the table and a combination of any more,,,plus a combination of the above mentioned.
...
Several factors effect flight,,,, PLH is certainly one of them."

I had a conversation with Dave and he said he specifically tries to influence PLH to get desired flight characteristics.
Interesting.
I knew it could be done, I just didn't know anyone was actually doing it.
I asked if he could label the runs so we'd know the relative stability of the run but he said no way, Jose.
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Re: DGR Homework: parting line height and relative stabilities

Postby jubuttib » Wed Mar 24, 2010 10:46 am

Huh, I thought the main reason a bead increased stability was because it also increased PLH. It'd be nice to see two discs with the same PLH, one beaded and one not.
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Re: DGR Homework: parting line height and relative stabilities

Postby marmoset » Wed Mar 24, 2010 10:52 am

jubuttib wrote:Huh, I thought the main reason a bead increased stability was because it also increased PLH. It'd be nice to see two discs with the same PLH, one beaded and one not.

Yes, beads raise the PLH but beads also bias the weight further out which in turn increases the gyroscopicness of the disc.
One little change has a big effect on a disc.
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Re: DGR Homework: parting line height and relative stabilities

Postby discspeed » Wed Mar 24, 2010 11:04 am

marmoset wrote: but beads also bias the weight further out which in turn increases the gyroscopicness of the disc.


This depends on where they pulled the plastic out of to create the bead...For example, the Buzzz is more gyroscopic than a Wasp/Roc because its nose is a little thicker (weight on the outside of the wing) rather than having a bead on the inside of the wing. The Wasp/Roc have a thinner nose (outer edge of wing) and the plastic is instead in the bead.
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Re: DGR Homework: parting line height and relative stabilities

Postby marmoset » Wed Mar 24, 2010 12:30 pm

My comment was directed towards a beaded disc vs. the beaded version of the same disc.
Identical geometry except one has a bead.
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Re: DGR Homework: parting line height and relative stabilities

Postby jubuttib » Wed Mar 24, 2010 1:29 pm

marmoset wrote:My comment was directed towards a non-beaded disc vs. the beaded version of the same disc.
Identical geometry except one has a bead.

Fixed.
Parks wrote:If the posts on this forum are any indication, the PD is like a Teebird with sunshine coming out of its butthole so hard that it flies faster.
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Re: DGR Homework: parting line height and relative stabilities

Postby marmoset » Wed Mar 24, 2010 1:35 pm

jubuttib wrote:
marmoset wrote:My comment was directed towards a non-beaded disc vs. the beaded version of the same disc.
Identical geometry except one has a bead.

Fixed.

That's the second time today!
I gonna need to have you proofread all my posts...
Thanks again.
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Re: DGR Homework: parting line height and relative stabilities

Postby jubuttib » Wed Mar 24, 2010 1:46 pm

It's something I do instinctively and mostly just pisses people off. I'm just glad it's not bothering you. =)
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Re: DGR Homework: parting line height and relative stabilities

Postby BIF13 » Wed Mar 24, 2010 7:20 pm

marmoset wrote:My comment was directed towards a beaded disc vs. the beaded version of the same disc.
Identical geometry except one has a bead.


some one needs to post pics of a nuke and a nuke-x, same disc, just one has a bead.
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Re: DGR Homework: parting line height and relative stabiliti

Postby Hoey » Fri Jul 30, 2010 11:31 am

bump.

read up for those who haven't.
Throw discs, and forget about life for awhile...
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Re: DGR Homework: parting line height and relative stabiliti

Postby rusch_bag » Fri Jul 30, 2010 5:52 pm

I understand how all this works and whatnot, but every time I try using the plh to find a disc I just get frustrated. I have found it to be a bitch to see on the side of most discs and also I don't know if I just don't have a big enough selection to compare this too, but I have never seen the line be different on the same mold yet.
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Re: DGR Homework: parting line height and relative stabiliti

Postby marmoset » Fri Jul 30, 2010 7:51 pm

rusch_bag wrote:...I don't know if I just don't have a big enough selection to compare this too, but I have never seen the line be different on the same mold yet.

I thought you worked in a dg store?
It is much easier to see the PL on brand new discs. If you've thrown them then the flashing wears off/gets scraped off pretty quickly.
Also, the wider the wing the more drastically the PLH can shift. Bosses, Katanas, grooves, etc. will have a larger range of PLHs. Putters and mids will have a smaller range.
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Re: DGR Homework: parting line height and relative stabiliti

Postby jubuttib » Sat Jul 31, 2010 1:10 am

I'm not that sure the actual LINE is that important, I always just compare the whole edge.
Parks wrote:If the posts on this forum are any indication, the PD is like a Teebird with sunshine coming out of its butthole so hard that it flies faster.
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Re: DGR Homework: parting line height and relative stabiliti

Postby marmoset » Sat Jul 31, 2010 7:30 am

Correct.
The actual line has nothing to do with stability.
As it turns out, the line is just a readily visible indicator of the entire disc geometry. In theory, the line should rest in the exact same place on every disc that is pulled from that mold. But as each individual disc cools, the material shrinkage exerts stresses on the disc structure and causes deformations which result in departure from the geometry of the mold cavity. As the dome increases or decreases with cooling the wing angle will increase or decrease. As the wing is pulled upwards the inner rim wall slants more and more and would eventually- if the structure would allow- end up like a slanted Roc+ or Teebird+ wall.

Another force at work is how true the material holds the mold's radiuses like the one you find on the nose of the disc, the flight plate above the disc, and the entire dome in general. The more a plastic shrinks as it cools, the less it will end up looking like the mold cavity it was pulled from.

These angle changes and radius changes are the true culprits in specific disc stability. The PLH is just the easiest way I could fiind to quantify how much the geometry had changed. I have a new piece of equipment I have been visualizing. It will be cool when it is done. I will post pictures when I can.
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Re: DGR Homework: parting line height and relative stabiliti

Postby rusch_bag » Sat Jul 31, 2010 10:35 am

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.
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